Dynamic change of bacterial community during dairy manure composting process revealed by high-throughput sequencing and advanced bioinformatics tools

From waste to protein: a new strategy of converting composted distilled grain wastes into animal feed

Distilled grain waste (DGW) is rich in nutrients and can be a potential resource as animal feed. However, DGW contains as much as 14% lignin, dramatically reducing the feeding value. White-rot fungi such as Pleurotus ostreatus could preferentially degrade lignin with high efficiency. However, lignin derivatives generated during alcohol distillation inhibit P. ostreatus growth. Thus, finding a new strategy to adjust the DGW properties to facilitate P. ostreatus growth is critical for animal feed preparation and DGW recycling. In this study, three dominant indigenous bacteria, including Sphingobacterium thermophilum X1, Pseudoxanthomonas byssovorax X3, and Bacillus velezensis 15F were chosen to generate single and compound microbial inoculums for DGW composting to prepare substrates for P. ostreatus growth. Compared with non-inoculated control or single microbial inoculation, all composite inoculations, especially the three-microbial compound, led to faster organic metabolism, shorter composting process, and improved physicochemical properties of DGW. P. ostreatus growth assays showed the fastest mycelial colonization (20.43 μg·g-1 ergosterol) and extension (9 mm/d), the highest ligninolytic enzyme activities (Lac, 152.68 U·g-1; Lip, 15.56 U·g-1; MnP, 0.34 U·g-1; Xylanase, 10.98 U·g-1; FPase, 0.71 U·g-1), and the highest lignin degradation ratio (30.77%) in the DGW sample after 12 h of composting with the three-microbial compound inoculation when compared to other groups. This sample was relatively abundant in bacteria playing critical roles in amino acid, carbohydrate, energy metabolism, and xenobiotic biodegradation, as suggested by metagenomic analysis. The feed value analysis revealed that P. ostreatus mycelia full colonization in composted DGW led to high fiber content retention and decreased lignin content (final ratio of 5% lignin) but elevated protein concentrations (about 130 g·kg-1 DM). An additional daily weight gain of 0.4 kg/d was shown in cattle feeding experiments by replacing 60% of regular feed with it. These findings demonstrate that compound inoculant consisting of three indigenous microorganisms is efficient to compost DGW and facilitate P. ostreatus growth. P. ostreatus decreased the lignin content of composted DGW during its mycelial growth, improving the quality of DGW for feeding cattle.

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.

Tire materials disturb transformations of nitrogen compounds and affect the structure of biomass in aerobic granular sludge reactors

Tire materials (TMs) present a notable hazard due to their potential to release harmful chemicals and microplastics into the environment. They can infiltrate wastewater treatment plants, where their effects remain inadequately understood, raising concerns regarding their influence on treatment procedures. Thus, this study investigated the impact of TMs in wastewater (10, 25, 50 mg/L) on wastewater treatment efficiency, biomass morphology, and microbial composition in aerobic granular sludge (AGS) reactors. TM dosage negatively correlated with nitrification and denitrification efficiencies, reducing overall nitrogen removal, but did not affect the efficiency of chemical-oxygen-demand removal. The presence of TMs increased the diameter of the granules due to TM incorporation into the biomass. The most frequently leached additives from TMs were N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, benzothiazole (BTH), and 2-hydroxybenzothiazole. In the treated wastewater, only BTH and aniline were detected in higher concentrations, which indicates that tire additives were biodegraded by AGS. The microbial community within the AGS adapted to TMs and their chemicals, highlighting the potential for efficient degradation of tire additives by bacteria belonging to the genera Rubrivivax, Ferruginibacter, and Xanthomonas. Additionally, our research underscores AGS's ability to incorporate TMs into biomass and effectively biodegrade tire additives, offering a promising solution for addressing environmental concerns related to TMs.

Physico-chemical assessment of on-farm bioconversion of organic waste in dairy farms in context to sustainability and circular bioeconomy

On a milk-producing dairy farm, milk production is correlated with manure production and the number of cattle, and manure is widely used as a soil fertilizer. However, excessive dairy manure production is linked with greenhouse gas emissions and water quality issues. On-farm planning of manure storage and application to enhance soil nutrients are essential in a circular economy to reduce environmental impact, where manure is not landfilled and incinerated. Instead, it creates a nutrient resource for crops and soil. Dairy manure, which is rich in nutrients, is a valuable fertilizer that contains many nutrients such as nitrogen (N), organic matter (OM), phosphorous (P), Potassium (K) and micronutrients. In this work, a pilot field research was conducted between 2016 and 2018 in various parts of California, USA (San Joaquin Valley, Sacramento Valley, Shasta Cascade, and the North Coast of California) to assess physio-chemical characteristics of solid fractions of dairy manure among various dairy farms. A total of 156 samples were collected from the gut (n = 107) and toe (n = 49) of the manure piles across California for determining total solid (TS), volatile solid (VS), temperature, moisture content and carbon-nitrogen ratio (C: N). Here, using the observations of field study and analysis, we show that C: N, OM and MC of solid fractions of dairy manure vary significantly among dairy farms. The average C: N ratio of manure (26-32) among various regions was close to an ideal C: N value of 24:1 for soil microbes to stimulate nutrient release to crops. Manure pH ranged between 7.0 and 8.0, which was close to an optimal pH range for common crops (6.0-8.0). Moreover, considering less cost and surplus availability, manure will likely continue providing a cost-effective organic fertilizer resource compared to commercial chemical fertilizers.

Microbial diversity in dairy manure environment under liquid-solid separation systems

In dairy manure, a wide array of microorganisms, including many pathogens, survive and grow under suitable conditions. This microbial community offers a tremendous opportunity for studying animal health, the transport of microbes into the soil, air, and water, and consequential impacts on public health. The aim of this study was to assess the impacts of manure management practices on the microbial community of manure. The key novelty of this work is to identify the impacts of various stages of manure management on microbes living in dairy manure. In general, the majority of dairy farms in California use a flush system to manage dairy manure, which involves liquid-solid separations. To separate liquid and solid in manure, Multi-stage Alternate Dairy Effluent Management Systems (ADEMS) that use mechanical separation systems (MSS) or weeping wall separation systems (WWSS) are used. Thus, this study was conducted to understand how these manure management systems affect the microbial community. We studied the microbial communities in the WWSS and MSS separation systems, as well as in the four stages of the ADEMS. The 16S rRNA gene from the extracted genomic DNA of dairy manure was amplified using the NovoSeq Illumina next-generation sequencing platform. The sequencing data were used to perform the analysis of similarity (ANOSIM) and multi-response permutation procedure (MRRP) statistical tests, and the results showed that microbial communities among WWSS and MSS were significantly different (p < 0.05). These findings have significant practical implications for the design and implementation of manure management practices in dairy farms.

