Microbial community composition turnover and function in the mesophilic phase predetermine chicken manure composting efficiency

Substrate preference triggers metabolic patterns of indigenous microbiome during initial composting stages

Composting organic waste is a sustainable recycling method in agricultural systems, yet the microbial preferences for different substrates and their influence on composting efficiency remain underexplored. Here, 210 datasets of published 16S ribosomal DNA amplicon sequences from straw and manure composts worldwide were analyzed, and a database of 278 bacterial isolates was compiled. Substrate-driven microbiome variations were most prominent during the initial composting stages. Indigenous synthetic communities exhibit substrate-specific adaptations, increasing compost temperatures by 2 %-10 %, microbial abundance by 44 %-233 %, and microbial activity by 26 %-60 %. Key dissolved substrates, such as choline and succinic acid in straw compost, and phloretin and uric acid in manure compost, drive these microbial preferences. These findings highlight how substrate-specific microbiomes can be engineered to enhance microbial activity, accelerate temperature rise, and extend the thermophilic phase, providing a targeted framework to improve composting efficiency and tailor strategies to different organic waste types.

Synergistic effects of heterogeneous mature compost and aeration rate on humification and nitrogen fixing during kitchen waste composting

Sludge mature compost (SMC) is notable for its high production, easy accessibility, and stable supply. This study investigated the impact of the SMC addition and different aeration rates on the humification and nitrogen fixing process during kitchen waste composting. The results demonstrated that addition of SMC prolonged the thermophilic phase, as a comparison, increased aeration shortened this phase. The addition of SMC and increased aeration enhanced humus formation and nitrogen retention. SMC introduced more amide and polysaccharide compounds into the compost, promoting the Maillard humification pathway. Additionally, both SMC and high aeration inhibited denitrification: the SMC reduced the abundance of the nirK gene, while high aeration decreased the abundance of nosZ gene. Network analysis revealed that higher aeration enhanced fungal interactions but diminished bacterial interactions. Conversely, SMC addition bolstered both bacterial and fungal interactions. The final compost product with SMC addition showed a 11.56%-44.19% reduction in antibiotic resistance gene content compared with the control group, and heavy metal contents remained within safe application limits. The combination of high SMC addition and high aeration achieved optimal humification and nitrogen retention, underscoring its potential as a promising solution for kitchen waste composting.

Enhancing compost quality through biochar and oyster shell amendments in the co-composting of seaweed and sugar residue

Aquaculture and agricultural production generate substantial amounts of waste, including seaweed (which has plant-stimulating properties), oyster shells, and sugar residues. Through composting and appropriate management, these wastes have the potential to be converted into beneficial soil amendments. However, there is a lack of research exploring the potential of composting in promoting the conversion of seaweed into more stable humified forms, as well as in assessing whether composted seaweed retains its beneficial effects on plant growth. Additionally, studies on using oyster shells as additives to reduce waste pressure and comparing their effectiveness with biochar are relatively scarce. This study examines the impact of incorporating 5% corn stover biochar (T1), 10% biochar (T2), and 10% oyster shell powder (T3) on key physicochemical properties, product quality, and microbial community dynamics during the co-composting of seaweed and sugar residues. Results indicate that organic matter (OM) loss in T1 and T2 increased by 31.2% and 26.4%, respectively, compared to the control (CK). Moreover, Excitation-emission matrix (EEM) fluorescence spectroscopy revealed that humic substances in T1 and T2 surged by 434% and 423%, respectively, far exceeding the 289% increase in CK. The 10% biochar treatment also improved alginate degradation and seed germination index, due to the presence of biostimulants in seaweed and an increased abundance of Cobetia. Microbial analysis post-composting showed that T2 and T3 significantly enhanced the diversity and richness of bacterial communities. Notably, although oyster shell powder did not improve the humification degree of compost as significantly as biochar, it achieved effective weight reduction of waste (OM loss of 43.57%, far exceeding CK's 35.34%) without hindering the composting process. All four compost treatments retained the plant-stimulating effects of seaweed and facilitated alginate degradation. These results underscore the potential of biochar to enhance composting efficiency and utilize composting to process large quantities of oyster shell waste.

