Evaluation of microbial population dynamics in the co-composting of cow manure and rice straw using high throughput sequencing analysis

Insights into a Novel and Efficient Microbial Nest System for Treating Pig Farm Wastewater

A microbial nest system (MNS) represents a novel and efficient approach to treating solid-liquid mixtures from pig farming instead of the conventional method, which separates the solid and liquid at first using centrifugation before treating the solid and liquid. However, the key environmental factors influencing the efficiency of this system and the microbial structure are still not clear. This study aimed to elucidate the changes in an MNS considering physicochemical properties, spectral analysis, and correlations between microbial community structures and environmental factors during the treatment. The results showed that the MNS underwent three temperature stages during the treatment process of piggery slurry: a warming period, a high-temperature period, and a cooling period. In the high-temperature period, the most abundant bacterium was Bacillus, with a relative abundance of 22.16%, and Chaetomium dominated the fungal community with a relative abundance of 11.40%. Moreover, the moisture content, pH value, and electrical conductivity (EC) exhibited an increasing trend, whereas the carbon-to-nitrogen (C/N) ratio and the ratio of ammonia nitrogen to nitrate nitrogen (NH4+-N/NO3--N) showed a decreasing trend. The accumulation of humic acid and fulvic acid suggested that the humification process of organic matter was occurring. The moisture content and C/N ratio were identified as crucial factors influencing the bacterial and fungal community structures, respectively. This study provides a theoretical basis for enhancing the efficiency of piggery slurry treatment using an MNS and rational optimisation of the associated processes.

Analysis of microbial community potentially involved in carbon monoxide production in compost and its functional assessment: Utilized pathways, enzymes, and genes

Carbon monoxide (CO) is a valuable compound widely used in industry, and its biological production aligns with the bioeconomy principles. This study introduces a novel perspective by exploring biowaste composting as a potential source of CO production. Using 16S rDNA sequencing, microbial communities within two zones of a compost pile, with low (CO/L, 119 ppm) and high CO concentration (CO/H, 785 ppm), were characterized. The metabolic potential of microbial communities was investigated using PICRUSt2, an advanced tool for functional analysis. Results revealed higher alpha diversity in CO/H samples compared to CO/L, likely influenced by the lower temperature at the CO/H sampling site (50 °C vs. 62 °C in CO/L). Importantly, in the PCoA plots, samples clustered together depending on the sampling site. The microbial community composition was dominated by Bacilli (up to 98.8 % and 55.4 % of CO/L and CO/H samples, respectively). One of the key results was the detection of the Wood-Ljungdahl pathway, a metabolic route for CO production, in nearly all compost samples. This pathway was more abundant in CO/H samples (0.011-0.027 %) compared to CO/L samples (0.000-0.002 %). Moreover, 7 enzymes and 7 genes responsible for CO production and metabolism were detected in compost samples, suggesting that the observed CO formation is likely of biotic origin. The study for the first time underscored the potential of composting as a sustainable method for CO generation and validated PICRUSt2 as a reliable tool for uncovering biotic CO production mechanisms, offering valuable preliminary insights into the functional capabilities of microbial communities.

Investigating the inhibitory mechanism of methanogenesis during composting under the combined influence of amoxicillin and copper pollution

This study investigated the effects of different levels of combined amoxicillin and copper (Cu) pollution on the methanogenesis of microbial communities during aerobic composting of dairy manure. Three groups were established: the control group (CK), a low-level combined pollution group (L), and a high-level combined pollution group (H). As the level of pollution increased, carbohydrate metabolism decreased during the thermophilic phase of composting, while signal translation increased. Compared with the initial phase, functional genes related to the acetoclastic pathway decreased significantly in abundance during the thermophilic phase, and cdh had the lowest relative abundance among acetoclastic pathway with a decrease of 81.52%, 81.88%, and 84.73% in groups CK, L, and H, respectively. The cumulative methane emissions in group H decreased by 31.56% and 9.23%, respectively, compared with those from groups CK and L. These results contribute to understanding the effects of combined amoxicillin and Cu pollution on methane emissions during composting.

Upgrade from aerated static pile to agitated bed systems promotes lignocellulose degradation in large-scale composting through enhanced microbial functional diversity

Composting presents a viable management solution for lignocellulose-rich municipal solid waste. However, our understanding about the microbial metabolic mechanisms involved in the biodegradation of lignocellulose, particularly in industrial-scale composting plants, remains limited. This study employed metaproteomics to compare the impact of upgrading from aerated static pile (ASP) to agitated bed (AB) systems on physicochemical parameters, lignocellulose biodegradation, and microbial metabolic pathways during large-scale biowaste composting process, marking the first investigation of its kind. The degradation rates of lignocellulose including cellulose, hemicellulose, and lignin were significantly higher in AB (8.21%-32.54%, 10.21%-39.41%, and 6.21%-26.78%) than those (5.72%-23.15%, 7.01%-33.26%, and 4.79%-19.76%) in ASP at three thermal stages, respectively. The AB system in comparison to ASP increased the carbohydrate-active enzymes (CAZymes) abundance and production of the three essential enzymes required for lignocellulose decomposition involving a mixture of bacteria and fungi (i.e., Actinobacteria, Bacilli, Sordariomycetes and Eurotiomycetes). Conversely, ASP primarily produced exoglucanase and β-glucosidase via fungi (i.e., Ascomycota). Moreover, AB effectively mitigated microbial stress caused by acetic acid accumulation by regulating the key enzymes involved in acetate conversion, including acetyl-coenzyme A synthetase and acetate kinase. Overall, the AB upgraded from ASP facilitated the lignocellulose degradation and fostered more diverse functional microbial communities in large-scale composting. Our findings offer a valuable scientific basis to guide the engineering feasibility and environmental sustainability for large-scale industrial composting plants for treating lignocellulose-rich waste. These findings have important implications for establishing green sustainable development models (e.g., a circular economy based on material recovery) and for achieving sustainable development goals.

Biochar, phosphate, and magnesium oxide in seaweed and cornstarch dregs co-composting: Enhancing organic matter degradation, humification, and nitrogen retention

Seaweed waste, abundant and rich in plant-stimulating properties, has the potential to be transformed into valuable soil amendments through proper composting and utilization management. Given its low carbon-to-nitrogen ratio, co-composting seaweed with carbon-rich cornstarch dregs is an effective strategy. However, the potential application of co-composting largely depends on the efficiency of the composting and the quality of the product. This study explores the effects of adding 10 % corn stalk biochar to a co-composting system of seaweed and cornstarch dregs, alongside varying buffering capacities of phosphates (KH2PO4 and K2HPO4·3H2O-KH2PO4) and MgO, on the degradation efficiency of organic matter, nitrogen transformation, and humification. The results indicate that the addition of biochar and salts enhances the oxygen utilization rate (OUR) and cellulase activity during the thermophilic phase. Additionally, X-ray diffraction (XRD) and parallel factor analysis (PARAFAC) demonstrate more intense solubilization and transformation of proteinaceous substances, along with cellulose degradation. These processes are crucial for enhancing organic matter degradation and humification, significantly boosting degradation (with an increase of 28.6 % to 33.8 %) and humification levels (HA/FA increased by 37.1 % to 49.6 %). Specifically, groups with high buffering capacity significantly promote the formation of NO3--N and NH4+-N, and a higher degree of humification, creating an optimal environment for significantly improving nitrogen retention (increased by 4.80 %). Additionally, this treatment retains and slightly enhances the plant-stimulating properties of seaweed. These findings underscore the potential of integrating biochar with specific ratios of phosphates and MgO to enhance composting efficiency and product quality while preserving the plant-stimulating effects of seaweed.

Soil bacterial communities affected by land-use types in a small catchment area of the Balaton Uplands (Hungary)

Changes resulting from different tillage practices can affect the structure of microbial communities, thereby altering soil ecosystems and their functioning. The aim of this study was to explore and compare the physical, chemical properties and bacterial community composition of soils from different land use types (forest, grassland, vineyard, and arable field) in a small catchment. 16S rRNA gene-based amplicon sequencing was used to reveal the taxonomic diversity of summer and autumn soil samples taken from two different slope positions. The greater the anthropogenic impact was on the type of land use, the greater the change was in soil physical and chemical parameters. All sample types were dominated by the phyla Pseudomonadota, Acidobacteriota, Actinobacteriota, Bacteroidota and Verrucomicrobiota. Differences in the relative abundance of various bacterial taxa reflected the different land use types, the seasonality, and the topography. These diversity changes were consistent with the differences in soil properties.

