Compositional and functional succession of bacterial and fungal communities is associated with changes in abiotic properties during pig manure composting

Enhancement of microbial community dynamics and metabolism in compost through ammonifying cultures inoculation

The efficient use of livestock and poultry manure waste has become a global challenge, with microorganisms playing an important role. To investigate the impact of novel ammonifying microorganism cultures (NAMC) on microbial community dynamics and carbon and nitrogen metabolism, five treatments [5% (v/w) sterilized distilled water, Amm-1, Amm-2, Amm-3, and Amm-4] were applied to cow manure compost. Inoculation with NAMC improved the structure of bacterial and fungal communities, enriched the populations of the functional microorganisms, enhanced the role of specific microorganisms, and promoted the formation of tight modularity within the microbial network. Further functional predictions indicated a significant increase in both carbon metabolism (CMB) and nitrogen metabolism (NMB). During the thermophilic phase, inoculated NAMC treatments boosted carbon metabolism annotation by 10.55%-33.87% and nitrogen metabolism annotation by 26.69%-63.11. Structural equation modeling supported the NAMC-mediated enhancement of NMB and CMB. In conclusion, NAMC inoculation, particularly with Amm-4, enhanced the synergistic interaction between bacteria and fungi. This collaboration promoted enzymatic catabolic and synthetic processes, resultng in positive feedback loops with the endogenous microbial community. Understanding these mechanisms not only unravels how ammonifying microorganisms influence microbial communities but also paves the way for the development of the composting industry and global waste management practices.

Mitigation of ammonia and hydrogen sulfide emissions during aerobic composting of laying hen waste through NaOH-modified biochar

The impact of NaOH-modified biochar on the release of NH3 and H2S from laying hens' manure was examined for 44 days, using a small-scale simulated aerobic composting system. The findings revealed that the NaOH-modified biochar reduced NH3 and H2S emissions by 40.63% and 77.78%, respectively, compared to the control group. Moreover, the emissions of H2S were significantly lower than those of the unmodified biochar group (p < 0.05). The increased specific surface area and microporous structure of the biochar, as well as the higher content of alkaline and oxygenated functional groups, were found to facilitate the adsorption of NH3 and H2S. This enhanced adsorption capability was the primary reason for the significant reduction in NH3 emissions. Furthermore, during the high-temperature phase of composting, there was a notable alteration in the microbial community. The abundance of Limnochordaceae, Savagea, and IMCC26207 increased significantly which aided in the conversion of H2S to stable sulfate. These microorganisms also influenced the abundance of functional genes involved in sulfur metabolism, thereby inhibiting cysteine synthesis, along with the decomposition and conversion of sulfate to sulfite. This led to a significant decrease in H2S emissions. This study provides valuable data for the selection of deodorizers in the composting process of egg-laying hens. The results have significant implications for the application of NaOH-modified biochar for odor reduction in aerobic composting processes.

Effect of nitrogen retention composite additives Ca(H2PO4)2 and MgSO4 on the degradation of lignocellulose, compost maturation, and fungal communities in compost

This study investigated the effects of the nitrogen retention composite additives Ca(H2PO4)2 and MgSO4 on lignocellulose degradation, maturation, and fungal communities in composts. The study included control (C, without Ca(H2PO4)2 and MgSO4), 1% Ca(H2PO4)2 + 2% MgSO4 (CaPM1), 1.5% Ca(H2PO4)2 + 3% MgSO4 (CaPM2). The results showed that Ca(H2PO4)2 and MgSO4 enhanced the degradation of total organic carbon (TOC) and promoted the degradation of lignocellulose in compost, with CaPM2 showing the highest TOC and lignocellulose degradation. Changes in the three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) of dissolved organic matter (DOM) components in compost indicated that the treatment group with the addition of Ca(H2PO4)2 and MgSO4 promoted the production of humic acids (HAs) and increased the degree of compost decomposition, with CaPM2 demonstrating the highest degree of decomposition. The addition of Ca(H2PO4)2 and MgSO4 modified the composition of the fungal community. Ca(H2PO4)2 and MgSO4 increased the relative abundance of Ascomycota, decreased unclassified_Fungi, and Glomeromycota, and activated the fungal genera Thermomyces and Aspergillus, which can degrade lignin and cellulose during the thermophilic stage of composting. Ca(H2PO4)2 and MgSO4 also increased the abundance of Saprotroph, particularly undefined Saprotroph. In conclusion, the addition of Ca(H2PO4)2 and MgSO4 in composting activated fungal communities involved in lignocellulose degradation, promoted the degradation of lignocellulose, and enhanced the maturation degree of compost.