Revealing mechanisms of NH3 and N2O emissions reduction in the rapid bio-drying of food waste: Insights from organic nitrogen composition and microbial activity

Inevitably, aerobic biological treatment processes generate emissions of ammonia (NH3) and greenhouse gas (GHGs) emissions, especially nitrous oxide (N2O). The rapid bio-drying process (RBD) for food waste (FW) alleviates issues arising from its substantial growth. However, its emissions of NH3 and N2O remain unknown, and the correlation with nitrogen components in the substrate remains unclear, significantly impeding its widespread adoption. Here, the nitrogen loss and its mechanisms in RBD were investigated, and the results are as follows: The total emission of NH3 and N2O were1.42 and 1.16 mg/kg FW (fresh weight), respectively, achieving a 98 % reduction compared to prior studies. Structural equation modeling demonstrates that acid ammonium nitrogen (AN) decomposition chiefly generates NH3 in compost (p < 0.001). Strong correlation (p < 0.001) exists between amino acid nitrogen (AAN) and AN. In-depth analysis of microbial succession during the process reveals that the enrichment of Brevibacterium, Corynebacterium, Dietzia, Fastidiosipila, Lactobacillus, Mycobacterium, Peptoniphilus, and Truepera, are conducive to reducing the accumulation of AN and AAN in the substrate, minimizing NH3 emissions (p < 0.05). While Pseudomonas, Denitrobacterium, Nitrospira, and Bacillus are identified as key species contributing to N2O emissions during the process. Correlation analysis between physicochemical conditions and microbial succession in the system indicates that the moisture content and NO3- levels during the composting process provide suitable conditions for the growth of bacteria that contribute to NH3 and N2O emissions reduction, these enrichment in RBD process minimizing NH3 and N2O emissions. This study can offer crucial theoretical and data support for the resource utilization process of perishable organic solid waste, mitigating NH3 and GHGs emissions.

A multi-criteria approach to test and evaluate the efficiency of two composting systems under two different climates

The selection of the appropriate composting system, climate conditions, and duration of the composting process are important parameters for municipal solid waste composting. Therefore, this research aimed to design, test, and evaluate two different static composting systems under two different climate regions, Palestine and India, following a multi-criteria approach. A forced-aeration composting system was designed for use in Palestine, and a naturally aerated one was used in India. Three experiments were conducted, two of them in Palestine and one in India. The operational parameters were controlled and monitored during the composting process, while the physio-chemical and biological parameters were tested to evaluate the compost end quality. The results showed that both systems provide good efficiency toward formation of final compost (39-43 days in Palestine, and 31 days in India), and the average materials' volume reduction was almost 60%. The physio-chemical analysis showed that most of the parameters comply with the threshold limits specified by the Palestinian Standards Institution (PSI) and Indian Fertilizer Control Order (FCO) except for minor deviations. Both systems provided a high fertility index (4.3, 4.7, and 4.8), and a high clean index (4.6, 5.0, and 4.7). However, the results of the biological parameters showed that all the experiments met PSI, but none of them met FCO, suggesting that the outer edges of the composting system didn't heat enough to inactivate pathogenic microbes, therefore, developing the system by adding turning option could overcome this shortcoming. It was concluded that the forced aeration system is suitable for Palestine, while the natural aeration system is suitable for India.Implications: Municipal solid waste management is facing technical and financial challenges worldwide due to the increasing generation of solid waste following the population growth. The current improper management of this waste stream through landfilling is adding pressure on the environment as a result of methane emissions and landfill leachate. Therefore, composting of the organic fraction through selection of an appropriate composting system can solve many waste management problems and contribute to environmental sustainability. This research focuses on design, test and evaluate two composting systems in two regions with different climatic conditions, Palestine and India as both are facing waste management problems. The outcome of this research optimized the composting process which can be replicated and scaled up in other countries worldwide with similar climatic conditions.

Evaluation of gases emission and enzyme dynamics in sheep manure compost occupying with peach shell biochar

The effect of peach shell biochar (PSB) amendment on sheep manure (SM) composting was investigated. Five different ratios of PSB were applied (0%, 2.5%, 5%, 7.5%, and 10% PSB), and named T1 to T5, and run 50 days of composting experiment. It was found that PSB (especially 7.5% and 10%) could improve the compost environment, regulate the activity of microorganisms and related enzymes, and promote the decomposition of compost. 7.5% and 10% PSB advanced the heap into the thermophilic stage and increased the maximum temperature, while also increasing the germination index by 1.40 and 1.39 times compared to control. Importantly, 10% PSB effectively retained more than 60% of carbon and 55% of nitrogen by inhibiting the excess release of NH3 and greenhouse gases. High proportion PSB amendment increased the activity of dehydrogenase and cellulase, but inhibited protease and urease. The correlation results indicated that PSB changed the key bacterial genus, and there was a stronger association with environmental factors at 7.5% and 10%. Therefore, 7.5% and 10% peach shell biochar can be used as appropriate proportions to improve composting conditions.