Continuous thermophilic composting of distilled grain waste improved organic matter stability and succession of bacterial community

Continuous thermophilic composting (CTC) is potentially helpful in shortening the composting cycle. However, its universal effectiveness and the microbiological mechanisms involved are unclear. Here, the physicochemical properties and bacterial community dynamics during composting of distilled grain waste in conventional and CTC models were compared. CTC accelerated the organic matter degradation rate (0.2 vs. 0.1 d-1) and shortened the composting cycle (24 vs. 65 d), mainly driven by the synergism of bacterial genera. Microbial analysis revealed that the abundance of Firmicutes was remarkably improved compared to that in conventional composting, and Firmicutes became the primary bacterial phylum (relative abundance >70 %) during the entire CTC process. Moreover, correlation analysis demonstrated that bacterial composition had a remarkable effect on the seed germination index. Therefore, controlling the composting process under continuous thermophilic conditions is beneficial for enhancing composting efficiency and strengthening the cooperation between bacterial genera.

Influence of microbial community succession on biodegradation of municipal sludge during biodrying coupled with photocatalysis

A 20-day sludge biodrying process was coupled with photocatalysis to improve biodrying efficiency and investigate the effect of photocatalysis on biodegradation. After biodrying, the moisture content in the coupled photocatalytic group (TCA) and the control group (TUCA) decreased from 63.61% to 50.82% and 52.94%, respectively, and the volatile solids content decreased from 73.18% to 63.42% and 64.39%, respectively. Neutral proteinase activity decreased by 9.38% and 28.69%, and lipase activity decreased by 6.12% and 26.17%, respectively, indicating that photocatalysis helped maintain neutral proteinase and lipase activities. The Chao1 and Shannon indices showed that photocatalysis increased fungal diversity and reduced bacterial richness and diversity. The β diversity clustering analysis indicated that the bacterial community structure during the thermophilic phase in TCA differed from that in TUCA. The Kyoto Encyclopedia of Genes and Genomes annotation showed that photocatalysis has the potential to promote the synthesis and degradation of ketone bodies. Biodrying coupled with photocatalysis can improve the dewatering of sludge without negatively affecting biodegradation.

Antibiotic resistance gene profiles and evolutions in composting regulated by reactive oxygen species generated via nano ZVI loaded on biochar

In this study, nano zero-valent iron loaded on biochar (BC-nZVI) was analyzed for its effects on antibiotic resistance genes (ARGs) in composting. The results showed that BC-nZVI increased reactive oxygen species (ROS) production, and the peak values of H2O2 and OH were 22.95 % and 55.30 % higher than those of the control group, respectively. After 65 days, the relative abundances of representative ARGs decreased by 56.12 % in the nZVI group (with BC-nZVI added). An analysis of bacterial communities and networks revealed that Actinobacteria, Proteobacteria, and Firmicutes were the main hosts for ARGs, and BC-nZVI weakened the link between ARGs and host bacteria. Distance-based redundancy analysis showed that BC-nZVI altered the microbial community structure through environmental factors and that most ARGs were negatively correlated with ROS, suggesting that ROS significantly affected the relative abundance of ARGs. According to these results, BC-nZVI showed potential for decreasing the relative abundance of ARGs in composting.

Feedstock optimization with rice husk chicken manure and mature compost during chicken manure composting: Quality and gaseous emissions

This study investigated the impact of mature compost input on compost quality, greenhouse gases (GHGs, i.e. methane and nitrous oxide) and ammonia emissions during chicken manure and rice husk chicken manure co-composting. The experiment used different volumes of mature compost: 10% (T1), 20% (T2), and 30% (T3) to replace rice husk chicken manure. Results showed that mature compost enhanced compost maturity by promoting the activities of Bacillus, Caldicoprobacter, Thermobifida, Pseudogracilibacillus, Brachybacterium, and Sinibacillus. Compared to CK, T1, T2, and T3 reduced NH3 emission by 32.07%, 33.64%, and 56.12%, and mitigated 14.97%, 16.57%, and 26.18% of total nitrogen loss, respectively. Additionally, T2 and T3 reduced CH4 emission by 40.98% and 62.24%, respectively. The N2O emissions were positive correlation with Lactobacillus, Pseudogracilibacillus and ammonium nitrogen (p < 0.05), while T2 reducing total greenhouse effects. Therefore, replacing rice husk chicken manure with 20% mature compost is an efficient and promising approach for composting.

Treatment Options for Municipal Solid Waste by Composting and Its Challenges

Recovery and recycling of municipal solid waste biodegradable fraction (50-55%) are essential for attaining sustainability and a circular economy. Among organic waste treatment methods, composting is used to recycle organic fractions of waste. However, only 10-12% of municipal solid waste is utilized for composting treatment due to a lack of segregation practices and process challenges, including long process periods, odorous and greenhouse gas emissions, nitrogen loss, and low compost quality, which hinders large-scale practice. The current review paper discusses the challenges of composting treatment and its possible solutions. Various strategies were explored to address these challenges, such as utilizing microbial inoculum, additives, and optimization of physicochemical parameters. It also emphasizes the application of metagenomics for exploring key species. The knowledge about the microbial community and biochemical pathways (genome mining) can be exploited for the improvement of treatment efficiency.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01087-4.