Effect of microbial inoculum on composting efficiency in the composting process of spent mushroom substrate and chicken manure

This work aimed to investigate the microbial mechanisms for the improvement of composting efficiency driven by the compound microbial inoculum (MI) (Bacillus subtilis SL-44, Enterobacter hormaechei Rs-189 and Trichoderma reesei) during co-composting of spent mushroom substrate (SMS) and chicken manure (CM). The treatments used in the study were as follows: 1) MI (inoculation with microbial inoculum), 2) CI (inoculation with commercial microbial inoculum), and 3) CK (without inoculation). The results demonstrated that MI increased the seed germination index (GI) by 25.11%, and contents of humus, humic acid (HA) and available phosphorus (AP) were correspondingly promoted by 12.47%, 25.93% and 37.16%, respectively. The inoculation of MI increased the temperature of the thermophilic stage by 3-7 °C and achieved a cellulose degradation rate of 52.87%. 16S rRNA gene analysis indicated that Actinobacteria (11.73-61.61%), Firmicutes (9.46-65.07%), Proteobacteria (2.86-32.17%) and Chloroflexi (0.51-10.92%) were the four major phyla during the inoculation composting. Bacterial metabolic functional analysis revealed that pathways involved in amino acid and glycan biosynthesis and metabolism were boosted in the thermophilic phase. There was a positive correlation between bacterial communities and temperature, humification and phosphorus fractions. The average dry weight, fresh weight and seedling root length in the seedling substrates adding MI compost were 1.13, 1.23 and 1.06 times higher than those of the CK, respectively. This study revealed that biological inoculation could improve the composting quality and efficiency, potentially benefiting the resource utilization of agricultural waste resources.

Malonic acid shapes bacterial community dynamics in compost to promote carbon sequestration and humic substance synthesis

The incorporation of malonic acid (MA) into compost as a regulator of the tricarboxylic acid (TCA) cycle has the potential to increase carbon sequestration. However, the influence of MA on the transformation of the microbial community during the composting process remains unclear. In this investigation, MA was introduced at different stages of chicken manure (CM) composting to characterize the bacterial community within the compost using high-throughput sequencing. We assess the extent of increased carbon sequestration by comparing the concentration of total organic carbon (TOC). At the same time, this study examines whether increased carbon sequestration contributes to humus formation, which was elucidated by evaluating the content and composition of humus. Our results show that the addition of MA significantly improved carbon sequestration within the compost, reducing the carbon loss rate (C loss (%)) from 64.70% to 52.94%, while increasing HS content and stability. High throughput sequencing and Random Forest (RF) analysis show that the introduction of MA leads to a reduction in the diversity of the bacterial communities, but enhanced the ability of bacterial communities to synthesize humus. Furthermore, the addition of MA favors the proliferation of Firmicutes. Also, the hub of operational taxonomic units (OTUs) within the community co-occurrence network shifts from Proteobacteria to Firmicutes. Remarkably, our study finds a significant decrease in negative correlations between bacteria, potentially mitigating substrate consumption due to negative interactions such as competition. This phenomenon contributes to the improved retention of TOC in the compost. This research provides new insights into the mechanisms by which MA regulates bacterial communities in compost, and provides a valuable theoretical basis for the adoption of this innovative composting strategy.

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.