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

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

Multi-stage aeration regime to regulate organic conversion toward gas alleviation and humification in food waste digestate composting

Aerobic composting has been considered as a pragmatic technique to convert food waste digestate into high-quality biofertiliser. Nevertheless, massive gaseous emission and immature product remain the primary challenges in food waste digestate composting. Thus, the performance of multi-stage aeration regimes to improve gaseous emissions and organic humification during food waste digestate composting was investigated in this study. In addition to continuous aeration with a constant intensity of 0.3 L kg·dry mass (DM)-1·min-1, two multi-stage decreased aeration regimes were designed as "0.3-0.2-0.1" and "0.3-0.1-0.1" L·kg·DM-1·min-1 from the thermophilic to cooling and then mature stages, respectively. Results showed that the decreased aeration regimes could alleviate nitrous oxide (N2O) and ammonia (NH3) emission and slightly enhance humification during composting. The alleviated N2O and NH3 emission were mainly contributed by abiotically reducing gaseous release potential as well as biotically inactivating denitrifers (Pusillimonas and Pseudidiomarina) and proliferating Atopobium to reduce nitrate availability under lower aeration supply. The "0.3-0.2-0.1 L kg·DM-1·min-1" regime exhibited a more excellent performance to alleviate N2O and NH3 emission by 27.5% and 16.3%, respectively. Moreover, the decreased aeration regimes also favored the enrichment of functional bacteria (Caldicoprobacter and Syntrophomonas) to accelerate lignocellulosic biodegradation and thus humic acid synthesis by 6.5%-11.2%. Given its better performance to improve gaseous emissions and humification, the aeration regime of "0.3-0.2-0.1 L kg·DM-1·min-1" are recommended in food waste digestate composting in practice.

Biotic pathways of reciprocal responses between antibiotic resistance genes and inorganic nitrogen cycling genes in amoxicillin-stressed compost ecosystems

This study explored the transformation of inorganic nitrogen, the expression levels of antibiotic resistance genes (ARGs), and the regulatory mechanisms of key species on ARGs and inorganic nitrogen cycling genes (INCGs) under different levels of amoxicillin (AMX) stress. High level of AMX inhibited the accumulation of NH4+-N, which increased by 531 % relative to the initial. Moreover, AMX to some extent increased the levels of nirS and nirK, which could potentially result in nitrogen loss and the accumulation of NO2-. Actinobacteria might serve as potential hosts for ARGs during sludge composting. This stress induced a complex response between INCGs and ARGs more complex due to key species. Under high-level AMX pressure, most species associated with ARGs likely derived from nitrogen cycling functional species. To conclude, high levels of AMX stress might lead to nitrogen cycling imbalance and the dissemination of antibiotic resistance genes in composting systems.

Greenhouse gas emission characteristics and influencing factors of agricultural waste composting process: A review

China, being a major agricultural nation, employs aerobic composting as an efficient approach to handle agricultural solid waste. Nevertheless, the composting process is often accompanied by greenhouse gas emissions, which are known contributors to global warming. Therefore, it is urgent to control the formation and emission of greenhouse gases from composting. This study provides a comprehensive analysis of the mechanisms underlying the production of nitrous oxide, methane, and carbon dioxide during the composting process of agricultural wastes. Additionally, it proposes an overview of the variables that affect greenhouse gas emissions, including the types of agricultural wastes (straw, livestock manure), the specifications for compost (pile size, aeration). The key factors of greenhouse gas emissions during composting process like physicochemical parameters, additives, and specific composting techniques (reuse of mature compost products, ultra-high-temperature composting, and electric-field-assisted composting) are summarized. Finally, it suggests directions and perspectives for future research. This study establishes a theoretical foundation for achieving carbon neutrality and promoting environmentally-friendly composting practices.