Dynamics of Bacterial Diversity and Functions with Physicochemical Properties in Different Phases of Pig Manure Composting

Bacteria are key drivers in regulating ecosystem functions, and understanding the diversity and dynamic changes in bacteria in composting is very important for optimizing compost. This study investigated the structure, composition, and function of bacterial communities in alkaline pig manure compost using Miseq sequencing, PICRUSt2. The ACE and Chao1 indices of the bacterial communities in various phases were significantly different. Bacterial communities of alkaline pig compost were different from neutral and acidic swine manure compost, and there were 438 genera of common bacteria in various stages. The main bacterium was the phylum Firmicutes. There were six genera, including Romboutsia, Clostridium, Terrisporobacter, norank_f_Marinococcaceae, Saccharomonospora, and unclassified_f_Bacillaceae, that were significantly correlated (p < 0.05), or even extremely significantly correlated (p < 0.001), with the physicochemical properties. TOC, moisture, C/N, and Tem were the key factors that caused changes in bacterial communities in composting. PICRUSt2 analysis showed that there were seven functional groups: metabolism (45.02-48.07%), environmental information processing (15.25-16.00%), genetic information processing (16.97-20.02%), cellular processes (3.63-4.37%), human diseases (0.71-0.82%), organismal systems (0.66-0.77%), and unclassified (13.93-14.36%). This study will provide a reference for improving bacteria growth and reproduction conditions in pig manure composting, optimizing the process, and improving the efficiency of composting.

Aerated Static Pile Composting for Industrial Biowastes: From Engineering to Microbiology

This work demonstrated the feasibility of an industrial-scale aerated static pile composting system for treating one of the common biowastes-soybean curd residue. The mixing ratios of the feedstock were optimized to achieve a carbon-nitrogen ratio and a moisture level in the ranges of 25-35 and 60-70%, respectively. This open-air composting system required 6-7 months to obtain a mature compost. Solvita and seed germination tests further confirmed the maturity of the compost, with 25% compost extract concentration yielding the best germination index in the absence of phytotoxicity. The bacterial and fungal compositions of the compost piles were further examined with metagenomic analysis. Thermoactinomyces spp., Oceanobacillus spp., and Kroppenstedtia spp. were among the unique bacteria found, and Diutina rugosa, Thermomyces dupontii, and Candida taylorii were among the unique fungi found in the compost piles, suggesting the presence of good microorganisms for degrading the organic biowastes.

The contribution of microbial shikimic acid to humus formation during organic wastes composting: a review

Microbial shikimic acid is an important intermediate metabolite in the synthesis of aromatic amino acids which are precursors for forming humus during composting process. Generally, the pathways producing shikimic acid and its downstream products are collectively referred as shikimic acid pathway (SKP). Microbial SKP can produce phenols, and tyrosine. Pyrogallol is the precursor of phenols. And, tyrosine can form an ammoniated monomer. Therefore, regulation of SKP can promote shikimic acid production, which is beneficial in promoting humus production and humification. However, SKP present in microbial cells is distinctive because of providing precursors for humification process, which needs to be recognized during composting. Due to the different structures of various organic wastes, it is difficult to control the SKP efficiency and shikimic acid production. Therefore, it is valuable to review the synthesis of shikimic acid by microorganisms and propose how to promote SKP during different materials composting. Furthermore, we have attempted to illustrate the application of metabolites from SKP in forming humus during organic waste composting. Finally, a series of regulating methods has been outlined to enhance microbial SKP, which are effective to promote humus aromatization and to improve humus formation during different materials composting.

Bacterial community dynamics and co-occurrence network patterns during different stages of biochar-driven composting

Bacterial communities were dynamically tracked at four stages of biochar-driven sheep manure pile composting, and the co-occurrence networks with keystone taxa were established. The succession of bacterial community obvious varied during the composting process, Proteobacteria predominant in initial stage (39%) then shifted into Firmicutes in thermophilic (41%) and mesophilic (27%) stages, finally the maturation stage dominant by Bacteroidota (26%). Visualizations of bacterial co-occurrence networks demonstrate more cooperative mutualism and complex interactions in the thermophilic and mesophilic phases. Noticeably, the 7.5 and 10% biochar amended composts shown highest connections (736 and 663 total links) and positive cooperation (97.37 and 97.13% positive link) as well as higher closeness centrality and betweenness centrality of keystone taxa. Overall, appropriate biochar addition alters bacterial community succession and strengthens connection between keystone taxa and other bacteria, with 7.5 and 10% biochar amended composts has intense mutualistic symbiosis among bacterial communities.

Physicochemical and bacterial changes during composting of vegetable and animal-derived agro-industrial wastes

This study investigates the impact of different agro-industrial organic wastes (i.e., sugarcane filter cake, poultry litter, and chicken manure) on the bacterial community and their relationship with physicochemical attributes during composting. Integrative analysis was performed by combining high-throughput sequencing and environmental data to decipher changes in the waste microbiome. The results revealed that animal-derived compost stabilized more carbon and mineralized a more organic nitrogen than vegetable-derived compost. Composting enhanced bacterial diversity and turned the bacterial community structure similar among all wastes, reducing Firmicutes abundance in animal-derived wastes. Potential biomarkers indicating compost maturation were Proteobacteria and Bacteroidota phyla, Chryseolinea genus and Rhizobiales order. The waste source influenced the final physicochemical attributes, whereas composting enhanced the complexity of the microbial community in the order of poultry litter > filter cake > chicken manure. Therefore, composted wastes, mainly the animal-derived ones, seem to present more sustainable attributes for agricultural use, despite their losses of C, N, and S.

Different ratios of raw material triggered composting maturity associated with bacterial community co-occurrence patterns

Exploring the ecological function of potential core bacteria for high-efficiency composting can provide a fundamental understanding of the role of composting bacterial communities. Mushroom residue and kitchen garbage at different ratios (N1: 1/1, N2: 1/2) of dry weight were tested to investigate the key ecological role of the core bacteria responsible for producing mature compost. N1 had a peak temperature of 75.0 °C which was higher than N2 (68.3 °C). Other key composting parameters (carbon to nitrogen ratio (C/N) and germination index (GI)) also indicated that N1 achieved higher compost maturity. Rice seedlings experiments also further validated this conclusion. Putative key bacterial taxa (Thermobifida, Luteimonasd, Bacillus, etc.) were positively associated with the GI, indicating a substantial contribution to composting maturity. Co-occurrence network analysis revealed the ecological function of potentially beneficial core bacteria promoted cooperation among the bacterial community. The putative core bacteria in N1 may affect composting efficiency. Our findings reveal the mechanism of potential core bacteria throughout the compost maturity phases.