Nutrient-cycling functional gene diversity mirrors phosphorus transformation during chicken manure composting

Elucidating ecological mechanism underlying phosphorus transformation mediated by phosphate-solubilizing bacteria (PSB) during manure composting is an important but rarely investigated subject. The research objective is to disentangle ecological functions of the inoculation of PSB Pseudomonas sp. WWJ-22 during chicken manure composting based on gene quantification and amplicon sequencing. There are large dynamic changes in phosphorus fractions, gene abundances, and bacterial community structure. The PSB addition notably increased available phosphorus from 0.29-0.89 g kg-1 to 0.49-1.39 g kg-1 and significantly affected phosphorus fractionation. The PSB inoculation significantly affected composition of nutrient-cycling functional genes (NCFGs), and notably influenced bacterial community composition and function. Compost bacteria showed significant phylogenetic signals in response to phosphorus fractions, and stochastic processes dominated bacterial community assembly. Results emphasized that PSB addition increased functional redundancy, phylogenetic conservatism, and stochasticity-dominated assembly of bacterial community. Overall, findings highlight NCFG diversity can be a bio-indicator to mirror phosphorus transformation.

Comparison of bacterial and fungal communities structure and dynamics during chicken manure and pig manure composting

Composting is a sustainable and eco-friendly technology that turns animal waste into organic fertilizers. It remains unclear whether differences exist in the structure of microbial communities during different livestock manure composting. This study analyzed the dynamic change of bacterial and fungal communities, metabolic function, and trophic mode during chicken manure (CM) and pig manure (PM) composting based on 16S rRNA and ITS sequencing. Environmental factors were investigated for their impact on microbial communities. During composting, bacterial diversity decreased and then increased, while fungal diversity slightly increased and then decreased. Saccharomonospora and Aspergillus were the dominant genera and key microorganisms in CM and PM, respectively, which played crucial roles in sustaining the stability of the ecological network structure in the microbial ecology and participating in metabolism. Saccharomonospora gradually increased, while Aspergillus increased at first and then decreased. PM had better microbial community stability and more keystone taxa than CM. In CM and PM, the primary function of bacterial communities was metabolism, while saprotroph was the primary trophic mode of fungal communities. Dissolved organic carbon (DOC) was the primary factor influencing the structure and function of microbial communities in CM and PM. In addition to DOC, pH and moisture were important factors affecting the fungal communities in CM and PM, respectively. These results show that the succession of bacteria and fungi in CM and PM proceeded in a similar pattern, but there are still some differences in the dominant genus and their responses to environmental factors.

Effects of fungal agents and biochar on odor emissions and microbial community dynamics during in-situ treatment of food waste

The effects of the co-addition of fungal agents and biochar on physicochemical properties, odor emissions, microbial community structure, and metabolic functions were investigated during the in-situ treatment of food waste. The combined addition of fungal agents and biochar decreased cumulative NH₃, H₂S, and VOCs emissions by 69.37%, 67.50%, and 52.02%, respectively. The predominant phyla throughout the process were Firmicutes, Actinobacteria, Cyanobacteria, and Proteobacteria. Combined treatment significantly impacted the conversion and release of nitrogen from the perspective of the variation of nitrogen content between different forms. FAPROTAX analysis revealed that the combined application of fungal agents and biochar could effectively inhibit nitrite ammonification and reduce the emission of odorous gases. This work aims to clarify the combined effect of fungal agents and biochar on odor emission and provide a theoretical basis for developing an environmentally friendly in-situ efficient biological deodorization (IEBD) technology.

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.

Biochar enhanced organic matter transformation during pig manure composting: Roles of the cellulase activity and fungal community

Fungal degradation of cellulose is a key step in the conversion of organic matter in composting. This study investigated the effects of adding 10% biochar (including, prepared from corn stalk and rape stalk corresponding to CSB and RSB) on organic matter transformation in composting and determined the role of cellulase and fungal communities in the conversion of organic matter. The results showed that biochar could enhance the conversion of organic matter, especially in RSB treatment. Biochar could increase cellulase activity, and RSB could enhance 33.78% and 30.70% the average activity of cellulase compared with the control and CSB treatments in the mesophilic to thermophilic phase, respectively. The results of high throughput sequencing demonstrated that Basidiomycota dominant in mesophilic phase, and Ascomycota dominant in other phases of composting. The redundancy analysis showed that Alternaria, Thermomycees, Aspergillus, Wallemia, and Melanocarpus might be the key fungi for the degradation of organic matter, and Fusarium, Penicillium, and Scopulariopsis may promote the conversion of organic matter. Network showed that the addition of RSB changed the interactions between fungal communities and organic matter transformation, and RSB treatment enriched members of Ascomycota related to organic matter transformation and cellulase activity. These results indicated that RSB improved organic matter conversion by enhancing the role of cellulase and fungal communities.