Dynamic changes in and correlations between microbial communities and physicochemical properties during the composting of cattle manure with Penicillium oxalicum

BACKGROUND

Penicillium oxalicum is an important fungal agent in the composting of cattle manure, but the changes that occur in the microbial community, physicochemical factors, and potential functions of microorganisms at different time points are still unclear. To this end, the dynamic changes occurring in the microbial community and physicochemical factors and their correlations during the composting of cattle manure with Penicillium oxalicum were analysed.

RESULTS

The results showed that the main phyla observed throughout the study period were Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes, Halanaerobiaeota, Apicomplexa and Ascomycota. Linear discriminant analysis effect size (LEfSe) illustrated that Chitinophagales and Eurotiomycetes were biomarker species of bacteria and eukaryote in samples from Days 40 and 35, respectively. Bacterial community composition was significantly correlated with temperature and pH, and eukaryotic microorganism community composition was significantly correlated with moisture content and NH4+-N according to redundancy analysis (RDA). The diversity of the microbial communities changed significantly, especially that of the main pathogenic microorganisms, which showed a decreasing trend or even disappeared after composting.

CONCLUSIONS

In conclusion, a combination of high-throughput sequencing and physicochemical analysis was used to identify the drivers of microbial community succession and the composition of functional microbiota during cattle manure composting with Penicillium oxalicum. The results offer a theoretical framework for explaining microecological assembly during cattle manure composting with Penicillium oxalicum.

Isolation and identification of carbon monoxide producing microorganisms from compost

Carbon monoxide (CO) formation has been observed during composting of various fractions of organic waste. It was reported that this production can be biotic, associated with the activity of microorganisms. However, there are no sources considering the microbial communities producing CO production in compost. This preliminary research aimed to isolate and identify microorganisms potentially responsible for the CO production in compost collected from two areas of the biowaste pile: with low (118 ppm) and high CO concentration (785 ppm). Study proved that all isolates were bacterial strains with the majority of rod-shaped Gram-positive bacteria. Both places can be inhabited by the same bacterial strains, e.g. Bacillus licheniformis and Paenibacillus lactis. The most common were Bacillus (B. licheniformis, B. haynesii, B. paralicheniformis, and B. thermolactis). After incubation of isolates in sealed bioreactors for 4 days, the highest CO levels in the headspace were recorded for B. paralicheniformis (>1000 ppm), B. licheniformis (>800 ppm), and G. thermodenitrificans (∼600 ppm). High CO concentrations were accompanied by low O2 (<6%) and high CO2 levels (>8%). It is recommended to analyze the expression of the gene encoding CODH to confirm or exclude the ability of the identified strains to convert CO2 to CO.

Enhancing C and N turnover, functional bacteria abundance, and the efficiency of biowaste conversion using Streptomyces-Bacillus inoculation

Microbial inoculation plays a significant role in promoting the efficiency of biowaste conversion. This study investigates the function of Streptomyces-Bacillus Inoculants (SBI) on carbon (C) and nitrogen (N) conversion, and microbial dynamics, during cow manure (10% and 20% addition) and corn straw co-composting. Compared to inoculant-free controls, inoculant application accelerated the compost's thermophilic stage (8 vs 15 days), and significantly increased compost total N contents (+47%) and N-reductase activities (nitrate reductase: +60%; nitrite reductase: +219%). Both bacterial and fungal community succession were significantly affected by DOC, urease, and NH4+-N, while the fungal community was also significantly affected by cellulase. The contribution rate of Cupriavidus to the physicochemical factors of compost was as high as 83.40%, but by contrast there were no significantly different contributions (∼60%) among the top 20 fungal genera. Application of SBI induced significant correlations between bacteria, compost C/N ratio, and catalase enzymes, indicative of compost maturation. We recommend SBI as a promising bio-composting additive to accelerate C and N turnover and high-quality biowaste maturation. SBI boosts organic cycling by transforming biowastes into bio-fertilizers efficiently. This highlights the potential for SBI application to improve plant growth and soil quality in multiple contexts.

Black soldier fly larvae mitigate greenhouse gas emissions from domestic biodegradable waste by recycling carbon and nitrogen and reconstructing microbial communities

Black soldier fly larvae have been proven to reduce greenhouse gas emissions in the treatment of organic waste. However, the microbial mechanisms involved have not been fully understood. The current study mainly examined the dynamic changes of carbon and nitrogen, greenhouse gas emissions, the succession of microbial community structure, and changes in functional gene abundance in organic waste under larvae treatment and non-aeration composting. Thirty percent carbon and 55% nitrogen in the organic waste supplied were stored in larvae biomass. Compared to the non-aeration composting, the larvae bioreactor reduced the proportion of carbon and nitrogen converted into greenhouse gases (CO2, CH4, and N2O decreased by 62%, 87%, and 95%, respectively). 16S rRNA sequencing analysis indicated that the larvae bioreactor increased the relative abundance of Methanophaga, Marinobacter, and Campylobacter during the bioprocess, enhancing the consumption of CH4 and N2O. The metagenomic data showed that the intervention of larvae reduced the ratio of (nirK + nirS + nor)/nosZ in the residues, thereby reducing the emission of N2O. Larvae also increased the functional gene abundance of nirA, nirB, nirD, and nrfA in the residues, making nitrite more inclined to be reduced to ammonia instead of N2O. The larvae bioreactor mitigated greenhouse gas emissions by redistributing carbon and nitrogen and remodeling microbiomes during waste bioconversion, giving related enterprises a relative advantage in carbon trading.

Microbial mechanisms involved in negative effects of amoxicillin and copper on humification during composting of dairy cattle manure

Livestock manure often contains various pollutants. The aim of this study was to investigate how adding amoxicillin (AMX), Cu, and both AMX and Cu (ACu) affected humification during composting and the microbial mechanisms involved. The cellulose degradation rates were 16.96%, 10.86%, and 9.01% lower, the humic acid contents were 18.71%, 12.89%, and 16.78% lower, and the humification degrees were 24.72%, 24.16%, and 15.73% lower for the AMX, Cu, and ACu treatments, respectively, than the control. Adding AMX and Cu separately or together inhibited humic acid formation and decreased the degree of humification, but the degree of humification was decreased less by ACu than by AMX or Cu separately. The ACu treatment decreased the number of core bacteria involved in humic acid formation and decreased carbohydrate and amino acid metabolism during the maturing period, and thereby delayed humic acid formation and humification. The results support composting manure containing AMX and Cu.

Enhancing the carbon content of coal gangue for composting through sludge amendment: A feasibility study

Cocomposting coal gangue and sludge eliminates the challenge of utilizing coal gangue. However, there is limited understanding about the feasibility of cocomposting sludge and coal gangue, as well as the composting indicators, functional microorganisms, and safety risks involved. Therefore, this study evaluated the feasibility of enhancing carbon composting in coal gangue by incorporating sludge along with sawdust as a conditioner. Three laboratory-scale reactors were designed and labeled as T1 (20 % coal gangue, 60 % sludge, and 20 % sawdust), T2 (40 % coal gangue, 40 % sludge, and 20 % sawdust), and T3 (60 % coal gangue, 20 % sludge, and 20 % sawdust). Seed germination and plant growth assessments were conducted to ensure compost stability and assess phytotoxicity to cabbage (Brassica rapa chinensis L.) in terms of growth and biomass. The results indicated that the temperature, pH, EC and ammonia nitrogen of all three reactor conditions met the requirements for product decomposition. Composting was successfully achieved when the sludge proportion was 20 % (T3). However, when the sludge proportion was markedly high (T1), the harmlessness of the compost was reduced. The germination indices of T1, T2, and T3 reached 95 %, 122 %, and 119 % at maturity, respectively. This confirmed that the harmless cycle, which involved promoting condensation and aromatization, enhancing decay, and reducing composting time, was shorter in T2 and T3 than in T1. Coal gangue can also serve as a beneficial habitat for microorganisms, promoting an increase in their population and activity. Potting experiments in sandy soil revealed that the mechanism of action of compost products in soil included not only the enhancement of soil nutrients but also the improvement of soil texture. The results of this study suggest that using coal gangue as a raw material for composting is an efficient and environmentally friendly approach for producing organic fertilizers.