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.

Valorizing kitchen waste to produce value-added fertilizer by thermophilic semi-continuous composting followed by static stacking: Performance and bacterial community succession analysis

To explore an effective decentralized kitchen waste (KW) treatment system, the performance and bacterial community succession of thermophilic semi-continuous composting (TSC) of KW followed by static stacking (SS) was studied. A daily feeding ratio of 10% ensured stable performance of TSC using an integrated automatic reactor; the efficiencies of organic matter degradation and seed germination index (GI) reached 80.88% and 78.51%, respectively. SS for seven days further promoted the quality of the compost by improving the GI to 91.58%. Alpha- and beta-diversity analyses revealed significant differences between the bacterial communities of TSC and SS. Firmicutes, Actinobacteria, Chloroflexi, Gemmatimonadetes, and Myxococcota were dominant during the TSC of KW, whereas the members of Proteobacteria and Bacteroidetes responsible for product maturity rapidly proliferated during the subsequent SS and ultimately dominated the compost with Firmicutes and Actinobacteria. These results provide new perspectives for decentralized KW treatment using TSC for practical applications.

Antibiotic and heavy metal resistance genes in sewage sludge survive during aerobic composting

Municipal sewage sludge has been generated in increasing amounts with the acceleration of urbanization and economic development. The nutrient rich sewage sludge can be recycled by composting that has a great potential to produce stabilized organic fertilizer and substrate for plant cultivation. However, little is known about the metals, pathogens and antibiotic resistance transfer risks involved in applying the composted sludge in agriculture. We studied changes in and relationships between heavy metal contents, microbial communities, and antibiotic resistance genes (ARGs), heavy metal resistance genes (HMRGs) and mobile genetic elements (MGEs) in aerobic composting of sewage sludge. The contents of most of the analyzed heavy metals were not lower after composting. The bacterial α-diversity was lower, and the community composition was different after composting. Firmicutes were enriched, and Proteobacteria and potential pathogens in the genera Arcobacter and Acinetobacter were depleted in the composted sludge. The differences in bacteria were possibly due to the high temperature phase during the composting which was likely to affect temperature-sensitive bacteria. The number of detected ARGs, HMRGs and MGEs was lower, and the relative abundances of several resistance genes were lower after composting. However, the abundance of seven ARGs and six HMRGs remained on the same level after composting. Co-occurrence analysis of bacterial taxa and the genes suggested that the ARGs may spread via horizontal gene transfer during composting. In summary, even though aerobic composting is effective for managing sewage sludge and to decrease the relative abundance of potential pathogens, ARGs and HMRGs, it might include a potential risk for the dissemination of ARGs in the environment.

Co-composting of cattle manure and wheat straw covered with a semipermeable membrane: organic matter humification and bacterial community succession

Semipermeable membrane-covered composting is one of the most commonly used composting technologies in northeast China, but its humification process is not yet well understood. This study employed a semipermeable membrane-covered composting system to detect the organic matter humification and bacterial community evolution patterns over the course of agricultural waste composting. Variations in physicochemical properties, humus composition, and bacterial communities were studied. The results suggested that membrane covering improved humic acid (HA) content and degree of polymerization (DP) by 9.28% and 21.57%, respectively. Bacterial analysis indicated that membrane covering reduced bacterial richness and increased bacterial diversity. Membrane covering mainly affected the bacterial community structure during thermophilic period of composting. RDA analysis revealed that membrane covering may affect the bacterial community by altering the physicochemical properties such as moisture content. Correlation analysis showed that membrane covering activated the dominant genera Saccharomonospora and Planktosalinus to participate in the formation of HS and HA in composting, thus promoting HS formation and its structural complexity. Membrane covering significantly reduced microbial metabolism during the cooling phase of composting.

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.

Coupling network of hydrogen sulfide precursors and bacteria in kitchen waste composting

This study was focused on the changes of hydrogen sulfide (H₂S), its precursors, and microorganisms associated with its transformation during the composting process of kitchen waste. The results showed that the content of cysteine (Cys) and methionine (Met) decreased by 32.3 % and 57.5 % respectively, while the content of sulfate (SO₄^2-) changed little during composting. The main release period of H₂S was during the high-temperature period of composting, Cys was its main precursor. Based on network analysis, a total of 15 core genera associated with the conversion of H₂S precursors were identified, and the transformation of the H₂S precursor was mainly influenced by Filomicrobium. Temperature, pH, and TN levels had a positive effect on Filomicrobium. It could find a balance point by controlling these three factors to reduce the production of H₂S.

Insights into leachate reduction in landfill with different ventilation Rates: Balance of Water, waste physicochemical Properties, and microbial community

Ventilation is an efficient approach employed for accelerating stabilization and reducing aftercare of landfill, but its effect on leachate reduction is still elusive. To fill this knowledge gap, five lab-scale landfill reactors with different ventilation rates were established in this study. Suitable ventilation (e.g. 0.25-0.5 L·min^-1·kg^-1 dry solid of waste (DS)) was beneficial to promoting the stabilization of landfill, which effectively accelerated the degradation of organic matter and reduced water content of landfilled waste. Based on the mass balance of water, the dominant input water was initial water of landfilled waste (more than 94 %), which was partially converted to leachate and evaporated water. Ventilation enhanced the intensity of biochemical reactions heat to increase evaporated water content from 0 to 0.29 t/t DS while reducing the leachate generation significantly from 0.69 to 0.49 t/t DS with the increase of ventilation rate. Besides, the hydrophilic substances, such as humic acid-like substances, in landfilled waste increased, and the surface of the landfilled waste converted from smooth to rough. The reduction of the bound water content has a significant correlation with the degradation of organic matter content (p less than 0.05), which reduced the water-holding capacity of waste. Actinobacteriota and Firmicutes were the key bacterial phyla in the degradation of organic matter to promote bio-heat and evaporation of water, thus reducing leachate production under suitable ventilation conditions. Carbohydrates and amino acids were the main energy metabolism sources of bacteria during the landfill process. This study deepens our understanding of the leachate reduction mechanism in the micro-aerobic landfill.

