Aerobic composting of chicken manure with penicillin G: Community classification and quorum sensing mediating its contribution to humification

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

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

Biochar improves the humification process during pig manure composting: Insights into roles of the bacterial community and metabolic functions

Biochar could promote humification in composting, nevertheless, its mechanism has not been fully explored from the perspective of the overall bacterial community and its metabolism. This study investigated the effects of bamboo charcoal (BC) and wheat straw biochar (WSB) on the humic acid (HA) and fulvic acid (FA) contents during pig manure composting. The results showed that BC enhanced humification more than WSB, and significantly increased the HA content and HA/FA ratio. The bacterial community structure under BC differed from those under the other treatments, and BC increased the abundance of bacteria associated with the transformation of organic matter compared with the other treatments. Furthermore, biochar enhanced the metabolism of carbohydrates and amino acids in the thermophilic and cooling phases, especially BC. Through Mantel tests and network analysis, we found that HA was mainly related to carbon source metabolism and the bacterial community, and BC might change the interaction patterns among carbohydrates, amino acid metabolism, Bacillales, Clostridiales, and Lactobacillales with HA and FA to improve the humification process during composting. These results are important for understanding the mechanisms associated with the effects of biochar on humification during composting.

Regulation of extracellular polymers based on quorum sensing in wastewater biological treatment from mechanisms to applications: A critical review

Extracellular polymeric substances (EPS) regulated by quorum sensing (QS) could directly mediate adhesion between microorganisms and form tight microbial aggregates. Besides, EPS have redox properties, which can facilitate electron transfer for promoting electroactive bacteria. Currently, the applications research on improving wastewater biological treatment performance based on QS regulated EPS have been widely reported, but reviews on the level of QS regulated EPS to enhance EPS function in microbial systems are still lacking. This work proposes the potential mechanisms of EPS synthesis by QS regulation from the viewpoint of material metabolism and energy metabolism, and summarizes the effects of QS on EPS synthesis. By synthesizing the role of QS in EPS regulation, we further point out the applications of QS-regulated EPS in wastewater biological treatment, which involve a series of aspects such as strengthening microbial colonization, mitigating membrane biofouling, improving the shock resistance of microbial metabolic systems, and strengthening the electron transfer capacity of microbial metabolic systems. According to this comprehensive review, future research on QS-regulated EPS should focus on the exploration of the micro-mechanisms, and economic regulation strategies for QS-regulated EPS should be developed, while the stability of QS-regulated EPS in long-term production experimental research should be further demonstrated.

Quorum sensing in different subcommunities becomes the key factor affecting the humification of the aerobic composting system with sauerkraut fermentation wastewater

Aerobic composting is an effective and harmless method to treat Sauerkraut fermentation wastewater (SFW). Given the limited understanding of the effect of quorum sensing (QS) on humification in subcommunities under acidic environments, a large-scale analysis was conducted to identify features that impact the response of QS to humification in different subcommunities. The results showed that the addition of SFW directly affected humification in subcommunities A and C, and the abundances of functional genes related to carbon fixation and carbon degradation were significantly increased at 7 and 15 d, respectively. In addition, subcommunity B indirectly affected humus production but regulated carbon metabolic pathways such as glycolysis/gluconeogenesis and pentose phosphate by QS with subcommunities B. These findings provide a novel perspective for analysing the regulation of humification in aerobic composting and suggest that composting has potential applications in organic wastewater treatment.

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.

Aerobic composting with sauerkraut fermentation waste water: Increasing the stability and complexity of bacterial community and changing bacterial community assembly processes

Aerobic composting renders the sauerkraut fermentation waste water harmless while adding soluble nutrients. Unravelling the bacterial community assembly processes, changes in community robustness and community cohesion and the relationship between them under composting treatment of sauerkraut fermentation waste water is an interesting topic. Sauerkraut fermentation waste water was used for composting, which increased bacterial linkages, community robustness, competitive behaviour during warming periods and cooperative behaviour during cooling periods, and the control of community assembly processes shifts from deterministic processes (variable selection) to stochastic processes (decentralised limitation). At the same time, the influence of community robustness and community cohesion on community assembly processes was increased. Community cohesion and robustness were significantly correlated with community function. These results indicate that community robustness and community cohesion are critical for the biological handling of hazardous substances.

Response characteristics of Flax retting liquid addition during chicken manure composting: Focusing on core bacteria in organic carbon mineralization and humification

To explore the applicability of flax retting liquid (FRL) addition, the physicochemical properties, microbial community structure and function, carbon conversion and humus (HS) formation were assessed during chicken manure (CM) aerobic composting. Compared with the control group, the addition of FRL increased the temperature at thermophilic phase, while the microbial mass carbon content (MBC) in SCF and FRH groups raised to 96.1±0.25 g/Kg and 93.33±0.27 g/Kg, respectively. Similarly, FRL also improved the concent of humic acid (HA) to 38.44±0.85 g/Kg, 33.06±0.8 g/Kg, respcetively. However, fulvic acid (FA) decreased to 30.02±0.55g/Kg, 31.4±0.43 g/Kg, respectively and further reduced CO₂ emissions. FRL influenced the relative abundance of Firmicutes at thermophilic phase and Ornithinimicrobium at maturity phase. Additionally, FRL strengthen the association among flora and reduce the number of bacteria, which was negative correlated with HA and positive with CO₂ during composting. These findings offer powerful technological support for improving agricultural waste recycling.