Integrating bioprocess and metagenomics studies to enhance humic acid production from rice straw

Rice straw burning annually (millions of tons) leads to greenhouse gas emissions, and an alternative solution is producing humic acid with high added-value. This study aimed to examine the influence of a microbial consortium and other additives (chicken manure, urea, olive mill waste, zeolite, and biochar) on the composting process of rice straw and the subsequent production of humic acid. Results showed that among the fungal species, Thermoascus aurantiacus exhibited the most prominent impact in expediting maturation and improving compost quality, and Bacillus subtilis was the most abundant bacterial species based on metagenomics analysis. The highest temperature, C/N ratio reduction, and amount of humic acid production (Respectively in lab 61 °C, 54.67%, 298 g kg-1 and in pilot level 65 °C, 72.11%, 310 g kg-1) were related to treatments containing these microorganisms and other additives except urea. Consequently, T. aurantiacus and B. subtilis can be employed on an industrial scale as compost additives to further elevate quality. Functional analysis showed that the bacterial enzymes in the treatments had the highest metabolic activities, including carbohydrate and amino acid metabolism compared to the control. The maximum enzymatic activities were in the thermophilic phase in treatments which were significantly higher than that in the control. The research emphasizes the importance of identifying and incorporating enzymatically active strains that are suitable for temperature conditions, alongside the native strains in decomposing materials. This strategy significantly improves the composting process and yields high-quality humic acid during the thermophilic phase.

Devitalization of Bacteria in Composted Cattle Manure with Natural Additives and Risk for Environment

Nowadays, there is an effort to improve the effectiveness of the composting process, supported by the addition of various supplements to reduce soil nutrition losses and increase soil remediation. The aim of this study was to examine the devitalization effect of natural additives like zeolite-clinoptilolite and its combination with hydrated lime in composted cattle manure on indicator and pathogen bacteria. The composting process was running in three static piles of cattle manure mixed with wheat straw (control, zeolite-lime, and zeolite) for 126 days. Composted manure substrates were determined for physicochemical (temperature, pH, nitrogen and phosphorus content, C/N, organic matter, and moisture) and microbiological analyses (Salmonella spp., indicator bacteria). The effects of additives were reflected in changes in physicochemical factors, e.g., an increase in temperature (<53 °C) or pH (<9.3). According to Pearson correlation, these changes (pH, Nt, Pt) resulted in a significant decrease (p < 0.001) of indicator bacteria (two or three orders) in zeolite pile or zeolite-lime pile. Die-off of Salmonella spp. in the zeolite-lime pile was indicated within 41 days; in other piles, this occurred on day 63. Our results can aid in further optimizing the composting of cattle manure in order to lower environmental pollution and the risk of human infection.

Effect of simplified inoculum agent on performance and microbiome during cow manure-composting at industrial-scale

A simplified inoculum agent, only comprising Bacillus subtilis and Aspergillus niger, was utilized for industrial-scale cow-manure composting to investigate its impact on composting performance and microbiome. Inoculants elevated the average and peak temperatures by up to 7 and 10 °C, respectively, during the thermophilic stage, reduced organic matter content, and raised germination index. Inoculation also extended the period of composting above 50 °C from 12 to 26 days. Sequencing unveiled significant shifts in microbial diversity, composition, and function. Aspergillus thrived during the mesophilic phase, potentially initiating composting, whereas Bacillus, Lysinibacillus, and Clostridium were enriched during the thermophilic stage. Metagenomic sequencing revealed an increased abundance of carbohydrate-active enzymes and glycometabolism-related genes responsible for lignocellulose degradation and heat generation after inoculation. These enriched microbes and functional genes contributed to organic matter degradation and temperature maintenance during thermophilic stage, expediting composting. This suggests the effectiveness of this simplified inoculum in industrial-level cow-manure composting.

Brown sugar as a carbon source can make agricultural organic waste compost enter the secondary thermophilic stage and promote compost decomposition

To enhance the efficiency of composting agricultural organic waste (AOW), this study aimed to examine the impact of inoculating tomato straw compost with two distinct microbial agents: ZymoZone (ZZ), a composite microbial agent derived from the straw compost and Effective Microorganisms (EM), a commercial microbial agent. Furthermore, in order to reactivate the microorganisms within the compost during the initial high temperature phase, 10% brown sugar was introduced as a carbon source. The objective of this addition was to assess its influence on the composting process. The findings revealed that compared to the control (CK) group, the ZZ and EM treatments extended the first high-temperature phase by 2 and 1 day, respectively. Furthermore, with the addition of 10% brown sugar, the ZZ and EM treatments remained in the second high-temperature phase for 8 and 7 days, respectively, while the CK treatment had already entered the cooling stage by then. Notably, the inoculation of microbial agents and the addition of brown sugar substantially augmented the activity of lignocellulose-related hydrolases, thereby promoting the degradation of lignocellulose in the ZZ and EM treatment groups. This was confirmed by FTIR analysis, which demonstrated that the addition of microbial agents facilitated the degradation of specific substances, leading to reduced absorbance in the corresponding spectra. XRD analysis further indicated a notable reduction in cellulose crystallinity for both the ZZ (8.00%) and EM (7.73%) treatments. Hence, the incorporation of microbial agents and brown sugar in tomato straw compost effectively enhances the composting process and improves the quality of compost products.

Characterization of microbial populations in two distinct dairy manure management systems: seasonal effect and implications for pollutant gases emissions

Following an increase in the demand for dairy products, higher quantities of manure are consequently produced, with the subsequent pollutant gas emission charge associated with its management. The 2 mostly used housing systems in the northeast of Spain, cubicles (CUB) and compost-bedded pack (CBP), entail different manure management techniques; thus, our main objective was to describe the microbiota present in the manure of both systems during 2 distinct climatic situations (winter, mean temperature of 6.2 °C; and summer, mean temperature of 36.4 °C). The secondary aim was to correlate these microbiological profiles with literature findings on the emission of certain well-known pollutant gases from manure. CBP showed to have higher alpha biodiversity as well as presenting a remarkable clustering by season but showed lower network complexity than CUB. Firmicutes/Bacteroidetes ratio was found superior in CUB, which also presented a significantly higher abundance of methanogenic genera belonging to Euryarchaeota phylum, such as Methanobrevibacter, Methanosaeta or Methanosarcina. On the other hand, CBP manure presented a significant presence of Corynebacterium, Pseudomonas, or Truepera, among other genera, which activity has been linked to nitrogen (N) transformation pathways in manure. The season also had a relevant role to play in the fluctuation of these populations within each housing system under study. These results show how microbial populations change when manure is differently managed, and how these variations can be related to the synthesis of certain pollutant gases in housing systems.

Comparison of bioaerosol release characteristics between windrow and trough sludge composting plants: Concentration distribution, community evolution, bioaerosolization behaviour, and exposure risk

Windrow and trough composting are two mainstream composting methods, but the effect of composting methods on bioaerosol release from sludge composting plants is unclear. The study compared the bioaerosol release characteristics and exposure risks between the two composting methods. The results showed that the bacterial aerosol concentrations in the windrow composting plant ranged from 14,196 to 24,549 CFU/m3, while the fungal aerosol concentrations in the trough composting plant reached 5874 to 9284 CFU/m3; there were differences in the microbial community structures between the two sludge composting plants, and the composting method had a greater effect on bacterial community evolution than on fungal community evolution. The biochemical phase was the primary source of the bioaerosolization behaviour of the microbial bioaerosols. In the windrow and trough composting plants, the bacterial bioaerosolization index ranged from 1.00 to 999.28 and from 1.44 to 24.57, and the fungal bioaerosolization index ranged from 1.38 to 1.59 and from 0.34 to 7.72, respectively. Bacteria preferentially aerosolized mainly in the mesophilic stage, while the peak of the fungal bioaerosolization index appeared in the thermophilic stage. The total non-carcinogenic risks for bacterial aerosols were 3.4 and 2.4, while those for fungi were 1.0 and 3.2 in the trough and windrow sludge composting plants, respectively. Respiration is the main exposure pathway for bioaerosols. It is necessary to develop different bioaerosol protection measures for different sludge composting methods. The results of this study provided basic data and theoretical guidance for reducing the potential risk of bioaerosols in sludge composting plants.