Plant growth stages covered the legacy effect of rotation systems on microbial community structure and function in wheat rhizosphere

Legume-based crop rotation is conducive to improve soil multifunctionality, but how the legacy effect of previous legumes influenced the rhizosphere  microbial community of the following crops along with growth stages remains unclear. Here, the wheat rhizosphere microbial community was assessed at the regreening and filling stages with four previous legumes (mungbean, adzuki bean, soybean, and peanut), as well as cereal maize as a control. The composition and structure of both bacterial and fungal communities varied dramatically between two growth stages. The differences in fungal community structure among rotation systems were observed at both the regreening and filling stages, while the difference in bacterial community structure among rotation systems was observed only at the filling stage. The complexity and centrality of the microbial network decreased along with crop growth stages. The species associations were strengthened in legume-based rotation systems than in cereal-based rotation system at the filling stage. The abundance of KEGG orthologs (KOs) associated with carbon, nitrogen, phosphorus, and sulfur metabolism of bacterial community decreased from the regreening stage to the filling stage. However, there was no difference in the abundance of KOs among rotation systems. Together, our results showed that plant growth stages had a stronger impact than the legacy effect of rotation systems in shaping the wheat rhizosphere microbial community, and the differences among rotation systems were more obvious at the late growth stage. Such compositional, structural, and functional changes may provide predictable consequences of crop growth and soil nutrient cycling.

Insight into the fate of metal ions in response to the refined classification and transformation order of dissolved organic matter components during municipal solid waste composting

The refined classification and subtle transformation order of dissolved organic matter (DOM) components may govern the fate of metal ions (MIs) during composting. However, the classification of DOM components is still rough and the fate of MIs in response to the refined transformation order of DOM during municipal solid waste composting (MSWC) has not been studied. Here, the refined classification and evolution order of DOM components were redefined by two-dimensional correlation spectroscopy (2DCOS) analysis. Eight DOM components were redefined and their evolution order was: tyrosine-like (peak B)>humic acid-like (peak C1>peak C2)>terrestrial humic-like with small molecular size (peak A)>UVA humic-like with medium molecular size (peak D2)>UVC humic-like with medium molecular size (peak D1)>UVA humic-like with large molecular size (peak E2)>UVC humic-like with large molecular size (peak E1). Na and As were releasing in the whole process of DOM transformation. Cu and Al showed strong affinity with humic-like fraction, the anabolism of which leading to storage of Cu and Al in compost. Si, Fe, Mn, Co, Zn, Ni, Sr, Mg and Cr tend to combine with humic-like fraction with small molecular size. These responses were influenced by synergistic effect of key microorganisms (two bacterial groups and three fungal groups), in which the contribution of bacteria was greater than fungus. Finally, partial least-square path models of "environmental factors-key microorganisms-transformation order of DOM-MIs" were constructed. The combination of humic-like fractions continuously produced during MSWC and MIs made compost product with potential environmental risks. It is of great significance to develop abiotic factors regulation approach based on refined classification and transformation of organic components for reducing environmental risks of compost product.

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.

Distinctive community assembly enhances the adaptation to extreme environments during hyperthermophilic composting

Hyperthermophilic composting (hTC) is a promising technique for solid waste treatment due to its distinctive microbiomes. However, the assembly process of the hTC microbial community remains unclear. We investigated the assembly process of hTC and explored the underlying drivers influencing community assembly in this work by employing conventional thermophilic composting (cTC) as a comparison group. Our results showed that the two composting treatments have different community assembly processes. Especially for the initial and thermophilic phases, hTC is affected by homogeneous dispersal (48%) and homogeneous selection (44%), respectively, while cTC is controlled by undominant (38%) and homogeneous selection (92%), respectively. Furthermore, random forest models and network results suggested that different factors govern the community assembly in these two composting methods. Specifically, the hTC community increases the stability of the thermophilic community via enhancing the interactions of low-abundance taxa with other operational taxonomic units (OTUs) in community assembly. Our results suggested that the distinctive nature of hTC community assembly may be responsible for its adaptation to extreme environments.