Alternating ventilation accelerates the mineralization and humification of food waste by optimizing the temperature-oxygen-moisture distribution in the static composting reactor

Traditional unidirectional ventilation often leads to the loss of heat and moisture during composting, disrupting the favorable microenvironment required for aerobic microbes. This study developed a pulse alternating ventilation composting reactor and investigated the effects of alternating ventilation on composting efficiency compared with upward ventilation and downward ventilation. The results demonstrated that alternating ventilation stabilized the moisture content at approximately 60 % while reducing the temperature and oxygen concentration range within the reactor. Moreover, it extended the duration of high-temperature (>50 °C) by 31 % and 75 % compared to other two groups. It improved the microbial cooperation intensity and stimulated the core microbe (Tepidimicrobium). Seed germination index (GI) of the compost was improved (GI = 91.27 %), and the humic acid content was 1.23 times and 1.37 times higher than other two groups. These results showed that alternating ventilation can be used for efficient resource disposal of food waste.

Microbial agents obtained from tomato straw composting effectively promote tomato straw compost maturation and improve compost quality

Appropriate management of agricultural organic waste (AOW) presents a significant obstacle in the endeavor to attain sustainable agricultural development. The proper management of AOW is a necessity for sustainable agricultural development. This can be done skillfully by incorporating microbial agents in the composting procedure. In this study, we isolated relevant bacteria strains from tomato straw AOW, which demonstrated efficient degradation of lignocellulose without any antagonistic effects in them. These strains were then combined to create a composite microbial agent called Zyco Shield (ZS). The performance of ZS was compared with a commercially effective microorganism (EM) and a control CK. The results indicate that the ZS treatment significantly prolonged the elevated temperature phase of the tomato straw pile, showing considerable degradation of lignocellulosic material. This substantial degradation did not happen in the EM and CK treatments. Moreover, there was a temperature rise of 4-6 ℃ in 2 days of thermophilic phase, which was not the case in the EM and CK treatments. Furthermore, the inoculation of ZS substantially enhanced the degradation of organic waste derived from tomato straw. This method increased the nutrient content of the resulting compost and elevated the enzymatic activity of lignocellulose-degrading enzymes, while reducing the urease enzyme activity within the pile. The concentrations of NH4+-N and NO3--N showed increases of (2.13% and 47.51%), (14.81% and 32.17%) respectively, which is again very different from the results of the EM and CK treatments. To some extent, the alterations observed in the microbial community and the abundance of functional microorganisms provide indirect evidence supporting the fact that the addition of ZS microbial agent facilitates the composting process of tomato straw. Moreover, we confirmed the degradation process of tomato straw through X-ray diffraction, Fourier infrared spectroscopy, and by scanning electron microscopy to analyze the role of ZS microbial inoculum composting. Consequently, reinoculation compost strains improves agricultural waste composting efficiency and enhances product quality.

Moderately delayed maturation of composting promotes the reduction of guild-plant pathogenic fungi within vegetable waste

The relationships among the relative abundance of guild-plant pathogenic fungi, compost maturation index, and microbial community variation during vegetable waste composting, which are influenced by the C/N ratio, remain poorly understood. To address this, fungal communities were analyzed in composting treatments with C/N ratios of approximately 15 (CN15) and 25 (CN25), using vegetable waste as the primary raw material. The CN15 treatment showed greater microbial community variation and a better overall compost maturation index value than the CN25 treatment. However, the CN25 treatment had a greater decline in plant-pathogenic fungi than the CN15 treatment. Notably, the relative abundance of guild-plant pathogenic fungi was significantly negatively related to the compost maturity index in the CN25 treatment, while no significant relationship was observed in the CN15 treatment. This study suggests that the moderately delayed maturation of composting is beneficial for reducing guild-plant pathogenic fungi in vegetable waste.

Evolution of fungal and non-fungal eukaryotic communities in response to thermophilic co-composting of various nitrogen-rich green feedstocks

Thermophilic composting is a promising soil and waste management approach involving diverse micro and macro-organisms, including eukaryotes. Due to sub-optimal amounts of nutrients in manure, supplemental feedstock materials such as Lantana camara, and Tithonia diversifolia twigs are used in composting. These materials have, however, been reported to have antimicrobial activity in in-vitro experiments. Furthermore, the phytochemical analysis has shown differences in their complexities, thus possibly requiring various periods to break down. Therefore, it is necessary to understand these materials' influence on the biological and physical-chemical stability of compost. Most compost microbiome studies have been bacterial-centric, leaving out eukaryotes despite their critical role in the environment. Here, the influence of different green feedstock on the fungal and non-fungal eukaryotic community structure in a thermophilic compost environment was examined. Total community fungal and non-fungal eukaryotic DNA was recovered from triplicate compost samples of four experimental regimes. Sequencing for fungal ITS and non-fungal eukaryotes; 18S rDNA was done under the Illumina Miseq platform, and bioinformatics analysis was done using Divisive Amplicon Denoising Algorithm version 2 workflow in R version 4.1. Samples of mixed compost and composting day 84 recorded significantly (P<0.05) higher overall fungal populations, while Lantana-based compost and composting day 84 revealed the highest fungal community diversity. Non-fungal eukaryotic richness was significantly (P< 0.05) more abundant in Tithonia-based compost and composting day 21. The most diverse non-fungal eukaryotic biome was in the Tithonia-based compost and composting day 84. Sordariomycetes and Holozoa were the most contributors to the fungal and non-fungal community interactions in the compost environment, respectively. The findings of this study unravel the inherent influence of diverse composting materials and days on the eukaryotic community structure and compost's biological and chemical stability.