Inoculating exogenous bacterium Brevibacillus laterosporus ZR-11 at maturity stage accelerates composting maturation by regulating physicochemical parameters and indigenous bacterial community succession

Brevibacillus laterosporus ZR-11, a bio-control strain, was innovatively inoculated at maturity stage of composting to clarify its effect on physicochemical parameters and indigenous bacterial community structure in compost pile. Results revealed that ZR-11 inoculum rapidly increased pile temperature to 52 ºC and raised germination index (GI) value to beyond 85% on day 3, thereby achieving higher pile temperature and GI in the inoculated group than the non-inoculated group almost along maturity stage, and also decreased C/N ratio of the inoculated group to below 20 by composting end (day 8). Also, ZR-11 succeeded in colonizing compost pile along maturity stage. These suggested that ZR-11 as inoculum at maturity stage could accelerate compost maturation and have a potential to participate in bio-fertilizer production. High-throughput sequencing indicated that bacterial community structure experienced substantial succession in the inoculated and non-inoculated groups, and Firmicutes, Proteobacteria, and Actinobacteria were the dominant phyla in the two groups during maturity stage, with their abundances higher in the inoculated group. Saccharomonospora and Ammoniibacillus abundance increased on day 3 while Actinomadura abundance increased on day 6 in the inoculated group. As verified statistically, pile temperature and pH were key factors closely linked to dominant genera abundance, where Saccharomonospora and Ammoniibacillus abundance were positively correlated to pile temperature, while Actinomadura abundance was positively correlated to pile pH. Thus, it was inferred that ZR-11 inoculum could improve parameters such as temperature and pH to modify dominant genera abundance, thus regulating indigenous bacterial community succession, which might in turn promote compost maturation.

Fractional grey unequal-interval time-varying Lotka-Volterra model and its application for microbial communities in compost

Aerobic compost is an effective method for the treatment of livestock manure, which is usually accompanied by complex interspecific competition. Describing these competitive relationships through mathematical models can help understand the interaction of microorganisms and analyze the effect of exogenous additive to regulate the composting process. The common model for analyzing competition problem is the Lotka-Volterra model. However, the fixed parameters of the Lotka-Volterra model are not suitable to reflect the dynamic variations of the competitive relationship when the environmental conditions change during composting process. Therefore, this paper establishes a novel fractional grey unequal-interval time-varying Lotka-Volterra model. Firstly, a fractional grey derivate operator is proposed on the basis of the unequal interval of composting data and historical dependence of microbial growth. Secondly, considering the influence of temperature, a time-varying parameter matrix is defined to reflect the variation of competitive relationship at different composting phases, and it is estimated by forgetting factor recursive least squares. Thirdly, the optimal coefficients are optimized by grey prediction evolution algorithm. Finally, the proposed model is employed to analyze the chicken manure composting experiment. The results show that the proposed model has lower error criteria and more accurate trend of fitting curve than the other five existing models. The parameter matrix describes the dynamical variation of microbial competitive relationship in two taxonomic levels and reveals that effect of the exogenous additive is principally reacted in the thermophilic phase and the competitive advantage is shifted from Bacteroidota to Firmicutes after treatment with the exogenous additive.

Efficient carbon removal and excellent anti-clogging performance have been achieved in multilayer quartz sand horizontal subsurface flow constructed wetland for domestic sewage treatment

The present study aimed to investigate the application of a multilayer quartz sand substrate horizontal subsurface flow constructed wetland (HSFCW) for campus sewage treatment. It aimed to assess the pollutant removal efficiency and anti-clogging performance under the suggested maximum organic loading rate (250 g/m²/d). The results of the multilayer HSFCW (CW6) were compared to the mololayer HSFCW (CW1) for the removal of the chemical oxygen demand (COD), solid accumulation, and microbial communities. During operation, the combination conditions of high hydraulic loading rate (HLR) with low COD concentration were better for COD removal under a high organic loading rate (OLR) of 200-300 g/m²/d. The maximum removal rate reached 80.4% in CW6 under high HLR, which was 13.8% higher than that in CW1, showing better adsorption and biodegradation ability of organic matter. Impressive clogging resistance capacity was found in CW6 due to the lower contents of the insoluble organic matter (IOM) that are prone to clogging, indicating full degradation of organic matters, particularly IOM, in CW6 under high HLR. Less abundance of unclassified Chitinophagaceae (under low HLR), Pedobacter and Saccharibacteria_genera_incertae_sedis (under high HLR) in CW6, which contributed to aerobic membrane fouling, helped to prevent clogging. Moreover, Brevundimonas, Cloacibacterium, Citrobacter, Luteimonas contributed to IOM degradation, thus further enhancing the anti-clogging performance. In view of the better clogging resistance performance, the application of CW6 operated under high HLR and low COD concentrations was recommended to achieve economical, efficient, and steady COD removal for domestic sewage treatment in long-term operation.

Shifts in bacterial diversity characteristics during the primary and secondary fermentation stages of bio-compost inoculated with effective microorganisms agent

Microbial inoculation was an effective way to improve product quality of composting and solve traditional composting shortage. However, the effect mechanism of microbial inoculation on compost microorganisms remains unclear. Here, Shifts in bacterial community, metabolic function and co-occurrence network during the primary and secondary fermentation stages of bio-compost inoculated with effective microorganisms (EM) agent were analyzed by high-throughput sequencing and network analysis. Microbial inoculation promoted organic carbon transformation in early stage of secondary fermentation (days 27 to 31). The beneficial biocontrol bacteria were main dominant genera at the second fermentation stage. Microbial inoculation can be good for the survival of beneficial bacteria. Inoculation with microbes promoted amino acid, carbohydrate and lipid metabolism, and inhibited energy metabolism and citrate cycle (TCA cycle). Microbial inoculation could enhance complexity of bacterial network and enhance mutual cooperation among bacteria during composting.

Effect of the lignocellulolytic Psychrotroph Lelliottia sp. on bacterial community succession in corn straw compost

This study aimed to explore the effect of an inoculation, Lelliottia sp., on the corn straw compost's physico-chemical properties, composition, and the succession of bacterial community structure. The compost community composition and succession changed after Lelliottia sp. inoculation. Inoculation increased the bacterial community diversity and abundance in the compost to promote composting. The inoculated group entered the thermophilic stage on the first day, lasting 8 days. Judging the pile maturity based on the carbon:nitrogen ratio and germination index values, the inoculated group reached the maturity standard, which was 6 days faster than the control group. The relationship between environmental factors and bacterial communities was comprehensively analyzed using redundancy analysis. Temperature and carbon:nitrogen ratio were the main environmental factors driving the succession of bacterial communities, to provide basic information on the changes of physicochemical indexes and bacterial community succession in Lelliottia sp. inoculated maize straw composting, providing assistance for practical composting applications of this strain.

Bacterial dynamics and functions driven by biomass wastes to promote rural toilet blackwater absorption and recycling in an ectopic fermentation system

Due to high concentration of organic matter and the ease of disease transmission, blackwater pose a serious threat to both the environment and human health, especially in rural areas where wastewater treatment is dispersed. The reuse of biomass waste is also a difficult issue to be addressed urgently. In this study, an ectopic fermentation system (EFS) was used to treat toilet blackwater, and the effects of different biomass waste combinations on bacterial communities and functions during aerobic fermentation of blackwater were compared. The results showed that adding bran powder prolonged the high temperature period of 11 d, improved blackwater absorption capacity by 7.5% and was beneficial to microbial metabolic activities to enhance organic degradation. By contrast, the combination of corn straw and rice husk obtained abundant bacterial OTUs and diversity. Bacillus, Thermobifida and Thermopolyspora were the main microorganisms involved in the degradation of organic matter in EFS, and their abundance varied in different filler combinations. Bacterial communities were directly affected by environmental factors such as temperature, NH₄⁺-N and organic carbon as well as biomass materials during fermentation. This study revealed the role of corn straw, rice husk and bran powder in EFSs, provided new technical support for blackwater treatment and a new direction for the resource utilization of agricultural biomass waste.

Inoculating indoleacetic acid bacteria promotes the enrichment of halotolerant bacteria during secondary fermentation of composting

The secondary fermentation stage is critical for stabilizing composting products and producing various secondary metabolites. However, the low metabolic rate of mesophilic bacteria is regarded as the rate-limiting stage in composting process. In present study, two indoleacetic acid (IAA)-producing bacteria (Bacillus safensis 33C and Corynebacterium stationis subsp. safensis 29B) were inoculated to strengthen the secondary fermentation stage to improve the plant-growth promoting potential of composting products. The results showed that the addition of IAA-producing bacteria promoted the assimilation of soluble salt, the condensation and aromatization of humus, and the accumulation of dissolved organic nitrogen (DON) and dissolved organic carbon (DOC). The bioaugmentation strategy also enabled faster microbial community succession during the medium-late phase of secondary fermentation. However, the colonization of Bacillus and Corynebacterium could not explain the disproportionate increase of IAA yield, which reached up to 5.6 times compared to the control group. Deeper analysis combined with physicochemical properties and microbial community structure suggested that IAA-producing bacteria might induce the increase of salinity, which enriched halotolerant bacteria capable of producing IAA, such as Halomonas, Brachybacterium and Flavobacterium. In addition, the results also proved that it was necessary to shorten secondary fermentation time to avoid IAA degradation without affecting composting maturity. In summary, enhancing secondary fermentation of composting via adding proper IAA-producing bacteria is an efficient strategy for upgrading the quality of organic fertilizer.

