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Resistance genes have been identified as emerging pollutants due to their ability to rapidly spread in the environment through horizontal gene transfer (HGT). Microbial community serves as the pivotal factor influencing the frequency of HGT during manure composting. However, the characteristics of HGT in microbial community from different types of manure were unclear. Therefore, this study aimed to evaluate the potential risk of HGT in bacterial community through the co-composting of chicken manure and pig manure in different proportions. The experimental results showed that the abundance of sulfonamide antibiotic resistance genes and integrase genes was higher during pig manure composting than those during chicken manure composting. In addition, the addition of pig manure also increased resistance genes abundance during chicken manure composting. These results suggested that the potential HGT risk was greater during pig manure composting. Furthermore, microbial analysis of co-composting suggested that bacterial community of pig manure was more competitive and adaptable than that of chicken manure. Ultimately, statistical analysis indicated that compared to chicken manure composting, the potential ability of HGT was greater during pig manure composting. This study provided the vital theoretical support and scientific guidance for mitigating the HGT risk during manure composting. [Display omitted] • The pig manure addition increased sul3, zntA and intⅠ1 abundance in chicken manure. • The bacterial community of pig manure was more competitive and adaptable. • The potential genes spread risk was greater during pig manure composting. • The structure and response of bacterial community determined gene transfer ability. [ABSTRACT FROM AUTHOR]

Mobile genetic elements (MGEs) play critical roles in transferring antibiotic resistance genes (ARGs) among different microorganisms in the environment. This study aimed to explore the fate of MGEs during chicken manure (CM) and bovine manure (BM) composting to assess horizontal transfer risks of ARGs. The results showed that the removal efficiency of MGEs during CM composting was significantly higher than that during BM composting, because the potential host bacteria of MGEs were eliminated largely during CM composting. Meanwhile, these potential host bacterial communities are significantly influenced by pH, NH 4 +, NO 3 − and total N, which can be used to regulate host bacterial communities to remove MGEs during composting. Projection pursuit regression further confirmed that composting can effectively reduce the horizontal transfer risk of ARGs, especially for CM composting. These results identified the critical roles of host bacterial communities in MGEs removal during composting of different animal manures. Image 1 • The removal rate of MGEs was higher in CM composting than that in BM composting. • The potential host bacteria of MGEs were almost eliminated during CM composting. • The pH, NH 4 +, NO 3 − and total N can regulate MGEs removal during composting. • Fresh CM was confirmed to have greater risk for HGT in comparison with BM. Host bacterial community of MGEs determines the risk of horizontal gene transfer during composting of different animal manures. [ABSTRACT FROM AUTHOR]

This study was conducted to assess the abundance, incidence and diversity of the culturable phosphate-solubilizing bacteria (PSB) community during different organic wastes composting. The key PSB affecting different phosphorus (P) fractions and their relationship with environmental variables were analyzed by redundancy analysis (RDA). The results showed that there were distinct differences in amounts, incidence and community composition of PSB for the composts from different sources. Regression analysis demonstrated significant corrections between the density and incidence of PSB and pH, temperature, OM and DOC/DON. Most of culturable PSB showed high percentages of identity with the phyla of Firmicutes and Proteobacteria . There were thirteen key PSB correlated closely ( p < 0.05) with different P fractions variation. Conclusively, we suggested a process control method to regulate the distribution of P fractions during composting based on the relationship between the key PSB and P fractions as well as environmental parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Significant difference in nitrogen conversion of different composting. • Functional keystone involved in the nitrogen conversion were identified. • Change in abundance of functional keystone was limited during composting. • Composting microenvironment drove functional keystone. In this study, nitrogen transformation of chicken manure (CM) and cattle dung (CD) during composting was analyzed and its related functional keystones were identified. The results showed that chicken manure showed more severe nitrogen conversion during composting. The main N conversion factors in cattle dung were nitrite nitrogen (NO 2 –-N) and ammonium nitrogen (NH 4 +-N), while the main N conversion factors in chicken manure were NH 4 +-N and nitrate nitrogen (NO 3 –-N). The nitrogen-transforming bacterial community in chicken manure was more diverse. Variations in functional keystone abundances in cattle dung tended to be confined to the cooling and maturation periods, whereas changes in chicken manure persisted throughout the composting process. Environmental factors affected the functional keystones of nitrogen transformation. This study may provide directions for regulating nitrogen conversion in animal manure composting. [ABSTRACT FROM AUTHOR]