Aerobic co-composting of mature compost with cattle manure: organic matter conversion and microbial community characterization

The production of organic fertilizer by aerobic composting of cattle manure is an important way of its resource utilization. This study evaluated the effects of adding mature compost on the decomposition and microbial communities in the aerobic composting of cattle manure. The addition of mature compost shortens the composting cycle and results in a final lignocellulosic degradation rate of 35%. Metagenomic analysis showed that this was due to the proliferation of thermophilic and organic matter-degrading functional microorganisms, which enhanced the activity of carbohydrate-active enzymes. With the addition of mature compost, the microbial community exhibited stronger metabolic functions, especially carbohydrate and amino acid metabolism, which are the driving forces of organic matter degradation. This study deepens the understanding of organic matter conversion and microbial community metabolic functions when mature compost is used for livestock manure composting and provides a promising technology for livestock manure composting.

Inoculation enhances directional humification by increasing microbial interaction intensity in food waste composting

Inoculation can effectively improve the recycling level of organic waste in composting process. However, the role of inocula in the humification process has been rarely studied. Therefore, we constructed a simulated food waste composting system by adding commercial microbial agents to explore the function of inocula. The results showed that adding microbial agents extended the high temperature maintenance time by 33% and increased the humic acid content by 42%. Inoculation significantly improved the degree of directional humification (HA/TOC = 0.46, p < 0.001). The proportion of positive cohesion in the microbial community underwent an overall increase. The strength of bacterial/fungal community interaction increased by 1.27-fold after inoculation. Furthermore, the inoculum stimulated the potential functional microbes (Thermobifida and Acremonium) which were highly related to the formation of humic acid and the degradation of organic matter. This study showed that additional microbial agents could strengthen microbial interaction to raise the humic acid content, thus opening the door for the development of targeted biotransformation inocula in the future.

Matured compost amendment improves compost nutrient content by changing the bacterial community during the composting of Chinese herb residues

Composting is a sustainable strategy to deal with organic waste. Our research aimed to study the influence of an amendment of 10% matured compost (MC) during Chinese herb residue (CHR) compost. Here, a 60-day CHR compost was performed, and MC application was able to reduce the nitrogen loss and enhance the humic acid accumulation during the composting as compared with the non-inoculated control (NC), by 25 and 19%, respectively. Furthermore, the matured compost amendment improved the diversity of the bacterial community, increased the complexity of the co-occurrence network, and changed the keystone and module hub bacteria during composting. The increased abundance levels of Thermopolyspora, Thermobispora, and Thermosporomyces, which were significantly higher in MC than in NC, may contribute to the degradation of cellulose and the formation of humic acid. Overall, this study extends our understanding of the effects of matured compost reflux on compost quality and the bacterial community.

Response characteristics of antibiotic resistance genes and bacterial communities during agricultural waste composting: Focusing on biogas residue combined with biochar amendments

This research investigated biogas residue and biochar addition on antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and changes in bacterial community during agricultural waste composting. Sequencing technique investigated bacterial community structure and ARGs, MGEs changes. Correlations among physicochemical factors, ARGs, MGEs, and bacterial community structure were determined using redundancy analysis. Results confirmed that biochar and biogas residue amendments effectively lowered the contents of ARGs and MGEs. The main ARGs detected was sul1. Proteobacteria and Firmicutes were the main host bacteria strongly associated with the dissemination of ARGs. The dynamic characteristics of the bacterial community were strongly correlated with pile temperature and pH (P < 0.05). Redundancy and network analysis revealed that nitrate, intI1, and Firmicutes mainly affected the in ARGs changes. Therefore, regulating these key variables would effectively suppress the ARGs spread and risk of compost use.