Influence of Biochar on Physico-Chemical, Microbial Community and Maturity during Biogas Residue Aerobic Composting Process

With the rapid development of large and medium-sized biogas projects, the high-value utilization of anaerobic fermentation residues has become a hot spot in recent years. In this study, biogas residue from biogas engineering was used as composting raw material, and 0 (CK), 2.5% (T1), 5.0% (T2), 7.5% (T3), and 10.0% (T4) biochar was added to investigate its effects on physico-chemical properties, microbial populations, and maturity degree during the aerobic composting process. Results show that the addition of biochar shortens the time (3 days) to reach the high-temperature period, increases the composting temperature (63.8 °C) and germination index (GI), decreases the electrical conductivity (EC), reduces the loss of C and N elements, and increases the microbial population during composting. These results suggest that biochar can improve the maturity and fertility of compost products, and significantly regulate the structure and function of microbial communities during the composting process.

Effect of moisture content on the evolution of bacterial communities and organic matter degradation during bioaugmented biogas residues composting

Composting is an excellent way to recycle biogas residues into a stable, non-toxic agricultural end product. In this study, the dynamic changes of physical-chemical parameters and bacterial community in three groups of bioaugmentation composting systems at different moisture contents (MC) of 50% (MC50), 60% (MC60) and 70% (MC70) were monitored. The differences of bacterial communities in composts with different initial MC were compared, and the interaction between biological and non-biological parameters was also explored. The results revealed that after 30 days of composting, the biogas residues compost in MC60 reached highest temperature of 64 °C, total Kjeldahl nitrogen (TKN) of 2%, seed germination index (GI) of 110%, and the longest thermophilic period duration of 5 days (55 °C). Additionally, the result of high-throughput sequencing showed that the diversity of bacterial communities in MC60 was the highest, and the abundance of Actinobacteria (16.93-52.63%), Firmicutes (8.71-56.75%), and Proteobacteria (16.88-46.95%) in all groups were the highest at phylum level. The LEfSe analysis indicated that the abundance of Ochrobactrum and Cellulomonadaceae in MC60 was significantly (p < 0.05) higher than with other treatments. Moreover, canonical correspondence analysis (CCA) indicated thermophilic period duration is significantly (p < 0.05) positively correlated with Paenibacillus. Besides, it was found the relative abundance of Nocardiopsis and Georgenia has a significant (p < 0.01) correlation with the fertilizer efficiency of compost. These results showed that controlling the initial moisture content at 60% can improve the maturity and fertilizer efficiency of compost, and enable the bacteria beneficial to composting to gain the advantage of proliferation.

Membrane-covered composting significantly decreases methane emissions and microbial pathogens: Insight into the succession of bacterial and fungal communities

In this study, the effects of semipermeable membrane-covered on methane emissions and potential pathogens during industrial-scale composting of the solid fraction of dairy manure were investigated. The results showed that the oxygen concentration in the membrane-covered group (CT) was maintained above 10 %, and the cumulative methane emission in CT was >99 % lower than that in the control group (CK). Microbial analysis showed that the bacterial genus Thermus and the fungal genus Mycothermus were dominant in CT, and the richness and diversity of the bacterial community were greater than those of the fungal community. At the end of the composting, the relative abundance of potential bacterial pathogens in CT was 32.59 % lower than that in CK, and the relative abundance of potential fungal pathogens in each group was <2 %. Structural equation models revealed that oxygen concentration was a major factor influencing the bacterial diversity in CT, and the increase of oxygen concentration could limit methane emissions by inhibiting the growth of anaerobic bacteria. Therefore, membrane-covered composting could effectively improve compost safety and reduce methane emissions by regulating microbial community structure.

Performance exploration and microbial dynamics of urine diverting composting toilets in rural China

The ongoing "toilet revolution" in China provides new opportunities to improve the rural living environment and sanitation, and the introduction of new sanitation facilities such as urine diverting composting toilets (UDCTs) is conducive to the effective treatment and resource utilization of feces. This study revealed the degradation performance and microbial community dynamics of UDCTs and clarified the influence mechanism of fecal volume in aerobic composting treatment. The results showed that UDCTs could effectively decompose human feces, with an organic matter degradation rate of 25%⁓30%. The temperature, water content, NH₄⁺-N and nutrient accumulation were higher in the high fecal volume treatment than in the low fecal volume treatment. Bacterial community composition and structure in UDCTs varied with composting stage and fecal volume. The diversity and richness of bacterial community in compost were changed with different fecal volumes, but the dominant groups were similar. Redundancy analysis (RDA) showed that nitrogen and organic carbon were the main drivers of bacterial community changes during composting. Highly nutritious and non-phytotoxic compost products were suitable for agronomic uses. Based on these results, UDCTs can be an effective way to solve the problem of fecal pollution in rural areas, and fecal dosage is a potential influencing factor in the operation and maintenance of composting systems.

Rapid decomposition of rice straw by application of a novel microbial consortium and study its microbial community dynamics

Rice straw decomposition is an attractive solution to open-field burning but the traditional method has slow kinetics and takes 60-90 days to obtain mature compost. In this study, we propose to boost up the decomposition process by addition of a novel microbial consortium rich in lignocellulolytic microbes. C: N ratio of the compost reached 11.69% and degradation efficiency of cellulose and hemicellulose was found to be 64 and 87% respectively within 25 days. Lignocellulolytic activity of the microbial consortium was confirmed by plate and activity assay. These parameters clearly indicated that a mature compost was obtained in 25 days. The 16S rRNA gene amplicon sequencing and functional analysis of predicted genes indicated amino acid and carbohydrate metabolism as the major metabolic pathway during composting. The tertiary level of functional analysis revealed the major metabolic pathways in the bacterial communities as pentose phosphate pathway, glycolysis and tricarboxylic acid cycle.

Effects of di-n-butyl phthalate on aerobic composting process of agricultural waste: Mainly based on bacterial biomass and community dynamics analysis

Phthalic acid esters (PAEs) pollution has become a major environmental problem in agricultural waste composting. However, little information was available about the how the PAEs alter microbial processes during composting. This study investigated the effects of di-n-butyl phthalate (DBP) on bacterial biomass and community dynamics during composting. The results showed that a decreasing of DBP was observed from thermophilic phase and 43.26% of DBP was degraded after composting. The bacterial biomass and diversity during composting were reduced under DBP stress, so delaying the decomposition of organic matter. Moreover, the changes in bacterial community were observed since the thermophilic phase of DBP-contaminated composting. KEGG pathway analysis indicated that DBP stress decreased the relative abundance of the main metabolic pathways and inhibited compost maturation. Moreover, DBP stress had more significant correlation with the dominant bacteria. This work will expand the understanding of PAEs-contaminated organic waste composting and further control of PAEs pollutants.