Heavy metal pollution was the main risk during livestock manures composting, in which microorganisms played a vital role. However, response strategies of microbial community to heavy metals stress (HMS) remained largely unclear. Therefore, the objective of this study was to reveal the ecological adaptation and counter-effect of bacterial community under HMS during chicken manures composting, and evaluating environmental implications of HMS on composting. The degradation of organic matters (more than 6.4%) and carbohydrate (more than 19.8%) were enhanced under intense HMS, suggesting that microorganisms could quickly adapt to the HMS to ensure smooth composting. Meanwhile, HMS increased keystone nodes and strengthened significant positive correlation relationships between genera (p < 0.05), indicating that bacteria resisted HMS through cooperating during composting. In addition, different bacterial groups performed various functions to cope with HMS. Specific bacterial groups responded to HMS, and certain groups regulated bacterial networks. Therefore, bacterial community had the extraordinary potential to deal with HMS and guarantee chicken manures composting even in the presence of high concentrations of heavy metals. [Display omitted] • Composting microorganisms could quickly adapt to heavy metals stress. • Microorganisms coped with heavy metals stress through cooperating. • Different bacterial groups performed various functions to cope with metals stress. • Chicken manures composting could be guaranteed even under intense metals stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen source supply affects humifaction process of rice straw composting. • HS and HA concentrations at 50 d of composting is higher in R_CM than that in R_UR. • Functional bacteria have specificity under driven by different nitrogen source. • Protein-like nitrogen source alleviate competition within bacterial community. • Chicken manure supply stimulates collaborative division of bacterial community. This study investigated effects of high-nitrogen source (urea) (R_UR) and protein-like nitrogen source (chicken manure) (R_CM) on humification process during lignocellulose biomass composting. It demonstrated that decreasing ratio of crude fiber (CF), polysaccharide (PS) and amino acids (AAs) in R_CM (29.75%, 53.93% and 73.73%, respectively) was higher than that in R_UR (14.73%, 28.74% and 51.92%, respectively). Humic substance (HS) concentration increased by 7.51% and 73.05% during R_UR and R_CM composting, respectively. The lower total links, more independent modularization and higher proportion of positive correlations between functional bacteria and organic components was observed with R_CM network than R_UR, indicating that protein-like nitrogen source supply may alleviate competition within bacterial community. Moreover, chicken manure supply favorably selects greater special functional bacterial taxa (Pusillimonas, Pedomicrobium, Romboustia and other 24 genus) related to AAs and stimulates the collaborative division of bacterial community. This is significance for strengthening effective transformation of organic components. [ABSTRACT FROM AUTHOR]