Enhancing the compost maturation of deer manure and corn straw by supplementation via black liquor

In this paper, the relationship between black liquor and microbial growth, enzymatic secretion and humus formation in composting was studied. The results showed that black liquor inoculation is an effective way to promote fermentation process. After black liquor inoculation, the abundance of Corynebacterium, Aequorivita, and Pedobacter, which have the catalase and oxidase activity, has been significantly increased. The enzymatic activity of alkaline phosphatase, catalase, peroxidase and invertase was 40 mg/(g·24h), 6.5 mg/(g·20 min), 13 100 mg/(g·24h), and 6100 mg/(g·24h) respectively at day 18. Humic acid and fulvic acid concentration was 12 g/kg and 11 g/kg which is higher than that of the treatments of no black liquor inoculation. The results suggested that black liquor inoculation was beneficial to indigenous microorganisms reproduce efficiently, then the secretion of enzymes related to cellulose, hemicellulose, and lipid hydrolysis, and the formation of humic substances.

Effects of biochar on the degradation of organophosphate esters in sewage sludge aerobic composting

In this study, the impact of biochar on the degradation of organophosphate esters (OPEs) during the aerobic composting of sewage sludge was investigated. Three treatments were conducted with different percentages of biochar in the compost, including 5 %, 10 %, and 20 %. The treatment with 10 % of biochar showed the longest thermophilic phase compared to that of 5 % and 20 % of biochar, which greatly promoted the decomposition of organic matter. In addition, the degradation rate of the hard-to-degrade chlorinated-OPEs was significantly increased by 10 % biochar, reaching to 57.2 %. Correspondingly, approximately 43.6 % of the total concentration of OPEs (Σ₆OPEs) was eliminated in the presence of 10 % of biochar, which was higher than the treatments with 5 % and 20 % of biochar. Biochar significantly influenced the microbial community structure of compost, but the previously reported organophosphorus-degrading bacteria did not play a major role in the degradation of OPEs. The redox ability of the increased oxygen-containing functional groups such as quinone on the surface of biochar and the biochar-mediated electron transfer ability may play an essential role in the degradation of OPEs during the composting process.

Continuing progress in the field of two-dimensional correlation spectroscopy (2D-COS): Part III. Versatile applications

In this review, the comprehensive summary of two-dimensional correlation spectroscopy (2D-COS) for the last two years is covered. The remarkable applications of 2D-COS in diverse fields using many types of probes and perturbations for the last two years are highlighted. IR spectroscopy is still the most popular probe in 2D-COS during the last two years. Applications in fluorescence and Raman spectroscopy are also very popularly used. In the external perturbations applied in 2D-COS, variations in concentration, pH, and relative compositions are dramatically increased during the last two years. Temperature is still the most used effect, but it is slightly decreased compared to two years ago. 2D-COS has been applied to diverse systems, such as environments, natural products, polymers, food, proteins and peptides, solutions, mixtures, nano materials, pharmaceuticals, and others. Especially, biological and environmental applications have significantly emerged. This survey review paper shows that 2D-COS is an actively evolving and expanding field.

Exploring the mechanism associated with methane emissions during composting: Inoculation with lignocellulose-degrading microorganisms

Inoculation with microorganisms is an effective strategy for improving traditional composting processes. This study explored the effects of inoculation with lignocellulose-degrading microorganisms (LDM) on the degradation of organic matter (OM), methane (CH₄) emissions, and the microbial community (bacteria and methanogens) during composting. The results showed that LDM accelerated the degradation of OM (including the lignocellulose fraction) and increased the CH₄ releases in the later thermophilic and cooling stages during composting. At the ending of composting, LDM increased the CH₄ emissions by 38.6% compared with the control. Moreover, LDM significantly increased the abundances of members of the bacterial and methanogenic community during the later thermophilic period (P < 0.05). In addition, LDM promoted the growth and activity of major bacterial genera (e.g., Ureibacillus) with the ability to degrade macromolecular OM, as well as affecting key methanogens (e.g., Methanocorpusculum) in the composting system. Network analysis and variance partitioning analysis indicated that OM and temperature were the main factors that affected the bacterial and methanogen community structures. Structural equation modeling demonstrated that the higher CH₄ emissions under LDM were related to the growth of methanogens, which was facilitated by the anaerobic environment produced by large amounts of CO₂. Thus, aerobic conditions should be improved during the end of the thermophilic and cooling composting period when inoculating with lignocellulose-degrading microorganisms in order to reduce CH₄ emissions.