Compositional and Functional Changes in Microbial Communities of Composts Due to the Composting-Related Factors and the Presence of Listeria monocytogenes

Listeria monocytogenes is a leading foodborne pathogen that can contaminate fresh produce in farm environment, resulting in deadly outbreaks. Composts contain a diversity of microorganisms, and some of them may be compost-adapted competitive exclusion microorganisms against L. monocytogenes. To understand interactions between compost microflora and the pathogen, both dairy- and poultry-wastes based composts (n = 12) were inoculated with L. monocytogenes, and then analyzed by next-generation sequencing approaches along with culturing methods. DNA extraction and enumeration of L. monocytogenes were performed at 0 and 72 h post-incubation at room temperature. The major bacterial phyla were identified as Firmicutes (23%), Proteobacteria (23%), Actinobacteria (19%), Chloroflexi (13%), Bacteroidetes (12%), Gemmatimonadetes (2%), and Acidobacteria (2%). The top three indicator genera enriched in different compost types were identified by LEfSe with LDA score > 2. The interactions between L. monocytogenes and indigenous microflora were limited as no significant changes in the dominant microbial members in compost ecosystem, but some discriminatory species such as Bacillus, Geobacillus, and Brevibacterium were identified by Random Forest analysis. Besides, changes in metabolic pathways and the increased abundance of bacteriocins category in the compost samples containing L. monocytogenes after 72 h postinoculation were revealed by metatranscriptomic sequencing. Taken together, the compost-related factors such as compost types, composting stages, and the collection farms are major drivers that affect compost microbial compositions, and the analysis of compost metagenome implied that interactions between L. monocytogenes and compost microflora may include competition for nutrients and the presence of antimicrobials. IMPORTANCE Listeria monocytogenes has been recognized as the etiological agent causing foodborne disease outbreaks, with fresh produce as vulnerable for contamination at even preharvest stage. Owing to the richness in microbial community, compost may mediate suppression of pathogens. In this study, the impact of compost-related factors and L. monocytogenes intrusion on dynamic changes in compost microbiome was investigated by next generation sequencing techniques. The compost-related factors such as compost types, composting stages, and the collection farms are major drivers that affect compost microbiome. The interactions between L. monocytogenes and compost microflora may include the competition for nutrients and the presence of antimicrobials produced by native compost microorganisms as potential competitive exclusion microorganisms. Findings from this study are important for the composting industry to understand the composition and functionality of microbial community in their products and help developing organic fertilizers fortified with anti-L. monocytogenes competitive exclusion microorganisms.

Succession of Microbial Community during the Co-Composting of Food Waste Digestate and Garden Waste

Microorganisms are of critical importance during the composting process. The aim of this study was to reveal the bacterial and fungal compositions of a composting pile of food waste digestate and garden waste, where the succession of the microbial communities was monitored using Illumina MiSeq sequencing. We explored the efficiency of composting of different microorganisms to judge whether the composting system was running successfully. The results showed that the composting process significantly changed the bacterial and fungal structure. Firmicutes, Proteobacteria, and Bacteroidota were the dominant phyla of the bacterial communities, while Ascomycota was the dominant phylum of the fungal communities. Moreover, the highest bacterial and fungal biodiversity occurred in the thermophilic stage. The physical and chemical properties of the final compost products conformed to the national standards of fertilizers. The efficient composting functional microbes, including Cladosporium, Bacillus and Saccharomonospora, emerged to be an important sign of a successfully operating composting system.

Quality assessment, safety evaluation, and microbiome analysis of night-soil compost from Lahaul valley of northwestern Himalaya

The Himalayan dry toilet system prevalent in the northwestern Himalaya is a traditional practice of converting human faeces into a compost-like soil amendment. The current study evaluated night-soil compost (NSC) for agricultural use by assessing the compost quality, safety, and microbiome properties. Based on the fertility and clean indices determined by the fertility and heavy metal parameters, NSC was categorized as good quality compost with high fertilizing potential and moderate concentration of heavy metals. With respect to pathogens, the faecal coliform levels in the NSC were categorized as safe according to the U.S. Environmental Protection Agency standards. The bacterial community structure based on 16S rRNA gene amplicons revealed a diverse taxonomy with 14 phyla and 54 genera in NSC. Compared to publicly available 16S rRNA gene amplicon data, NSC exhibited predominant phyla (Proteobacteria, Bacteriodetes, Actinobacteria, and Firmicutes) similar to human faeces, cattle manure, food waste compost, vermicompost, and activated sludge. However, statistically, NSC was distinct at the genus level from all other groups. Additionally, pathogenic bacteria with antimicrobial resistance (AMR) genes in the NSC metagenome were determined by performing a standalone BLASTN against the PATRIC database. The analysis revealed 139 pathogenic strains with most pathogens susceptible to antibiotics, indicating lower AMR in the predicted strains. The phytotoxicity of NSC with Pisum sativum var. AS-10 seeds showed a germination index of > 85%, indicating NSC's non-harmful effects on seed germination and root growth. Overall, NSC from Himalayan dry toilets can be used as a soil amendment for food and non-food plants.

Effect of attapulgite on heavy metals passivation and microbial community during co-composting of river sediment with agricultural wastes

This paper investigated the effects of attapulgite addition on the physicochemical processes, heavy metal transformation, and microbial community during the composting of agricultural wastes and sediment. In addition, the correlation between environmental factors, heavy metals (HMs), and microbial community was also assessed by redundancy analysis (RDA). The results showed that pile B with attapulgite addition entered the thermophilic phase earlier and lasted longer than pile A as the control group. The reduction in the bioavailability of HMs (Cr, Cd, and Zn) was also greater in pile B, and the passivation of HMs was ranked as Cd > Zn > Cr. The relative abundance of phylum Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria was the highest throughout the composting process. Furthermore, the RDA showed that the bacterial community composition was significantly correlated with temperature and C/N ratio in pile A, while significantly correlated with organic matter and pH in pile B. And the addition of attapulgite facilitated the conversion of HMs into more stable fractions by Pseudomonas. The study would provide a reference for the application of attapulgite to remediate the river sediment polluted by HMs.

Effect of micro-aerobic conditions based on semipermeable membrane-covered on greenhouse gas emissions and bacterial community during dairy manure storage at industrial scale

This study evaluated the greenhouse gas emissions of solid dairy manure storage with the micro-aerobic group (MA; oxygen concentration <5%) and control group (CK; oxygen concentration <1%), and explained the difference in greenhouse gas emissions by exploring bacterial community succession. The results showed that the MA remained the micro-aerobic conditions, which the maximum and average oxygen concentrations were 4.1% and 1.9%, respectively; while the average oxygen concentrations of the CK without intervention management was 0.5%. Compared with the CK, carbon dioxide and methane emissions in MA were reduced by 78.68% and 99.97%, respectively, and nitrous oxide emission was increased by almost three times with a small absolute loss, but total greenhouse gas emissions decreased by 91.23%. BugBase analysis showed that the relative abundance of aerobic bacteria in CK decreased to 0.73% on day 30, while that in MA increased to 6.56%. Genus MBA03 was significantly different between the two groups (p < 0.05) and was significantly positively correlated with carbon dioxide and methane emissions (p < 0.05). A structural equation model also revealed that the oxygen concentration and MBA03 of the MA had significant direct effects on methane emission rate (p < 0.001). The research results could provide theoretical basis and measures for directional regulation of greenhouse gas emission reduction during dairy manure storage.

Bacteria in (vermi)composted organic wastes mostly survive when applied to an arable soil cultivated with wheat (Triticum sp. L.)

Composting and vermicomposting are an environmentally friendly way to reduce pathogens in organic wastes and generate a valuable product that provides nutrients for crops. However, how the bacterial community structure changes during these different processes and if the bacteria applied with the (vermi)composted products survive in an arable cultivated soil is still largely unknown. In this study, we monitored how the bacterial community structure changed during conditioning, composting with and without Eisenia fetida, and when the end-product was applied to arable soil cultivated with wheat Triticum sp. L. The organic wastes used were biosolid, cow manure, and a mixture of both. Large changes occurred in the relative abundance of some of the most abundant bacterial genera during conditioning, but the changes were much smaller during composting or vermicomposting. The bacterial community structure was significantly different in the organic wastes during conditioning and (vermi)composting but adding E. fetida had no significant effect on it. Changes in the relative abundance of the bacterial groups in the (vermi)composted waste applied to the arable soil cultivated with wheat were small, suggesting that most survived even after 140 days. As such, applying (vermi)composted organic wastes not only adds nutrients to a crop but also contributes to the survival of plant growth-promoting bacteria found in the (vermi)compost. However, putative human pathogens found in the biosolid also survived in the arable soil, and their relative abundance remained high but mixing the biosolid with cow manure reduced that risk. It was found that applying (vermi)composted organic wastes to an arable soil not only provides plant nutrients and adds bacteria with plant growth-promoting capacities, but some putative pathogens also survived.