• Biochar and montmorillonite addition reduced the bioavailability of Cu and Zn. • Biochar and montmorillonite addition changed the bacterial community structure. • Biochar significantly enhanced the correlation between bacteria and HM fractions. • Bacterial community was a key factor in reducing bioavailability of HM. The aim of this study was to explore the effects of adding biochar and montmorillonite alone on the correlations between bacteria and bioavailability of heavy metals (HM) during chicken manure composting. Three composting experiments were conducted, containing the without ameliorant, 10% biochar and 10% montmorillonite. The results showed that biochar and montmorillonite ameliorants significantly reduced the bioavailability of Cu by 90.3%, 81.2%, while that of Zn by 11.7%, 15.6%, respectively. Meanwhile, they also significantly changed bacterial community structure and enhanced the correlation between bacterial bands (i.e., 19, 24, 26 and 30) and HM fractions. This correlation was validated in network analysis. Structural equation models further confirmed that bacteria had a complete and effective pathway to influence the bioavailability of HM. In summary, this study suggested that biochar and montmorillonite additions were an effective regulation method to reduce the bioavailability of HM from composting system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adenosine triphosphate and malonic acid slowed down organic carbon degradation. • The addition of regulators reduced carbon loss rate, which were 5.73% and 4.06%. • Carbon-related microbe composition varied significantly across treatments. • Functional microorganisms related to carbon metabolism were identified. • To identify TCA cycle regulation as a key factor in improving carbon content. As a kind of livestock manure, chicken manure (CM) was rich in organic matter and microorganisms. However, a large amount of foul gas discharged by its random stacking not only threatened the environment, but also caused harm to human health. In view of the serious carbon loss and the unclear action mechanism of microbial community on carbon metabolism during CM composting, the effect of adding regulators on the sequestration of organic carbon was explored. Therefore, the purpose of this study was to explore the regulation mechanism of adding tricarboxylic acid cycle (TCA cycle) regulators on the core carbon metabolism pathway during CM composting. The results showed that the adenosine triphosphate (ATP) and malonic acid (MA) slowed down organic carbon degradation, resulting in lower carbon loss rate, which were 64.99% (CK), 62.35% (MA), and 61.26% (ATP) in each treatment. By comparing the abundance and structure of the carbon-related bacterial communities in different treatments, it was found that adding ATP and MA not only reduced the bacterial community abundance, but also tended to be similar in bacterial community composition. Moreover, the microbial specificity related to carbon metabolism pathway was enhanced, while the related gene expression and gene abundance were weakened. The regulation of TCA cycle metabolism pathway was confirmed to be the main way to improve organic carbon content. These findings revealed the positive effects of ATP and MA on carbon fixation from the perspective of gene metabolism. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is one of the essential nutrient elements for plant growth and development. Sludge compost products can be used as an important source of soil P to solve the shortage of soil P. The difference in the initial carbon-to-phosphorus ratio (C/P) will lead to difference in the bacterial community, which would affect the biological pathway of P conversion in composting. However, few studies have been reported on adjusting the initial C/P of composting to explore P conversion. Therefore, this study investigated the response of P component transformations, bacterial community and P availability to C/P during sludge composting by adjusting initial C/P. The results showed that increasing C/P promoted the mineralization of organic P and significantly increased the content of the labile P. High C/P also increased the relative content of available P, especially when the C/P was at 45 and 60, it reached 60.51% and 60.47%. High C/P caused differences in the community structure, and improved the binding ability of microbial network modules and the competitiveness of microbial communities. Additionally, high C/P strengthened the effect of microbial communities on the transformation of P components. Finally, the study showed that C/P was the main contributor to P content variation (64.7%) and indirectly affected P component conversion by affecting the microbial community. Therefore, adjusting the C/P is crucial to improve the P utilization rate of composting products. [Display omitted] • High C/P ratio was conducive to the formation of LP and AP. • High C/P ratio could promote conversion of MLP, NLP and OP. • High C/P ratio enhanced the roles of core bacteria on the P transformation. • C/P indirectly affects bacterial community to regulate P transformation. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Malonic acid (MA) directionally shapes bacterial communities in compost. • MA facilitates the growth of Firmicutes in chicken manure compost. • MA addition simplifies bacterial communities to reduce carbon loss. • MA increases the importance of Firmicutes in bacterial interaction networks. • MA increases the efficiency of bacterial synthesis of humic substances. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Semi-continuous replacements of materials changes bio-heat generation distinctly. • Enzyme activity, temperature and bacterial community mainly affect heat generation. • Semi-continuous replacements of materials after inoculation benefits rapid heating. • A method for heat preservation in low-temperature composting is suggested. Abstract Development of cold-adapted microbial agent is an efficient approach for composting in low temperature. The study was conducted to evaluate the effect of semi-continuous replacements of compost materials after inoculation (SRMI) on the heat preservation of low temperature composting derived from chicken manure. Results revealed that SRMI could significantly improve the heat preservation of the pile, although the time of start-up in two inoculation groups was approximately the same. Due to the increase in the number of replacements of materials led to the changes in microbial community structures and enzyme activity. Non-metric multidimensional and colorimetric methods indicated that microbial community structures and enzyme activity was completely different in SRMI. Structural equation model was constructed by key factors involved in diversity of the microbial community, enzyme activity, temperature and bio-heat generation. In summary, SRMI decidedly increase the heat preservation time of the pile and start-up efficiency of the low temperature composting. [ABSTRACT FROM AUTHOR]