Evaluation of physicochemical properties, bacterial community, and product fertility during rice straw composting supplemented with different nitrogen-rich wastes

This study evaluated the compostability of rice straw as the main feedstock (75 % in dry weight), supplemented with three different nitrogen-rich wastes, namely food waste (FW), dairy manure (DM), and sewage sludge (SS). Organic matter (OM) degradation, maturity and fertility of the end-product, and bacterial community structure during the composting processes were compared. All composting processes generated mature end-product within 51 days. Notably, FW addition was more effective to accelerate rice straw OM degradation and significantly improved end-product fertility with a high yield of Chinese cabbage. The succession of the bacterial community was accelerated with FW supplementation. Genera Geobacillus, Chryseolinea, and Blastocatella were significantly enriched during the composting of rice straw with FW supplementation. Finally, temperature, total nitrogen, moisture, pH, and total carbon were the key factors affecting microorganisms. This study provides a promising alternative method to enhance the disposal of larger amounts of rice straw in a shorter time.

Exploration of β-glucosidase-producing microorganisms community structure and key communities driving cellulose degradation during composting of pure corn straw by multi-interaction analysis

Poor management of crop residues leads to environmental pollution and composting is a sustainable practice for addressing the challenge. However, knowledge about composting with pure crop straw is still limited, which is a novel and feasible composting strategy. In this study, pure corn straw was in-situ composted for better management. Community structure of β-glucosidase-producing microorganisms during composting was deciphered using high-throughput sequencing. Results showed that the compost was mature with organic matter content of 37.83% and pH value of 7.36 and pure corn straw could be composted successfully. Cooling phase was major period for cellulose degradation with the highest β-glucosidase activity (476.25 μmol·p-Nitr/kg·dw·min) and microbial diversity (Shannon index, 3.63; Chao1 index, 500.81). Significant compositional succession was observed in the functional communities during composting with Streptomyces (14.32%), Trichoderma (13.85%) and Agromyces (11.68%) as dominant genera. β-Glucosidase-producing bacteria and fungi worked synergistically as a network to degrade cellulose with Streptomyces (0.3045**) as the key community revealed by multi-interaction analysis. Organic matter (-0.415***) and temperature (-0.327***) were key environmental parameters regulating cellulose degradation via influencing β-glucosidase-producing communities, and β-glucosidase played a key role in mediating this process. The above results indicated that responses of β-glucosidase-producing microorganisms to cellulose degradation were reflected at both network and individual levels and multi-interaction analysis could better explain the relationship between variables concerning composting cellulose degradation. The work is of significance for understanding cellulose degradation microbial communities and process during composting of pure corn straw.

Insight into the dynamic microbial community and core bacteria in composting from different sources by advanced bioinformatics methods

Microbial communities are important for high composting efficiency and good quality composts. This study was conducted to compare the changes of physicochemical and bacterial characteristics in composting from different raw materials, including chicken manure (CM), duck manure (DM), sheep manure (SM), food waste (FW), and vegetable waste (VW). The role and interactions of core bacteria and their contribution to maturity in diverse composts were analyzed by advanced bioinformatics methods combined sequencing with co-occurrence network and structural equation modeling (SEM). Results indicated that there were obviously different bacterial composition and diversity in composting from diverse sources. FW had a low pH and different physiochemical characteristics compared to other composts but they all achieved similar maturity products. Redundancy analysis suggested total organic carbon, phosphorus, and temperature governed the composition of microbial species but key factors were different in diverse composts. Network analysis showed completely different interactions of core bacterial community from diverse composts but Thermobifida was the ubiquitous core bacteria in composting bacterial network. Sphaerobacter and Lactobacillus as core genus were presented in the starting mesophilic and thermophilic phases of composting from manure (CM, DM, SM) and municipal solid waste (FW, VW), respectively. SEM indicated core bacteria had the positive, direct, and the biggest (> 80%) effects on composting maturity. Therefore, this study presents theoretical basis to identify and enhance the core bacteria for improving full-scale composting efficiency facing more and more organic wastes.

Effect of hydrothermal pretreatment and compound microbial agents on compost maturity and gaseous emissions during aerobic composting of kitchen waste

Though aerobic composting is commonly used in kitchen waste (KW) disposal, the high-oil and high-salt characteristics of KW could affect composting efficiency and lead to the land using risk of produced fertilizer. The impact of hydrothermal pretreatment (HTP) and addition of compound microbial agent (CMA) on compost maturity, greenhouse gas (GHGs) emissions and bacterial community during the kitchen waste composting were evaluated in the present work. Results indicated that N2O, CH4 and CO2 emissions from treatment by HTP and CMA addition were reduced by 82.72%, 13.77% and 20.78 %, respectively, comparing with the control (without HTP and without CMA addition). The seed germination index (GI) value of the HTP and CMA addition treatment was 1.03 and had the highest maturity in all treatments. Furthermore, the bacterial community analysis indicated that CMA inoculation could increase the relative abundance of genus Bacillus at the thermophilic stage of composting to accelerate organic biodegradation. This work provided important insight into mitigating GHGs emissions and improving compost quality in kitchen waste composting.

Effects of different microbial agents on bedding treatment of ectopic fermentation of buffalo manure

Introduction

The rapid development of the farming industry has increased the amount of manure produced by livestock and poultry, causing increasingly prominent environmental pollution problems. In recent years, due to the increase in conventional bedding material costs, an increasing number of farmers choose to use harmless recycled manure as bedding. Manure bedding treatment of farms can not only solve the problem of manure pollution, but also resource utilization of manure and cost savings.

Methods

This study compared the effects of five microbial agents (Microbial agents A, B, C, E, F) on buffalo manure bedding treatment by testing the temperature, moisture content, pH, microbial bacteria distribution of buffalo manure ectopic fermentation, and screened the lowest cost and most effective agent. The changes of microbial bacteria distribution in different periods of bedding treatment were also detected.