Insights on dissolved organic matter and bacterial community succession during secondary composting in residue after black soldier fly larvae (Hermetia illucens L.) bioconversion for food waste treatment

Black soldier fly larvae (Hermetia illucens L. BSFL) bioconversion is a promising biotechnology for food waste treatment. However, the separated residues still do not meet criteria for use as land application biofertilizers. In this work, we investigated a full-scale BSFL bioconversion project to explore features of dissolved organic matter (DOM) and its associated responses of bacterial community succession in residue during secondary composting. Data showed that the concentrations of total nitrogen and ammonium nitrogen decreased by 11.8% and 22.6% during the secondary composting, respectively, while the nitrate nitrogen concentration increased 18.7 times. The DOM concentration decreased by 69.1%, in which protein-like, alcohol-phenol, and biodegradable aliphatic substances were metabolized by bacteria during the thermophilic phase together with the accumulation of humus-like substances, resulting in an increase in the relative concentration of aromatic compounds. The structure of the bacterial community varied at different stages of the bioprocess, in which Bacteroidetes, Actinobacteria, Proteobacteria, and Firmicutes were the dominant bacterial phyla. Lysinibacillus, Pusillimonas, and Caldicoprobacter were found to be key contributors in the degradation and formation of DOM. The DOM concentration (33.4%) and temperature (17.7%) were the prime environmental factors that promoted succession of the bacterial community. Through bacterial metabolism, the structural stability of DOM components was improved during the composting process, and the degrees of humification and aromaticity were also increased. This study depicted the dynamic features of DOM and the associated bacterial community succession in residue during secondary composting, which is conducive with the reuse of BSFL residue as biofertilizer for agriculture.

Microecological insight to fungal structure and key fungal communities regulating nitrogen transformation based on spatial heterogeneity during cow manure composting by multi-angle and multi-aspect analyses

Composting is the mainstream technology for the treatment of agricultural solid waste, but limited efforts were made to investigate fungal composition and its contributions to nitrogen transformation in different depths of compost. In this study, spatial distributions of fungi were analyzed using high throughput sequencing by multi-angle analyses, and the key fungal communities determining nitrogen transformation were quantified and identified by multi-aspect analyses during cow manure composting. Multi-angle analyses showed that fungal structure, biomarkers and trophic mode composition varied in different layers, revealing that spatial heterogeneity is the distinctive attribute of composting system. Ascomycota and Basidiomycota were dominant phyla during composting, the two phyla peaked in top and bottom layer respectively. At mesophilic stage, Tremellales, and unclassified Ascomycota (order) were biomarkers in top and middle layer respectively, and so were Remersonia, Pyrenochaetopsis, and Wallemia in bottom layer by LEfSe analysis. Based on multi-aspect analyses, Unclassified Dothideomycetes mainly affected NH₄⁺-N transformation both in top (1.2816***) and middle layers (1.1726*). Trichocladium asperum (0.9536***) and Zopfiella (-0.9484***) mainly affected TN transformation in top layer. Guehomyces pullulans (-0.9684**) and Preussia (-1.0508**) regulated NO₃^--N transformation in middle layer. Thermomyces lanuginosus (0.7127***) and Typhula sp. UW973129 (0.7298***) were the key species promoting TN and C/N transformation in bottom layer, respectively. Interestingly, different fungal communities showed a complex network interaction driving nitrogen transformation, and the abundance of microbial community could be conducive to characterizing nitrogen transformation in the vertical space of composting.

Structure of the manure resistome and the associated mobilome for assessing the risk of antimicrobial resistance transmission to crops

In this study, the impact of bovine and poultry manure on the quantitative and qualitative composition of antibiotic resistance genes (ARGs) and the environmental mobilome associated with antimicrobial resistance in soil and crops was determined with the use of next generation sequencing methods. The aim of the study was to perform a metagenomic analysis of manure to estimate the risk of the transmission of ARGs and bacterial drug resistance carriers to fertilized soil and crops. The total copy number of ARGs was nearly four times higher in poultry manure (555 ppm) than in bovine manure (140 ppm), and this relationship was also noted in fertilized soil. Poultry manure induced a much greater increase in the concentrations of ARGs in the soil environment (196.4 ppm) than bovine manure (137.8 ppm) immediately after supplementation. The application of poultry manure led to the highest increase in the abundance of genes encoding resistance to tetracyclines (9%), aminoglycosides (3.5%), sulfonamides (3%), bacitracin (2%), chloramphenicol (2%), and macrolide-lincosamide-streptogramin antibiotics (1%). Heavy metals were stronger promoters of antibiotic resistance in the environment than antibiotics. Antibiotics exerted a greater influence on maintaining the diversity of ARGs than on increasing their abundance in soil. Large quantities of insertion sequences (IS), including those associated with the mobility of ARGs in the population of ESKAPEE pathogens, are introduced to soil with manure. These IS remain stable for up to several months, which indicates that manure, in particular poultry manure, significantly increases the risk of rapid ARG transfer to the environment. Manure also largely contributes to an increase in the diversity of the resistome and mobilome in the metagenome of bacteria isolated from crops. Bacteria of the phylum Proteobacteria appear to play a major role in the transmission of multiple ARGs in crops grown for human and animal consumption.

Bacterial and fungal community dynamics during different stages of agro-industrial waste composting and its relationship with compost suppressiveness

Composting is an advantageous and efficient process for recycling organic waste and producing organic fertilizers, and many kinds of microorganisms are involved in obtaining quality compost with suppressive activity against soil-borne pathogens. The aim of this work was to evaluate the main differences in the effects of three composting piles on the whole bacterial and fungal communities of baby-leaf lettuce crops and to determine the specific communities by high-throughput sequencing related to suppressiveness against the soil-borne plant pathogen Pythium irregulare- (P. irregulare). Compost pile A was composed of 47% vineyard pruning waste, 34% tomato waste and 19% leek waste; pile B was composed of 54% vineyard pruning waste and 46% tomato waste; and pile C was composed of 42% vineyard pruning waste, 25% tomato waste and 33% olive mill cake. The temperature and the chemical properties of the piles were monitored throughout the composting process. In addition, the potential suppressive capacity of the three composts (C_A, C_B and C_C) against P. irregulare in baby-leaf lettuce was assessed. We found that the bacterial community changed according to the composting phases and composting pile and was sensitive to chemical changes throughout the composting process. The fungal community, on the other hand, did not change between the composting piles and proved to be less influenced by chemical properties, but it did change, principally, according to the composting phases. All composts obtained were considered stable and mature, while compost C_C showed higher maturity than composts C_A and C_B. During composting, the three piles contained a greater relative abundance of Bacterioidetes, Proteobacterias and Actinobacterias related to the suppression of soil-borne pathogens such as Pythium irregulare. Composts C_A and C_B, however, showed higher suppressiveness against P. irregulare than compost C_C. Deeper study showed that this observed suppressiveness was favored by a higher abundance of genera that have been described as potential suppressive against P. irregulare, such as Aspergillus, Penicillium, Truepera and Luteimonas.

Effects of Turning Frequency on Ammonia Emission during the Composting of Chicken Manure and Soybean Straw

Here, we investigated the impact of different turning frequency (TF) on dynamic changes of N fractions, NH3 emission and bacterial/archaeal community during chicken manure composting. Compared to higher TF (i.e., turning every 1 or 3 days in CMS1 or CMS3 treatments, respectively), lower TF (i.e., turning every 5 or 7 days in CMS5 or CMS7 treatments, respectively) decreased NH3 emission by 11.42-18.95%. Compared with CMS1, CMS3 and CMS7 treatments, the total nitrogen loss of CMS5 decreased by 38.03%, 17.06% and 24.76%, respectively. Ammonia oxidizing bacterial/archaeal (AOB/AOA) communities analysis revealed that the relative abundance of Nitrosospira and Nitrososphaera was higher in lower TF treatment during the thermophilic and cooling stages, which could contribute to the reduction of NH3 emission. Thus, different TF had a great influence on NH3 emission and microbial community during composting. It is practically feasible to increase the abundance of AOB/AOA through adjusting TF and reduce NH3 emission the loss of nitrogen during chicken manure composting.

Composting and its application in bioremediation of organic contaminants

This review investigates the findings of the most up-to-date literature on bioremediation via composting technology. Studies on bioremediation via composting began during the 1990s and have exponentially increased over the years. A total of 655 articles have been published since then, with 40% published in the last six years. The robustness, low cost, and easy operation of composting technology make it an attractive bioremediation strategy for organic contaminants prevalent in soils and sediment. Successful pilot-and large-scale bioremediation of organic contaminants, e.g., total petroleum hydrocarbons, plasticizers, and persistent organic pollutants (POPs) by composting, has been documented in the literature. For example, composting could remediate >90% diesel with concentrations as high as 26,315 mg kg^−a of initial composting material after 24 days. Composting has unique advantages over traditional single- and multi-strain bioaugmentation approaches, including a diverse microbial community, ease of operation, and the ability to handle higher concentrations. Bioremediation via composting depends on the diverse microbial community; thus, key parameters, including nutrients (C/N ratio = 25–30), moisture (55–65%), and oxygen content (O₂ > 10%) should be optimized for successful bioremediation. This review will provide bioremediation and composting researchers with the most recent finding in the field and stimulate new research ideas.