The mineralization of organic components releases CO 2 during composting, which not only leads to the loss of organic carbon, but has a direct negative impact on the environment. Malonic acid as a competitive inhibitor of succinate dehydrogenase could affect the tricarboxylic acid (TCA) cycle and reduce CO 2 emissions. However, the bacterial interaction and organic component transformation has less known how to malonic acid reduce CO 2 and improve of humus synthesis in complex composting. The aim of this study was to investigated the malonic acid on organic carbon sequestration and transforming cow manure waste into products with high humus content. Humus content was elevated by 16.8% and cumulative CO 2 emissions (30 d)d reduced by 13.6% after malonic acid addition compared to the CK. SparCC analysis of bacterial interaction presented that the network complexity and stability was more higher with malonic acid addition, while a greater concentration of keystones and their ecological metabolic functions was observed, suggesting they weaken the influence of TCA cycle inhibition by enhancing interactions. PICRUSt predictions indicate that malonic acid might enhance humus content by promoting the synthesis of polyphenols and polymerization with amino acids. This study investigated the potential mechanism of regulators to enhance quality and reduce emissions during humification process, providing a new strategy for the resource utilization of organic solid waste. [Display omitted] • Identified the role of malonic acid on CO 2 emission and humus formation. • Malonic acid inhibited TCA cycle and altered the bacteria community in composting. • Malonic acid strengthens the stability and complexity of co-occurrence network. • Malonic acid promoted humus formation mainly based on phenol-protein theory. [ABSTRACT FROM AUTHOR]

This study aimed to investigate different transformation mechanisms of organic nitrogen (N) fractions during composting with different raw materials, and the contributions of bacterial communities and environmental factors to organic N fractions transformation. The results showed that high molecular weight organic N was first degraded to low molecular weight organic N and then turned into NH 4 + during chicken manure composting. In comparison, organic N fractions were stored in composts rather than mineralization during garden waste and municipal solid waste composting. Meanwhile, bacterial communities, environmental factors and the combination of them were the main drivers of N transformation during chicken manure, municipal solid waste and garden waste composting, respectively. In conclusion, the proposed organic N transformation mechanisms in this study provided a theoretical basis for improving the quality of compost products. [ABSTRACT FROM AUTHOR]

Enriched phosphate-solubilizing bacteria (PSB) agent were acquired by domesticated cultivation, and inoculated into kitchen waste composting in different stages. The effect of different treatments on organic acids production, tricalcium phosphate (TCP) solubilization and their relationship with bacterial community were investigated during composting. Our results pointed out that inoculation affected pH, total acidity and the production of oxalic, lactic, citric, succinic, acetic and formic acids. We also found a strong advantage in the solubilization of TCP and phosphorus (P) availability for PSB inoculation especially in the cooling stage. Redundancy analysis and structural equation models demonstrated inoculation by different methods changed the correlation of the bacterial community composition with P fractions as well as organic acids, and strengthened the cooperative function related to P transformation among species during composting. Finally, we proposed a possible mechanism of P solubilization with enriched PSB inoculation, which was induced by bacterial community and organic acids production. [ABSTRACT FROM AUTHOR]

The aim of this work was to identify the factors which can affect humic substance (HS) formation. Composting periods, HS precursors, bacteria communities and environment factors were recognized as the key factors and few studies explored the potential relationships among them. During composting, HS precursors were mainly formed in the heating and thermophilic phases, but HS were polymerized in the cooling and mature phases. Moreover, bacterial species showed similar classification of community structure in the same composting period of different materials. Furthermore, structural equation model showed that NH 4 − -N and NO 3 − -N were the indirect environmental factors for regulating HS formation by the bacteria and precursors as the indirect and direct driver, respectively. Therefore, both environmental factors and HS precursors can be the regulating factors to promote HS formation. Given that, a new staging regulating method had been proposed to improve the amount of HS during different materials composting. [ABSTRACT FROM AUTHOR]