Results

Agent A was eliminated because of poor fermentation effect and low fermentation temperature, which could not achieve the effect of harmless treatment. The other four agents of bacteria achieved a harmless effect, but the bedding treatment effect of agent F was significantly better than agent E, B, and C. In terms of the cost of agents: the cost of agent F required for fermenting 100m^³ buffalo manure was the lowest, 1000yuan, followed by E (1200yuan), C (1750yuan), and B (1980yuan). In the process of ectopic fermentation bedding treatment of buffalo manure, Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Chloroflexi were the major bacteria used. The process was divided into three periods; the heating period - high temperature period - cooling period, the high temperature period could reach more than 75°C, and a large number of pathogenic bacteria and harmful bacteria, and other miscellaneous bacteria in the pile were degraded, their species diversity was reduced, and the structure of bacterial flora had significant differences in different treatment periods. In conclusion, this study has provided a guide for the resource utilization of manure in cattle farms and the reduction of manure pollution to the environment.

Dynamic changes of microbial community and moisture ratio during bio-drying of sludge after electro-dewatering

Using electro-dewatering as the pretreatment process for sludge bio-drying can improve the dewatering performance. It was innovatively investigated including the microbial mechanism and the kinetics of moisture removal by bio-drying with electro-dewatered sludge in this study. Two bio-drying processes using electro-dewatered sludge (EDS) and sludge added cornstalk conditioner (CSS) were compared. Microbial community analysis showed that the abundance of Bacteroidetes increased from 4.21% to 16.67% after electro-dewatering. The dominant phyla were Bacteroidetes (36.79%), Proteobacteria (32.35%), and Actinobacteria (24.58%) at the end of EDS bio-drying. Network analysis revealed that the co-occurrence patterns in EDS included 40 nodes and 97 edges. The prediction results of the Kyoto Encyclopedia of Genes and Genomes demonstrated that the relative abundances of carbohydrate metabolism and metabolism of terpenoids and polyketides in sludge decreased, while the relative abundances of lipid metabolism, xenobiotic biodegradation and metabolism increased after electro-dewatering. Five thin layer drying kinetic models were analyzed to estimate the bio-drying kinetic parameters. The Page's model could be better fitted to the results and the highest R² was 0.9570 in the EDS. The new coefficients k (0.1637) and n (1.2097) were obtained. The results provided mechanism and data support for exploring and applying bio-drying technology after sludge electro-dewatering.

Impacts of composting duration on physicochemical properties and microbial communities during short-term composting for the substrate for oyster mushrooms

A short-term composting process to prepare substrate is an effective way to cultivate oyster mushrooms (Pleurotus spp.), which can increase the yield of mushrooms and lower the rate of contamination in non-industrialized cultivation. Moreover, it is different from the traditional composting processes for fertilizers and lacks systematic study, such as microbial succession and compost quality. In this study, a series of different tests of composting duration (0, 2, 4 and 5 d) were performed. A composting duration of 4-5 d over 58 °C was suitable for mushroom cultivation based on the biological efficiency (BE) range of 69.76-73.41 % and the contamination rate of 0 %. The content of total carbon (TC) continuously decreased during composting, while the content of total nitrogen (TN) reacted in an opposite matter. The final TN and C/N ratios were 1.89 % and 28/1, respectively, which fell well within the optimal range of nutritional requirements for oyster mushroom cultivation. The composting bacteria were more diverse than the fungal species. Caldibacillus, Thermobispora, Thermopolyspora, Thermobacillus and Ureibacillus were the predominant bacterial genera during the thermophilic stage. Co-occurrence patterns of microbial communities and physicochemical properties were performed using a network analysis, which indicated that bacteria can play more efficient roles than fungi in the degradation of organic matter. The structural equation model showed that composting duration significantly affected bacterial diversity, lignocellulose degradation rates, and BE. The correlations between bioinformatics parameters with composting characters and agronomic traits were determined by the Mantel test and showed that the induction of bacterial diversity over time rapidly activated carbon metabolism during short-term composting. This study provides a new idea of agro-waste composting for mushroom cultivation.

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.

Thermophilic semi-continuous composting of kitchen waste: Performance evaluation and microbial community characteristics

This study evaluated the feasibility, system stability, and microbial community succession of thermophilic semi-continuous composting of kitchen waste (KW). The results revealed that treatment performance was stable at a 10 % feeding ratio, with an organic matter (OM) degradation efficiency of 81.5 % and seed germination index (GI) of 50.0 %. Moreover, the OM degradation efficiency and GI were improved to 83.4 % and 70.0 %, respectively, by maintaining an optimal compost moisture content (50-60 %). However, feeding ratios of ≥ 20 % caused deterioration of the composter system owing to OM overloading. Microbial community analysis revealed that Firmicutes, Actinobacteria, Chloroflexi, Proteobacteria, and Gemmatimonadetes were dominant. Additionally, moisture regulation significantly increased the Proteobacteria abundance by 57.1 % and reduced the Actinobacteria abundance by 57.8 %. Moreover, network analysis indicated that the bacterial community stability and positive interactions between genera were enhanced by moisture regulation. This information provides a useful reference for practical KW composting treatment in the semi-continuous mode.

Metagenomic analysis reveals the microbial degradation mechanism during kitchen waste biodrying

Biodrying is a treatment to remove moisture using bio-heat generated during organic degradation. Organic matter degradation and microbial metabolism were studied during the whole kitchen waste biodrying, using metagenomic analysis. After the 25-day biodrying process, carbohydrate, protein and lipid contents decreased by 83.7%, 27.8% and 79.3%, respectively, and their degradation efficiencies increased after the thermophilic phase. Lipase activity exceeded 10 mmol d^-1 g^-1 throughout biodrying. Cellulase and lipase activities recovered by 2.21% and 5.77%, respectively, after the thermophilic phase, while the protease activity had a maximum increment of 347%. Metabolic analysis revealed that carbohydrate, amino acid and lipid metabolism was possibly inhibited by the high temperature, but the relative abundances of related predicted functions recovered by more than 0.9%, 7% and 11%, respectively, by the end of biodrying. Protein function prediction suggests that β-oxidation, fatty acid biosynthesis, and the degradation of cellulose and chitin were possibly enhanced during the thermophilic phase. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that leucine, isoleucine and lysine could ultimately degraded to acetyl-CoA. Weissella, Aeribacillus and Bacillus were the genera with the most enriched functional genes during the whole biodrying process. These findings help elucidate the microbial degradation processes during biodrying, which provides further scientific support for improving the application of biodrying products.