Effect of post-production vermicompost and thermophilic compost blending on nutrient availability

Composting is a common waste management strategy for recycling nutrients from organic household or agricultural wastes. However, thermophilic (e.g. windrow) composting and vermicomposting (using earthworms) produce different nutrient and enzyme profiles. Vermicompost is purported to have greater fertility benefits, but is also more expensive than thermophilic compost. The objective of this study was to examine a novel approach to designing organic fertility amendments by blending mature vermicompost and thermophilic compost. To examine the effect of blending, vermicompost was admixed to thermophilic compost at 20, 50 and 70 % by mass, with and without the addition of coir (cocopeat). Electric conductivity, water-extractable, immediately available N, P and K were measured. Vermicompost and coir synergistically affected the availability of these nutrients. Synergistic effects were between 15 and 40 % for total inorganic N in blends with coir. Without coir, synergism occurred only at vermicompost additions ≥50 %. Synergism for available P and K was present in all blends and ranged from 10% to 35%. Electrical conductivity measurements suggest that blending affected compost within three days of starting the incubation. The activity of five of seven measured enzymes were linearly and positively related to the fraction of vermicompost in the blend. Blending mature composts with differing properties may be another tool, in addition to adjusting feedstock and process parameters, to affect positively the fertility properties of composts.

Characteristics of carbon, nitrogen, phosphorus and sulfur cycling genes, microbial community metabolism and key influencing factors during composting process supplemented with biochar and biogas residue

Carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycling functional genes and bacterial and fungal communities during composting with biochar and biogas residue amendments were studied. Correlations between microbial community structure, functional genes and physicochemical properties were investigated by network analysis and redundancy analysis. It was shown that the gene of acsA abundance accounted for about 50% of the C-related genes. Biogas residue significantly decreased the abundance of denitrification gene nirK. Biogas residues can better promote the diversity of bacteria and fungi during composting. Biochar significantly increased the abundance of Humicola. Redundancy analysis indicated that pile temperature, pH, EC were the main physicochemical factors affecting the microbial community. WSC and NO₃^--N have significant correlation with C, N, P, S functional genes. The research provides a theoretical basis for clarifying the metabolic characteristics of microbial communities during composting and for the application of biochar and biogas residues in composting.

Effect of microbial agents on maturity, humification, and stability and the bacterial succession of spent mushroom substrate composting

Two composting experiments were conducted to investigate the effects of commercial microbial agents on microbial succession and nutrient flow such as humification, maturation, and stability during the aerobic composting of the spent mushroom substrate (SMS). The cellulose degradation rate of T (added microbial agents at the initial stage) reached 41.8%, which was much significantly (p < 0.05) higher than that of CK (14.9%). The seed germination index (GI) in T (82.38%) was significantly (p < 0.05) higher than that in CK (74.74%) in the maturation phase. Moreover, the total organic carbon/total nitrogen ratio (C/N) and electrical conductivity (EC) value of T decreased to 10.5 and 2.37 mS/cm, respectively. Chemical detection and fluorescence excitation-emission region integration method (EEM-FRI) analysis showed that the microbial agents significantly accelerated the organic matter (OM) decomposition and promoted the quality of mature compost using SMS as a single raw material. The bacterial abundance of T was significantly richer than the CK due to the addition of microbial agents. The results could provide a comprehensive understanding of adding microbial agents into composting SMS and a scientific feasibility strategy to rational utilization of resources in the edible fungi industry, which was conducive to the waste management and sustainable development of the edible fungi industry.

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

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

Insight into the fraction variations of selenium and their effects on humification during composting

This study investigated the variation of selenium fractions and their effects on humification during composting. Selenite and selenate were added to a mixture of goat manure and wheat straw for composting. The results demonstrated that the bioavailable Se in the selenite added treatment (9.3-13.8%) was lower than in the selenate added treatment (18.1-47.3%). Meanwhile, the HA/FA of selenite and selenate added treatments were higher than in control, indicating that the selenium addition (especially selenite) promoted the humification of composting. Importantly, selenite enriched the abundance of Tepidimicrobium and Virgibacillus which were responsible to improve humification performance. Selenate increased the abundance of Thermobifida and Cellvibrio which facilitated the composting humification. The genes encoding CAZymes involved in the degradation of organic materials were also analyzed, and selenium could contribute to the synthesis of humus. KEGG pathway analysis revealed that the selenite addition promoted amino acids and carbohydrate metabolism compared to the control.