Evaluation of bacterial diversity in a swine manure composting system contaminated with veterinary antibiotics (VAs)

Composting has become an alternative for the treatment of organic effluents, due to its low cost, easy handling, and a great capacity for treating swine manure. As it is a biological process, many microorganisms are involved during the composting process and act in the degradation of organic matter and nutrients and also have the ability to degrade contaminants and accelerate the transformations during composting. The objective of this work was to identify microorganisms present in the swine effluent composting system, under the contamination by most used veterinary drugs in Brazil. The composting took place for 150 days, there was an addition of 200 L of manure (these 25 L initially contaminated with 17 antibiotics) in 25 kg of eucalyptus wood shavings. The microorganisms were measured at times (0 until 150 days) and were identified by the V3-V4 regions of the 16S rRNA for Bacteria, by means of next-generation sequencing (NSG). The results show seven different bacterial phyla (Proteobacteria, Bacteroidetes, Firmicutes, Acidobacteria, Actinobacteria, Spirochaetota and Tenericutes) and 70 bacterial genera (more than 1% significance), of which the most significant ones were Pseudomonas, Sphingobacterium, Devosia, Brucella, Flavisolibacter, Sphingomonas and Nitratireductor. The genus Brucella was found during mesophilic and thermophilic phases, and this genus has not yet been reported an in article involving composting process. With the results obtained, the potential for adaptation of the bacterial community was observed, being under the influence of antibiotics for veterinary use.

Dissolved organic matter evolution can reflect the maturity of compost: Insight into common composting technology and material composition

Dissolved organic matter (DOM) can clearly reflect composting components changes, thus it is supposed to indicate the humification process during composting. To demonstrate this, three compost mixtures and two techniques were arranged. DOM evolution was detected by three spectral techniques. X-ray diffraction (XRD) showed that the crystal structure substances decreased gradually during the composting, including cellulose, struvite, sylvine, quartz, and calcite; Specifically, the struvite was found, which was conducive to the fixation of nitrogen and phosphorus. Fourier transform infrared spectroscopy (FTIR) and three-dimensional fluorescence spectroscopy (3D-EEM) further showed that pig manure-based mixtures, added cabbage, and windrow composting are beneficial to sugar, protein, fulvic acid, and soluble microbial by-products decompose and humic acids produce. This process was closely related to the change of physical-chemical parameters (temperature; pH; moisture content; and NH₄⁺-N content) and maturity index (C/N ratio, E₄/E₆ and GI). Therefore, DOM evolution could quickly reflect the maturity process of compost. In subsequent research, the quantitative analysis of DOM components can be considered to modify DOM spectral parameters, or to build a model, so as to achieve rapid evaluation of compost maturity.

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.

Core fungal species strengthen microbial cooperation in a food-waste composting process

In ecosystem engineering research, the contribution of microbial cooperation to ecosystem function has been emphasized. Fungi are one of the predominant decomposers in composting, but thus far, less attention has been given to fungal than to bacterial cooperation. Therefore, network and cohesion analyses were combined to reveal the correlation between fungal cooperation and organic matter (OM) degradation in ten composting piles. Positive cohesion, reflecting the cooperation degree, was positively linked to the degradation rate of OM. From the community perspective, core species (i.e., Candida tropicalis, Issatchenkia orientails, Kazachstania exigua, and Dipodascus australiensis) with high occurrence frequency and abundance were the key in regulating positive cohesion. These species were highly relevant to functional genera associated with OM degradation in both fungal and bacterial domains. Therefore, focusing on these core fungal species might be an appropriate strategy for targeted regulation of functional microbes and promotion of degradation rates.

Effect of scleral protein shell amendment on bacterial community succession during the pig manure composting

The impact of scleral protein shell (SPS) amendment on bacterial community succession during pig manure (PM) composting were evaluated in the present work. Five treatments representing different dry weight dosage of SPS [0 % (T1), 2.5 % (T2), 5 % (T3), 7.5 % (T4), 10 % (T5) and 12 % (T6)] were applied with initial mixture of raw materials (Wheat straw along with the PM) and composted for 42 days. Results indicated that the dominant of phyla were Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes. The relative abundance (RA) of genus un-identified, Ruminofilibacter, Thermovum, Longispora and Pseudomonas were greater among the all treatments but interestingly genus Ruminofilibacter was also higher in control treatment. The network analysis was confirmed that T6 treatment with higher dosage of SPS amendment could enhance the bacterial population and rate of organic matter mineralization. Compared with T1, the T5 has greater potential impact to enhance the bacterial population and significant correlation among the pH and temperature.