Variation in community structure and network characteristics of spent mushroom substrate (SMS) compost microbiota driven by time and environmental conditions

Global mushroom production is growing rapidly, raising concerns about polluting effects of spent mushroom substrate (SMS) and interest in uses in composts. In this study, SMS composting trials and high-throughput sequencing were carried out to investigate to better understand how the structure, co-occurrence patterns, and functioning of bacterial and fungal communities vary through compost time and across environmental conditions. The results suggested that both bacterial and fungal microbiota displayed significant variation in community composition across different composting stages. Enzyme activity levels showed both directional and fluctuating changes during composting, and the activity dynamics of carboxymethyl cellulase, polyphenol oxidase, laccase, and catalase correlated significantly with the succession of microbial community composition. The co-occurrence networks are "small-world" and modularized and the topological properties of each subnetwork were significantly influenced by the environmental factors. Finally, seed germination and seedling experiments were performed to verify the biosafety and effectiveness of the final composting products.

Exploring the dynamic of microbial community and metabolic function in food waste composting amended with traditional Chinese medicine residues

The aim of this study was to explore the dynamic of microbial community and metabolic function in food waste composting amended with traditional Chinese medicine residues (TCMRs). Results suggested that TCMRs addition at up to 10% leads to a higher peak temperature (60.5 °C), germination index (GI) value (119.26%), and a greater reduction in total organic carbon (TOC) content (8.08%). 10% TCMRs significantly induced the fluctuation of bacterial community composition, as well as the fungal community in the thermophilic phase. The addition of 10% TCMRs enhanced the abundance of bacterial genera such as Acetobacter, Bacillus, and Brevundimonas, as well as fungal genera such as Chaetomium, Thermascus, and Coprinopsis, which accelerated lignocellulose degradation and humification degree. Conversely, the growth of Lactobacillus and Pseudomonas was inhibited by 10% TCMRs to weaken the acidic environment and reduce nitrogen loss. Metabolic function analysis revealed that 10% TCMRs promoted the metabolism of carbohydrate and amino acid, especially citrate cycle, glycolysis/gluconeogenesis, and cysteine and methionine metabolism. Redundancy analysis showed that the carbon to nitrogen (C/N) ratio was the most significant environmental factor influencing the dynamic of bacterial and fungal communities.

Static composting of cow manure and corn stalk covered with a membrane in cold regions

The disposal of livestock wastes is an urgent task in China. Compost is highly regarded for its ability to treat livestock wastes and protect arable land. In particular, some problems of livestock manure in cold regions, such as low efficiency because of low environmental temperature in winter, urgently need to be solved. In order to provide valuable composting information in the cold area at low environmental temperatures, the composting experiments were carried out with cow manure and corn stalk as substrates. The properties and bacterial community of compost samples in different stages were investigated. The electrical conductivity (EC), total nitrogen (TN), total phosphorus (TP), and organic matter (OM) of the final compost were 551 μS/cm, 1.12, 0.77, and 63.5%, respectively. No E. coli or Ascaris eggs were detected. The temperature was the key factor to affect the physical-co-chemical and biological properties. The absolutely dominant genera were Sporosarcina, Virgibacillus, Flavobacterium, and Steroidobacter in heating, high temperature, cooling, and maturing stages, respectively. Also, these bacteria could act as biological indicators during the composting process. Cryobacterium, Caldicoprobacter, Virgibacillus, and Sporosarcina were relatively novel genera in the compost piles in a cold environment. The biodegradation of exogenous substances mainly occurs in the initial and maturing stages. It is proven that composting can be carried out successfully in early spring or later autumn after a harvest.

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.

Aerobic composting of chicken manure with amoxicillin: Alpha diversity is closely related to lipid metabolism, and two-component systems mediating their relationship

Composting is a technology that can use various functional microorganisms to degrade antibiotics. However, antibiotics will cause a coercion for the growth of most microorganisms. Microorganism can survive different environments, thanks to the development of different adaptive responses. Often, two-component systems sense changes in the environment and trigger a cellular response and adaptation. Therefore, the main purpose of this study was to explore how the two-component system modulates the corresponding metabolic functions to affect alpha diversity during composting. The results show that amoxicillin increases species diversity, reduces species richness. Lipid metabolism is an important metabolic pathway mediating changes in alpha diversity. Two-component system indirectly affects alpha diversity by regulating lipid metabolism. Firmicutes are important microbial communities mediating changes in alpha diversity This work presents an understanding of the impact of environmental information processing on microbial diversity, during composting.

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.

Interaction and spatio-taxonomic patterns of the soil microbiome around oil production wells impacted by petroleum hydrocarbons

Numerous onshore oil production wells currently exist, and the petroleum hydrocarbon contamination of the surrounding soil caused by oil production wells is not well understood. Moreover, the impact of the distribution of the total petroleum hydrocarbons (TPH) in the soil on the microbiota requires further investigation. Accordingly, in this study, the distribution of petroleum hydrocarbons in the soils around oil production wells was investigated, and their alteration of the microbiota was revealed. The results revealed that in the horizontal direction, the heavily TPH-contaminated soils were mainly distributed within a circle with a radius of 200 cm centered on the oil production well; and in the vertical direction, the heavily TPH-contaminated soils were distributed within the 0-50 cm soil layer. A significant positive correlation was found between the microbial abundance and the TPH concentration in the soil with relatively low total carbon contents. Heavy TPH contamination (TPH concentration of >3000 mg/kg) significantly reduced the microbial diversity and altered the microbiota compared with the light TPH contamination (TPH concentration of around 1000 mg/kg). In the heavily TPH-contaminated soils, the relative abundances of the Proteobacteria and Bacteroides increased significantly; the network complexity among the soil microorganisms decreased; and the co-occurrence patterns were altered. In summary, the results of this study have reference value in the remediation of soils around oil production wells and provide guidance for the construction of microbial remediation systems for petroleum contamination.