In order to put forward a method to promote composting start-up at low ambient temperature, the cold-adapted microbial agent (CAMA) was inoculated in chicken manure (CM), and compared the enzymes activities, including urease, proteases, β-glucosidase and invertase, with no CAMA group (CK). In this study, the temperature of CM reached 50 °C in 53 h, but it in CK was only around 30 °C during the composting process. Moreover, the enzymes exhibited higher activity in CM than CK, indicating the effectiveness of CAMA. Furthermore, redundancy analysis was conducted to study the relationships of CAMA, with enzymes activities and temperature. Results showed that the positive effect of CAMA on the enzyme activities were achieved by affecting the bacterial community structure. Accordingly, we provide a method to guide CAMA inoculation for promoting compost start-up in cold area. [ABSTRACT FROM AUTHOR]

The aim of this work was to put forward a method to improve HS amount by studying the formation regularity of HS. Five precursors have been detected and few researches combined them with bacteria to study HS formation. During composting, the polyphenols, carboxyl and amino acids concentration decreased by 75.8%, 63.2% and 68.3% on average, respectively. However, the polysaccharides, reducing sugars and HS concentration increased by 61.2%, 47.1% and 37.33% on average. Relationships between precursors and HS concentration showed that the HS formation were significantly affected ( p < 0.05). The key bacteria community and physical–chemical parameters which affected HS formation have also been identified by redundancy analysis. Twelve key bacteria communities have been selected, which were significantly affected by physical–chemical parameters ( p < 0.05). Accordingly, we proposed an adjusting method to promote HS amount during composting based on the relationship between the key bacteria communities and the precursors as well as physical–chemical parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calcium superphosphate addition reduced ammonia emissions and fixed NH 4 +-N content. • Addition of calcium superphosphate changed the species of the ammonifying bacteria. • Adding calcium superphosphate weakened the ammonification at high temperature. Nitrogen losses through ammonia (NH 3) emission were an unavoidable issue during chicken manure composting. Calcium superphosphate can be added to effectively limit the emission of NH 3. The results show that adding calcium superphosphate in the heating, high temperature and cooling stages reduces ammonia emission by 18.48 %, 28.19 % and 0.91 % respectively. Furthermore, adding calcium superphosphate at high temperature stage increased the ammonium nitrogen content (NH 4 +-N), reducing the conversion of organic nitrogen (HON) to NH 4 +-N. Network analysis indicated that adding calcium superphosphate during the high temperature stage reduced NH 3 -related microorganisms and effectively inhibited ammonification. Moreover, the results of qPCR of the ammonification gene gdh and structural equation model (SEM) verify that adding calcium superphosphate at the high temperature stage reduced ammonification and drove ammonification-related bacterial communities to decrease ammonia emissions. Adding superphosphate at high temperature can effectively increase the nitrogen content and reduce gas pollution during composting. [ABSTRACT FROM AUTHOR]