Influence of different inoculation densities of black soldier fly larvae (Hermetia illucens) on heavy metal immobilization in swine manure

The disposal of organic waste by the biocomposting of black soldier fly larvae (BSFL) has drawn broad attention. However, the discrepancies in heavy metal immobilization between BSFL biocomposting with different inoculation densities and aerobic composting need to be further researched. In this study, BSFL with inoculation densities of 0.08%, 0.24% and 0.40% was added to swine manure to investigate its influence on heavy metal bioaccumulation and bioavailability. The physicochemical properties, BSFL growth performance and amino acid contents were measured. The results showed that the germination index, total prepupal yield and bioavailable fraction removal rate (%) of Cr and Pb at an inoculation density of 0.40% of BSFL were the highest among all of the BSFL biocomposting groups. Although the bioaccumulation factor and heavy metal (Cd, Cr, Cu and Zn) concentrations of the BSFL body from swine manure with inoculation densities of 0.24% and 0.40% of BSFL were similar, the BSFL inoculation density of 0.40% had the best absorption effect on these heavy metals in terms of total prepupal yield. Therefore, this study provides a basis for exploring the optimal inoculation density of BSFL biocomposting to reduce the harmful effects of heavy metals in swine manure.

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.

Antibiotic resistance genes and bacterial community distribution patterns in pig farms

Antibiotic-resistant pathogens pose high risks to human and animal health worldwide. In recent years, many studies have been carried out to investigate the role of gut microbiota as a pool of antibiotic resistance genes (ARGs) in human and animals. Both the structure and function of the gut bacterial community and related ARGs in pig remain unknown. In this study, we characterized the gut microbiomes and resistomes of fecal samples collected from sixteen pig farms located in sixteen cities of Shandong Province by metagenomic sequencing. Alpha diversity indicated that fecal samples from Dezhou (DZ) and Jinan (J) showed higher alpha diversity, and the lowest was from pig farms of Rizhao (RZ). Other pig farms showed similar alpha diversity. Besides, we found that the composition of gut bacterial among these pig farms varied greatly. Helcococcus massiliensis was the dominant bacterial species in pig farms of RZ and Zibo (ZB), while Prevotella sp. P5-92 occupied a superior proportion in Binzhou (BZ) and Yantai (YT). The proportion of Lactobacillus johnsonii was similar among farms of Qingdao (QD), Linyi (LY), Taian (TA), Weifang (WF), Weihai (WH), and YT. In total, 1112 ARGs were obtained and classified into 69 groups from 48 fecal samples. ARG abundance was higher in farms of Dongying (DY) and WH than others, while the lowest farms in BZ and ZB. Interestingly, it is found that BZ pig farm was exclusive, so the tetQ gene showed a higher abundance. In contrast, the load of APH(3') - IIIa in fecal samples from DY, J-1, LC, WF, and WH was high. Meanwhile, the most relevant ARGs and the corresponding microbes were screened out. Our metagenomic sequencing data provides new insights into the abundance, diversity, and structure of bacterial community in pig farms. Meanwhile, we screened ARG-carrying bacteria and explored the correlation between ARGs and bacterial community, which provide a comprehensive view of the pig fecial ARGs and microbes in different farms of Shandong.

Full-Scale of a Compost Process Using Swine Manure, Human Feces, and Rice Straw as Feedstock