Succession of the Bacterial Communities and Functional Characteristics in Sheep Manure Composting

Bacterial community is a key factor affecting aerobic composting, and understanding bacterial community succession is important to revealing the mechanism of organic matter degradation. In this study, the succession and metabolic characteristics of bacterial communities were explored in 45 days composting of sheep manure and wheat straw by using high-throughput sequencing technology and bioinformatics tools, respectively. Results showed that the alpha diversity of bacterial community significantly decreased in the thermophilic (T2) phase and then recovered gradually in the bio-oxidative (T3) and the maturation (T4) phases. Bacterial communities varied at different stages, but there were 158 genera in common bacterial species. Unclassified_f_Bacillaceae, Oceanobacillus, Bacillus, Pseudogracilibacillus, and Nocardiopsis were identified as keystone bacterial genera. Eleven genera were significantly correlated (p < 0.05), or even extremely significantly correlated (p < 0.001), with the physicochemical factors. Redundancy analysis (RDA) showed that changes of bacterial community diversity correlated with physicochemical factors. The highest relative abundances were amino acid and carbohydrate metabolism among the metabolic groups in the compost. These results will provide theoretical support for further optimizing sheep manure composting conditions and improving the quality of organic fertilizers.

Potential of biochar integrated manganese sulfate for promoting pig manure compost humification and its biological mechanism

This study aimed to clarify the effect of the integrated addition of different proportions of biochar (0 and 5%) and MnSO₄ (0, 0.25%, and 0.50%) to pig manure compost. The results indicated the integrated use of biochar (BC) and Mn²⁺ advanced the compost humification. In particular, the integrated use of 0.50% Mn²⁺ and 5% BC showed higher total organic carbon degradation (20.67%) and humic acid production (81.26 g kg^-1) than other treatments. Microbial community analysis showed the integrated use of BC and Mn²⁺ regulated the diversity and community structure of organic matter-mineralizing microbes by maintaining the relative abundance of bacteria Firmicutes (54.62%) and Proteobacteria (38.05%) at high levels during the thermophilic period and boosting those of the fungi of Ascomycota (58.91%) and Actinobacteria (15.60%) during the maturity period of composting. This study illustrated the potential and biological mechanisms of integrating BC and Mn²⁺ as additives in compost humification.

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.

Microbial composition and nitrogen removal pathways in a novel sequencing batch reactor integrated with semi-fixed biofilm carrier: evidence from a pilot study for low- and high-strength sewage treatment

The sequencing batch reactor (SBR) activated sludge process is a well-established technology for sewage treatment. One of the drawbacks of SBRs, however, total nitrogen (TN) removals is insufficient. By means of introducing four improvements, including semi-fixed biofilm carrier, sludge elevation mixing and change for the mode of influent and effluent, compliant standard for TN discharge was obtained in this novel SBR configuration during low- and high-strength sewage load. To illustrate the microbial compositions and functions of the attached biofilm on semi-fixed carrier and the suspended aggregates, as well as the nitrogen removal pathway, high throughput 16S rRNA gene amplicon sequencing, PICRUSt2 algorithm, and KEGG database were applied. The results revealed that (i) the microbial communities from suspended aggregates and biofilm samples were significantly different from each other; (ii) during low-strength sewage loads, TN removal was mainly by nitrification-denitrification. The suspended aggregates was responsible for denitrification, while the biofilm was focused on ammonium oxidation; (iii) during high-strength sewage loads, function of nitrate reductase from suspended aggregates was faded, and anammox and N assimilation by biofilm became dominant. Meanwhile, TN removal referring to the formation of L-glutamine via assimilation was the main pathway.

Succession of endophytic bacterial community and its contribution to cinnamon oil production during cinnamon shade-drying process

•

Shade-drying of cinnamon leaves makes great contribution to cinnamon oil production.

•

Shade-drying process changed the composition of endophytic bacterial community in cinnamon leaves.

•

The production of cinnamon oil and the evolution of endophytic bacterial community were positive correlated.

•

Saccharopolyspora has application potential on the improvement of cinnamon oil content.

Cinnamon oil is a blend of secondary metabolites and is widely used as spice. Endophytic bacteria are always related to the secondary metabolites production. However, the potential of endophytic bacteria communities for cinnamon oil production during cinnamon shade-drying process is still not clear. In this study, we investigated the composition and metabolic function of endophytic bacterial community during 80-day shade-drying process. The temporal dynamics of essential oil content and its dominant constituents were analyzed. The succession of endophytic bacterial community from d0 to d80 was identified. The influence of endophytic bacterial community evolution on cinnamon oil is significant positive. Predictive functional analysis indicated that shade-drying process was rich in Saccharopolyspora that produce enzymes for the conversion of phenylalanine to cinnamaldehyde. These findings enhance our understanding of the functional bacterial genera and functional genes involved in the production of cinnamon oil during cinnamon shade-drying process.

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.

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.

Plant-scale hyperthermophilic composting of sewage sludge shifts bacterial community and promotes the removal of organic pollutants

The dissipation of toxic organic pollutants during plant-scale hyperthermophilic composting and the influence of microbial community remain unclear. The results of plant-scale hyperthermophilic composting of municipal sludge with green waste showed that the residual concentrations of polyaromatic hydrocarbons, phthalates, polybrominated diphenyl ethers were <5 mg/kg and decreased over time, with the removal percentages from 12.1% to 51.2% during seven days of composting. High-throughput sequencingreveals that hyperthermophilic composting significantly reduced the diversity (e.g., observed species, chao1 and Shannon index) of bacterial community, shifting their structure and functions. The relative abundances of dominant phyla Proteobacteria and Firmicutes declined significantly, while those of extremophilic and heat-resisting phyla Deinococcus-Thermus and Chloroflexi increased dramatically. Some genera capable of degrading organic pollutants presented stably in sludge composts. Moreover, hyperthermophilic composting enriched the bacterial functions related to degradation and metabolism of cellulose and xenobiotics pollutants, which promoted the dissipation of organic pollutants and humification.