Manganese dioxide eliminates the phytotoxicity of aerobic compost products and converts them into a plant friendly organic fertilizer

This study mainly confirmed the exogenous substances (pomace, biochar, MnO₂) and the quorum sensing of bacterial communities jointly regulate the metabolic conversion of toxic substances in manures and agricultural wastes, and converts them into a plant-friendly organic fertilizer through aerobic composting and pot experiment. The results showed the composting products had positive performance in bacterial communities, physicochemical indicators, and phytotoxicity. Meanwhile, the addition of exogenous substances could significantly improve seed germination index, promote metabolites conversion, and optimize bacterial community structure. Furthermore, the exogenous substances mainly regulated the functions of the three bacterial communities by quorum sensing system, then promoted the beneficial metabolites, and inhibited the harmful metabolites. Finally, pot experiments suggested compost products could significantly promote plant growth. Thus, these important discoveries extend the knowledge of the previous work and provide an economical and simple method to convert wastes into organic fertilizers that are friendly to plants and soil.

Artificial intelligence and machine learning approaches in composting process: A review

Studies on developing strategies to predict the stability and performance of the composting process have increased in recent years. Machine learning (ML) has focused on process optimization, prediction of missing data, detection of non-conformities, and managing complex variables. This review investigates the perspectives and challenges of ML and its important algorithms such as Artificial Neural Networks (ANNs), Random Forest (RF), Adaptive-network-based fuzzy inference systems (ANFIS), Support Vector Machines (SVMs), and Deep Neural Networks (DNNs) used in the composting process. In addition, the individual shortcomings and inadequacies of the metrics, which were used as error or performance criteria in the studies, were emphasized. Except for a few studies, it was concluded that Artificial Intelligence (AI) algorithms such as Genetic algorithm (GA), Differential Evaluation Algorithm (DEA), and Particle Swarm Optimization (PSO) were not used in the optimization of the model parameters, but in the optimization of the parameters of the ML algorithms.

Synergistic metabolism of carbon and nitrogen: Cyanate drives nitrogen cycle to conserve nitrogen in composting system

In this study, HCO₃^- was used as a co-substrate for cyanate metabolism to investigate its effect on nitrogen cycle in composting. The results showed that the carbamate content in experimental group (T) with HCO₃^- added was higher than that in control group (CP) during cooling period. Actinobacteria and Proteobacteria were the dominant phyla for cyanate metabolism, and the process was mediated by cyanase gene (cynS). The cynS abundance was 16.6% higher in T than CP. In cooling period, the nitrification gene hao in T was 8.125% higher than CP. Denitrification genes narG, narH, nirK, norB, and nosZ were 25.64%, 35.33%, 45.93%, 36.62%, and 36.12% less than CP, respectively. The nitrogen fixation gene nifH in T was consistently higher than CP in the late composting period. Conclusively, cyanate metabolism drove the nitrogen cycle by promoting nitrification, nitrogen fixation, and inhibiting denitrification, which improved nitrogen retention and compost quality.

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.

Succession and change of potential pathogens in the co-composting of rural sewage sludge and food waste

Composting is an effective way to prevent and control the spread of pathogenic microorganisms which could put potential risk to humans and environment, from rural solid waste, especially sewage sludge and food waste. In the study, we aim to analyze the changes of pathogenic bacteria during the co-composting of rural sewage sludge and food waste. The results showed that only 27 pathogenic bacteria were detected after composting, compared to 50 pathogenic bacteria in the raw mixed pile. About 74% of pathogen concentrations dropped below 1000 copies/g after composting. Lactobacillus, Bacillus, Paenibacillus and Comamonas were the core pathogenic bacteria in the compost, of which concentrations were all significantly lower than that in the raw mixed pile at the end of composting. The concentration of Lactobacillus decreased to 3.03 × 10³ copies/g compared to 0 d with 1.25 × 10⁹ copies/g by the end of the composting, while that of Bacillus, Paenibacillus and Comamonas decreased to 2.77 × 10⁴ copies/g, 2.13 × 10⁴ copies/g and 3.38 × 10² copies/g, respectively, with 1.26 × 10⁷ copies/g, 4.71 × 10⁶ copies/g, 1.69 × 10⁸ copies/g on 0 d. Redundancy analysis (RDA) indicated that physicochemical factors and substances could affect the changes of pathogenic bacteria during composting, while temperature was the key influencing factor. In addition, certain potential pathogenic bacteria, such as Bacteroides-Bifidobacterium, show statistically strong and significant co-occurrence during composting, which may increase the risk of multiple infections and also influence their distribution. These findings provide a theoretical reference for biosafety prevention and control in the treatment and disposal of rural solid waste.