The study was conducted to investigate the influence of biochar and/or phosphate-solubilizing bacteria (PSB) inoculants on microbial biomass, bacterial community composition and phosphorus (P) fractions during kitchen waste composting amended with rock phosphate (RP). There were distinct differences in the physic-chemical parameters, the proportion of P fractions and bacterial diversity in different treatments. The contribution of available P fractions increased during composting especially in the treatment with the addition of PSB and biochar. Redundancy analysis showed that bacterial compositions were significantly influenced by P content, inoculation and biochar. Variance partitioning further showed that synergy of inoculated PSB and indigenous bacterial communities and the joint effect between biochar and bacteria explained the largest two proportion of the variation in P fractions. Therefore, the combined application of PSB and biochar to improve the inoculation effect and an optimized regulating method were suggested based on the distribution of P fractions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Elevated ammonium levels promote the formation of organic nitrogen. • High ammonium nitrogen reduces nitrogen losses during sludge composting. • Transformation of nitrogen fractions by the bacterial community was altered. • Core bacterial communities promoted the conversion of NH 4 +-N to AN and HUN. This study aimed to clarify the conversion relationship between organic and inorganic nitrogen. The NH 4 Cl was used to enhance the inorganic nitrogen content. The key role of bacterial conversion of ammonium to organic nitrogen under ammonium stress was explored. Studies had shown that ammonium stress increased the amide nitrogen and bioavailable nitrogen content by 36.95% and 32.25%, respectively. Network and regression analyses showed that the microbial community structure was restructured by high ammonium and more bacteria were involved in the conversion of inorganic nitrogen to organic nitrogen(i.e., amide nitrogen, unknown nitrogen). Variation partition analysis and structural equation model showed that the bacterial community was the main contributor to organic nitrogen production(up to 67.4%), which reduced the nitrogen loss by 6.03%. These findings shed light on the poorly understood interaction between inorganic and organic nitrogen by clarifying the role of core bacterial communities in nitrogen conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Exogenous amino acids promoted lignocellulose degradation and humus synthesis. • Amino acids promoted humus synthesis by acting as precursors. • Amino acids promoted humus synthesis by affecting bacterial communities. • Key bacteria involved in humus synthesis were identified. • The metabolic function of bacterial community was analyzed. This study was aimed at exploring the mechanism of promoting humus formation by the addition of exogenous amino acids. Amino acids not only participated in the synthesis of humus directly as precursors, but also changed the functions of bacterial communities. The composition and diversity of bacterial community changed with the addition of amino acids. The ability of bacterial community to degrade lignocellulose was enhanced, which provided precursors for humus synthesis. The key bacteria for humus formation and organic matter transformation were identified using random forests. These bacteria showed growth advantage with the addition of amino acids. The results showed that exogenous amino acids tended to transform organic matter and synthesize humus. Variance partitioning analysis confirmed that the bacterial community was the driving force of humus synthesis. These results were further verified by the structural equation model. These findings provided new ideas and understanding for straw waste composting. [ABSTRACT FROM AUTHOR]

[Display omitted] • MnO 2 improved the humification degree of FA components in composting. • Core bacteria associated with FA components transformation were identified. • Core bacteria could be divided into transforming and processing bacteria. • Transforming bacteria was a dominant factor in transfotmation of FA components. Here, we revealed the effects of microbes on fulvic acid (FA) formation in composting by adding MnO 2. The results showed that the MnO 2 promoted the formation of highly humified components (79.2% increased for component 2, and 45.8% increased for component 3) in FA. Additionally, core bacteria involved in FA transformation were identified, the MnO 2 increased the relative abundance of core bacteria. Notably, two different core bacteria types were identified: "transforming bacteria" and "processing bacteria". The "transforming bacteria" dominated (about 40% contribution) in the formation of FA components with a high humification degree. The structural equation model confirmed that "transforming bacteria" could convert partly FA components with low humification into highly humified components, and the "transforming bacteria" could be regulated by environmental factors. These findings provided a new insight to manage FA humification degree during composting and helped to improve the application value of FA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using life history strategy to evaluate microbe in rice straw compost. • Bacillus inoculation promotes lignocellulose degradation. • Bacillus inoculation affects indigenous microorganisms. • Indigenous bacterial with complex interrelationships have stability. • The bacteria with stronger degradation ability were affected by inoculation. Bacillus is the classic inoculant in rice straw composting. However, there has been no in-depth study of the mechanism promoting the degradation of lignocellulose and the change of indigenous bacterial communities after Bacillus inoculation. Moreover, the stability of bacterial communities is a significant challenge in achieving the efficacy of inoculation. In this study, the ecological succession and yield-resource acquisition-stress tolerance (Y-A-S) framework were combined with Redundancy analysis (RDA) and changes in relative abundance, Bacillus was found to be a pioneer bacterium that adopts a resource acquisition-stress tolerance strategy. The structural equation model (SEM) revealed that in addition to exerting a degradation effect, Bacillus inoculation could also indirectly affect lignocellulose degradation by changing the bacterial community. Random forest model and network analysis indicated a change in bacterial communities after inoculation, and bacteria with more complex relationships and weaker decomposition ability were key to the stability of bacterial communities. [ABSTRACT FROM AUTHOR]