Evolution of physicochemical properties and bacterial community in aerobic composting of swine manure based on a patent compost tray

The objective of this study was to explore the changes in physicochemical properties and bacterial community during swine manure composting with a new compost tray (CT). The results showed that the organic matter (OM), moisture content (MC), and C/N decreased. The total Kjeldahl nitrogen (TKN), P₂O₅, K₂O and humic acids (HAs) contents of the compost increased. The properties of the final compost product comply with the requirements of regulation except for the moisture according to NY/T 525-2012. Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes were the major phyla during the composting. Genus Terrisporobacter played a key role in degrading organic (OM). The content of K₂O was main factors driving the succession of bacterial communities. These findings shed some novel lights into the dynamic changes of physicochemical propertied and their impact on bacterial community in a composting process.

New insight into the impact of moisture content and pH on dissolved organic matter and microbial dynamics during cattle manure composting

Composting is an effective way to treat agricultural waste, whereas inappropriate initial conditions could cause lower maturity and system instability. In this study, the dissolved organic matter dynamics and microbial community succession of cattle-manure composting were investigated under different initial moisture content (MC) and pH of raw material. The results indicated that the extended duration of thermophilic phase and the highest GI (germination index) value of final product were observed at matrix 60% MC and pH 8.5 (AT2 treatment). Microbial analysis showed that the succession of bacterial and fungal community was significantly influenced by total carbon (TN), pH and MC (P < 0.05). The relationship between microbial community and fluorescence regional integration (FRI) parameters demonstrated that Thermobifida (bacterial genus), Mycothermus and Thermomyces (fungal genera) were positively correlated with P_{V, n} (the integral aera of Region V). This study could provide a potential strategy for large-scale industrial application of compost.

The addition of sawdust reduced the emission of nitrous oxide in pig manure composting by altering the bacterial community structure and functions

Although composting, a measure to dispose agricultural waste, is widely accepted and applied, specific knowledge of microbially driven effects on nitrous oxide (N₂O) emissions during composting remains limited. Here, we monitored the impact of sawdust on N₂O emissions during pig manure composting. The results suggested that adding sawdust to the compost improved the compost temperature and reduced N₂O emissions. The addition of sawdust significantly altered the bacterial community structure and enhanced community turnover during the composting process. The addition of sawdust significantly reduced the relative abundance of denitrification and ureolysis, while increasing the relative abundance of nitrogen fixation. Specifically, adding sawdust may reduce N₂O emissions by reducing the relative abundance of Salinithrix, Truepera, Azomonas, Iamia, Silanimonas, Phycisphaera, and Gp21 during the thermophilic and mature phases of the composting period.

Efficiency and mechanism of a vermicompost additive in enhancing composting of swine manure

Vermicompost was used as an additive in swine manure composting to investigate the expression of bacterial functional genes on nutrients biotransformation. Three treatments with vermicompost compositions of 10%, 20%, and 30% in swine manure were set up. Raw manure was used as the control. The thermophilic period increased to 12 days, the NH₄⁺ -N/NO₃^- -N ratio decreased to 0.85, and the germination index (GI) increased to 166% after vermicompost addition. Furthermore, higher relative abundances of Firmicutes were observed in the substrate during the initial stages of experiment. The abundance of the dominant phylum Proteobacteria and its related pathogenic genera Acinetobacter and Stenotrophomonas decreased in the thermophilic stage while the potentially beneficial genera Actinomadura and Chryseolinea increased. The expression of primary functional genes associated with the metabolism of carbohydrates, amino acids, xenobiotics, and fatty acids was enhanced during the thermophilic phase. Besides, most dominant genera showed strengthened correlations with NO₃^--N and GI, which were the strongest environmental factors for bacterial communities. Network analysis revealed a new metabolic pathway associated with dominant genera Pseudomonas, Acinetobacter, Stenotrophomonas, and Oceanobacter, whose abundance increased with vermicompost addition. Collectively, the results of this study indicate that vermicompost can promote composting efficiency by increasing the potentially beneficial bacteria, decreasing pathogenic bacteria, and enhancing the metabolic capacity of bacterial communities.

Dynamics of bacterial and archaeal communities along the composting of tannery sludge

The process of composting has been proposed as a biological alternative to improve the quality of tannery sludge (TS) by the action of microbial communities. However, there is limited knowledge about the dynamic of these microbial communities during the composting process. This study assessed the responses of bacterial and archaeal communities during TS composting using the 16S rRNA sequencing. The composting process occurred within 90 days, and samples of compost were collected on day 7 (d7; mesophilic stage), 30 (d30; thermophilic stage), 60 (d60; cooling stage), and 90 (d90; maturation stage). The results showed a succession of microbial phyla during the composting with enrichment of Synergistetes, WS1, and Euryarchaeota at the mesophilic stage, while at the thermophilic stage, there was an enrichment of Hydrogenedentes, WPS-2, Chloroflexi, and Deinococcus-Thermus. At the cooling stage, there was an enrichment of Kiritimatiellaeota, and at the maturation stage, there was an enrichment of Entotheonellaeota, Dadabacteria, Nitrospirae, Dependiatiae, and Fibrobacteres. When analyzing the drivers influencing microbial communities, Cr and pH presented more negative correlations with general phyla. In contrast, S, C, K, temperature, and N presented more positive correlations, while Ni, Cd, and P showed fewer correlations. According to niche occupancy, we observed a decreased proportion of generalists with a consequently increased proportion of specialists following the composting process. This study showed that different stages of the composting present a specific microbial community structure and dynamics, which are related to some specific composting characteristics.

Moisture-Induced Pattern of Gases and Physicochemical Indices in Corn Straw and Cow Manure Composting

This study investigated the altering effect of moisture on the emission pattern of gases and the evolutionary dynamics of physicochemical indices in corn straw and cow manure composting. Exploring this effect was reasonable to unravel the use of moisture as a cheap alternative to control gaseous emissions and improve the final properties of compost. The nutrient dynamics of the compost showed 21.6% losses in total organic carbon content, with a 33.3% increase in total nitrogen content at the end of composting. All the gases (CH4, CO2, N2O and NH3) yielded a common emission pattern despite the differences in moisture content. Except for CH4, the peak and stable emission periods of all the gases were observed on the 5th day (thermophilic phase) and after the 27th day (late mesophilic phase) of composting, respectively. Emission reductions of 89%, 91%, 95% and 100% were recorded for CH4, CO2, N2O and NH3, respectively, during the late mesophilic phase of composting. From the study, the 65% moisture content was efficient in reducing the loss rate of the gasses and nutrient contents of the compost. This study would enable farmers to channel organic residues generated into compost while minimizing pollution and nutrient losses associated with the composting process.

Planifilum fulgidum Is the Dominant Functional Microorganism in Compost Containing Spent Mushroom Substrate

The extensive accumulation of spent mushroom substrate (SMS) owing to the large-scale production of edible fungi is causing environmental problems that cannot be ignored. Co-composting is a promising method for agricultural and animal husbandry waste disposal. In this study, the composition and function of microbial communities in the process of cattle manure–maize straw composting with SMS addition were compared through an integrated meta-omics approach. The results showed that irrespective of SMS addition, the predominant fungi were Ascomycota, while the dominant bacteria were Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. High temperature promoted the evolution from Gram-negative bacteria (Bacteroides, Proteobacteria) to Gram-positive bacteria (Firmicutes, Actinomycetes). The composting process was accelerated by SMS addition, and the substrate was effectively degraded in 14 days. Metaproteomics results showed that the dominant microorganism, Planifilum fulgidum, secreted large amounts of S8, M17, and M32 proteases that could degrade macromolecular protein substrates in the presence of SMS. Planifilum fulgidum, along with Thermobifida fusca and Melanocarpus albomyces, synergistically degraded hemicellulose, cellulose, and protein. In addition, the dominant microorganisms related to the initial raw materials such as Pichia, Lactobacillus in the microbial agent and Hypsizygus in SMS could not adapt to the high-temperature environment (>60 °C) and were replaced by thermophilic bacteria after 5 days of composting.