Regarding the composting of rural waste, numerous studies either addressed the composting of a single waste component or were conducted at a laboratory/pilot scale. However, far less is known about the mixed composting effect of multi-component rural waste on a large scale. Here, we examined nutrient transformation, maturity degree of decomposition, and succession of microbial communities in large-scale (1,000 kg mixed waste) compost of multi-component wastes previously optimized by response models. The results showed that multi-component compost can achieve the requirement of maturity and exhibit a higher nutritional value in actual compost. It is worth noting that the mixed compost effectively removed pathogenic fungi, in which almost no pathogenic fungi were detected, and only two pathogenic bacteria regrown in the cooling and maturation stages. Structural equation models revealed that the maturity (germination index and the ratio of ammonium to nitrate) of the product was directly influenced by compost properties (electrical conductivity, pH, total organic carbon, moisture, temperature, and total nitrogen) compared with enzymes (cellulase, urease, and polyphenol oxidase) and microbial communities. Moreover, higher contents of total phosphorus, nitrate-nitrogen, and total potassium were conducive to improving compost maturity, whereas relatively lower values of moisture and pH were more advantageous. In addition, compost properties manifested a remarkable indirect effect on maturity by affecting the fungal community (Penicillium and Mycothermus). Collectively, this evidence implies that mixed compost of multi-component rural waste is feasible, and its efficacy can be applied in practical applications. This study provides a solution for the comprehensive treatment and utilization of rural waste.

Effects of thermophiles inoculation on the efficiency and maturity of rice straw composting

The present study investigated the effects of separately or simultaneously inoculating thermophilic fungus Aspergillus fumigatus Z5 and bacterium Geobacillus stearothermophilus B5 on lignocellulose degradation, enzyme activities and humification during rice straw composting. The results indicated that inoculation of Z5 accelerated the rise of temperature in the mesophilic phase, and the degradation degree of cellulose and hemicellulose was increased by 25.3% and 20.7%, respectively, due to the higher activities of lignocellulolytic enzymes. Inoculation of B5 increased 5-7 °C of the compost temperature in the thermophilic phase, and also prolonged the duration from 33 to 41 days. Inoculated simultaneously, the secreted hydrolases of Z5 generated more nutrition and promoted the growth of B5. B5 maintained and increased the compost temperature, thus presenting a better hydrolysis environment for extracellular hydrolases. Thermophilic inoculation altered the main physicochemical factors and improved efficiency and maturity in rice straw composting.

Biochar regulates bacterial-fungal diversity and associated enzymatic activity during sheep manure composting

Aimed to evaluate the coexistence of bacterial and fungal diversity and their correlation with enzymatic activity in response to biochar. This study performed aerobic composting based on typical agricultural wastes of sheep manure with additive apple tree branch biochar at distinct concentration (0, 2.5, 5, 7.5, 10 and 12.5% corresponding from T1 to T6). The result demonstrated that appropriate amendment of biochar enriched bacterial diversity (1646-1686 OTUs) but interestingly decreased fungal diversity (542-630 OTUs) compared to control (1444 and 682 OTUs). Biochar addition enhanced all enzymatic activities and its correlation with bacterial was more complex than fungal community (786 and 359 connect edges). The dominant microbes comprised of Firmicutes (45.2-35.2%), Proteobacteria (14.0-17.5%), Basidiomycota (32.4-49.5%) and Ascomycota (11.3-37.5%) among all the treatments. Overall, biochar regulates the composting microenvironment by influencing the microbial diversity and associated enzymatic activities.

Bacterial dynamics for gaseous emission and humification in bio-augmented composting of kitchen waste

Using high-throughput sequencing and Functional Annotation of Prokaryotic Taxa (FAPROTAX), this study aimed to elucidate the effect of bacterial dynamics on gaseous emission and humification of kitchen and garden wastes during composting augmented with microbial inoculants. Microbial inoculant addition at up to 0.9% resulted in a diverse bacterial community with more functional bacteria to amend gaseous emission and enhance humification. Microbial inoculation facilitated the enrichment of aerobic bacteria (e.g. the genus Bacillus and Thermobifida) to enhance cellulolysis and ligninolysis to advance organic humification. By contrast, several bacteria, such as the genus Weissella and Pusillimonas were inhibited by microbial inoculation to weaken fermentation and nitrate respiration. As such, bio-augmented composting with 0.9% microbial inoculant reduced the emission of methane by 11-20% and nitrogen oxide by 17-54%. On the other hand, ammonia and hydrogen sulphide emissions increased by 26-62% and 5-23%, respectively, in bio-augmented composting due to the considerable proliferation of the genus Bacillus and Desulfitibacter to enhance ammonification and sulphur-related respiration. Results from this study highlight the need to further develop efficient and multifunctional microbial inoculants that promote humification and deodorization for bio-augmented composting of kitchen waste as well as other carbon and nutrient rich organic wastes.