• Composting humin with higher humification had better sorption of heavy metals. • Heavy metal resistant bacteria in composting could bind more metal ions than humin. • Biomass and humification are the key factors for the biosorption of heavy metals. • Humin improved heavy metals biosorption by affecting bacterial diversity and biomass. • Combining MPHM with heavy-metal resistant bacteria is fit for heavy metal removal. This study aims to assess the roles of different humin and heavy-metal resistant bacterial community from composting on heavy metal removal. The results showed that the concentration of Cu2+, Zn2+, Ni2+, Pb2+, Cr3+ and Cd2+ decreased with adding the compost-derived humin, but the removal rates were relatively low (<30% on average). The heavy metal resistant bacteria from composting have better metal binding capacities than humin, and the combined addition of humin and bacteria could further stimulate the biosorption of heavy metals with 60–80% removal of metals and improve the diversity and biomass of bacterial community. There was obviously increased synergy between the humin from maturity phase and bacteria for metal biosorption ("1 + 1 > 2"). Structural equation modeling showed that microbial biomass and humin humification are the key factors for the biosorption of heavy metals. Combining humin from maturity phase with heavy-metal resistant bacteria was suggested to control heavy metal pollution in composts. [ABSTRACT FROM AUTHOR]

• NH 3 recycling changes the contents of N fractions during sludge composting. • NH 3 recycling affects the relationship between N fraction and bacterial community. • SEM revealed the possible linkages among different N fractions. • A novel perspective was proposed to reduce N loss during composting. The aim of this study is to reduce nitrogen (N) loss and investigate the role of ammonia (NH 3) recycling on N fractions, environmental factors and bacterial communities. In this study, collected NH 3 from composting and recycled in it. The results showed that NH 3 recycling affected N-cycling processes such as nitrification. Redundancy Analyses (RDA) showed that NH 4 +-N had significantly negative correlation with denitrifying bacteria in treatment group (p < 0.05), demonstrating that NH 3 recycling have influenced on the bacterial community structure. Furthermore, Structural Equation Model (SEM) revealed causal relationships between visual variables. Based on these results, we concluded that NH 3 recycling is a novel method to reduce N loss. [ABSTRACT FROM AUTHOR]

• Minerals promoted the transformation of complex components to humic acid. • Humic acid production increased by 45.39% in composting by adding mixed minerals. • Identified the core bacterial communities associated with humic acid formation. • Established the multi-level model of minerals promoting HA formation. This work was aimed to determine the effects of different minerals on humic acid (HA) formation. Minerals can stimulate the formation of complex compounds, however, whether they can promote the conversion of complex compounds to HA has not been verified. Four treatments were setup from chicken manure mixed with rice hull and then added biochar (BC), montmorillonite (MMT) and biochar combined with montmorillonite (BC-MMT) for composting, while the control check (CK) was composted without minerals. The results showed that HA concentration was increased by 28.09%, 40.79%, 45.39% and 38.96% during CK, BC, BC-MMT and MMT composting. However, the bacterial community was the main reason for affecting HA concentration. Network analysis showed that obligate and facultative core microbes drove HA formation, and these driving effects were affected by minerals. Therefore, the core bacterial community promoted HA formation, which provided an insightful method to improve HA production. [ABSTRACT FROM AUTHOR]

• Different additives increased BON contents of composts in the order: BCM > M > BC. • Montmorillonite promoted N loss during CM composting. • BCM can not only increase BON contents, but also reduced N loss during composting. • Additives affected N transformation mediated by microorganisms during composting. This study aimed to compare the effects of biochar, montmorillonite and their mixture on nitrogen availability and nitrogen loss during chicken manure composting. Four lab-scale composting experiments, the control (CK), 5% biochar addition (BC), 5% montmorillonite addition (M) and 2.5% biochar + 2.5% montmorillonite addition (BCM), were established. Results showed that the addition of BC, M and BCM significantly improved the contents of bioavailable organic nitrogen and NH 4 +-N in composts. In addition, BC and BCM reduced N loss by 19.2% and 12.2%, respectively, in comparison with CK. Significant shift of key bacterial communities associated with N transformation were also found in four treatments. Redundancy analysis and structural equation models indicated different additives changed the correlation among bacterial communities, environmental factors and organic N fractions. Comparison of N availability and N loss indicated that the combination of biochar and montmorillonite are more effective than that of separate application during composting. [ABSTRACT FROM AUTHOR]

• Each neutral sugar is converted by a specific group of bacteria in RS composting. • A group of bacteria can convert multiple neutral sugars during MD and L composting. • The diversity of bacterial community lead to the difference in the conversion. • The GM/AX is found to characterize the neutral sugars conversion during composting. The aim of this study was to explore the conversion characteristics of neutral sugars during different lignocellulose wastes composting from rice straw (RS), leaf (L) and mushroom dreg (MD). The results showed that the changes of neutral sugars were different during different wastes composting, but the changes of various hexose or pentose were similar during composting of the same material. The diversity of bacterial community led to different conversion characteristics of neutral sugars. During RS composting, each neutral sugar was transformed by a specific group of bacteria. However, a group of bacteria could transform multiple neutral sugars during MD and L composting. Furthermore, GM/AX value was first applied to composting, which could be used to characterize the conversion of neutral sugars during composting. This will help to provide more efficient recommendations for lignocellulose wastes treatment and accelerating humic substances synthesis during composting. [ABSTRACT FROM AUTHOR]

• Compost plays a positive role in mitigating the bioavailability of heavy metals. • Organic matters and temperature are driving factors in beef cattle manures. • Physicochemical property and bacterial community are primary in chicken manures. • The bioavailability will be mitigated precisely according to deactivation pathways. The aim of this study was to explore the pathways to mitigate the bioavailability of heavy metals (HM) during chicken and beef cattle manures composting. For raw materials, HM contents in animal manures from breeding farm were 1.5–3 times as much as that of domestic animal manures. Structural equation models (SEMs) based on denaturing gradient gel electrophoresis (DGGE) showed that mitigating bioavailability of HM was mainly attributed to physicochemical properties (organic matters content and temperature) during beef cattle manures composting. However, both physicochemical properties (organic matters content, temperature, pH and moisture) and bacterial community were critical factors during chicken manures composting. Furthermore, the statistical analysis from high-throughput sequencing verified the results of SEMs. Therefore, the bioavailability of HM will be mitigated by different deactivation pathways according to diverse raw materials composting. [ABSTRACT FROM AUTHOR]

• Composting can increase the bioavailability of organic-N. • CM has more bacterial taxa related with bioavailable organic-N than MSW and GW. • High-molecular-weight BON were degraded into low-molecular-weight by core bacteria. • Moisture, C/N and pH can be used to regulate BON transformation during composting. This study aimed to explore the roles of bacterial community in the transformation of bioavailable organic-N (BON) during different wastes composting. BON fractions with different forms and molecular weights were identified in this study. Results indicated that core bacterial communities improved the availability of BON by degrading high molecular weights BON into low molecular weights BON during different wastes composting. A total of fifty-two core bacterial genera involved in BON transformation were identified by network analysis. Three types of high molecular weights BON fractions (amino acid-N, amine-N and amino sugar-N) were degraded by bacteria during chicken manure and garden waste composting, while only amine-N was degraded during municipal solid waste composting. Finally, moisture, C/N and pH were identified as the key operational parameters affecting BON transformation mediated by microorganisms, which can be used to improve bioavailability of organic-N and reduce N loss during composting. [ABSTRACT FROM AUTHOR]