Insight into structural composition of dissolved organic matter in saline-alkali soil by fluorescence spectroscopy coupled with self-organizing map and structural equation modeling

Soil salinization has been occurring all over the world, which severely affected crop production and threatened the life of mankind. It is necessary to take serious steps to improve soil fertility for the sustainability and productive capacity of agriculture. Soil samples of different depths were collected from native vegetation communities (Comm. Phragmites communis (CPC) and Comm. Populus alba (CPA)) and irrigated crops (corn fields (CFD) and seed melon fields (SMF)) in Hetao irrigation area of China. Three dimensional excitation-emission matrix (EEM) fluorescence technology combined with self-organizing map were used to analyze the dissolved organic matter (DOM) composition and structural characteristics in saline-alkali soils and its spatial distribution under different vegetation covers. Critical factors were recognized by classification and regression tree (CART) for distinguishing soil samples, and latent factors were revealed with structural equation modeling (SEM) for improving the humification degree of DOM from saline soils in Hetao irrigation area. Five components were obtained in the DOM substances, i.e., tyrosine-like (C1), tryptophan-like (C2), UV fulvic-like (C3), visible fulvic-like (C4) and humic-like (C5). The protein-like peaks were all obvious, and the fulvic-like peaks (600-735 a.u.) were conspicuous in the CPC soil than in others, except CFD1 and SMF1. C1 was the critical factor to distinguish native vegetation from irrigated crops, and C1 and C2 were the critical factors to distinguish CFD from SMF. Contrary to the HA/FA (0.20) and A/C (0.25), the path coefficient (-0.15) of sources with T/H was negative, indicating that the incremental contents of fluorenscense substances were in the sequences of protein-like > visible fulvic-like > UV fulvic-like > humic-like, affecting by the allochthonous. C1 (1.00) and C4 (1.00) were the primary components for improving the humification degree of DOM, which were principally originated from plant debris. EEM combined with self-organizing map, CART and SEM is an efficient way to distinguish different salinized soils and reveal the latent factors for improving the soil fertility.

Effects of biochar and biogas residue amendments on N2O emission, enzyme activities and functional genes related with nitrification and denitrification during rice straw composting

This study was carried out to determine the response characteristics of N₂O emission, enzyme activities, and functional gene abundances involved in nitrification/denitirification process with biochar and biogas residue amendments during rice straw composting. The results revealed that N₂O release mainly occurred during the second fermentation phase. Biogas residue amendment promoted N₂O emission, while biochar addition decreased its emission by 33.6%. The nirK gene was abundant through composting process. Biogas residues increased the abundance of denitrification genes, resulting in further release of N₂O. Biochar enhanced nosZ gene abundance and accelerated the reduction of N₂O. Nitrate reductase (NR), nitrite reductase (NiR), N₂O reductase (N₂OR), and ammonia monooxygenase (AMO) activities were greatly stimulated by biochar or biogas residue rather than their combined addition. Pearson regression analysis indicated that N₂O emission negatively correlated with ammonium and positively correlated with nosZ, nirK, 18S rDNA, total nitrogen, and nitrate (P < 0.05).

Process monitoring of photocatalytic degradation of 2,4-dinitrotoluene by Au-decorated Fe3O4@TiO2 nanoparticles: surface-enhanced Raman scattering method

Recently, the degradation and detection of 2,4-dinitrotoluene (2,4-DNT) capable of producing 2,4,6-trinitrotoluene (TNT) for environmental and human health risks have been developed. We prepared photoresponsive Au-decorated Fe₃O₄@TiO₂ nanoparticles (Fe₃O₄@TiO₂-Au NPs) under sunlight simulated Xe lamp irradiation. The photodegradation process of 2,4-DNT by Fe₃O₄@TiO₂-Au NPs was successfully monitored by surface-enhanced Raman scattering (SERS). Since SERS monitoring shows intrinsic information about the molecular structure, it was possible to predict the photodegradation of 2,4-DNT. The 2,4-DNT photodegradation mechanism based on two-dimensional correlation spectroscopy (2D-COS), which provides very beneficial information for a deeper understanding of systems, has been identified. We confirmed that Fe₃O₄@TiO₂-Au NPs can be widely used in organic pollutant degradation under sunlight. Furthermore, the combination of SERS based process monitoring and 2D-COS can be a convincing analytical technique for photodegradation studies of organic pollutants.

Independent and combined effects of antibiotic stress and EM microbial agent on the nitrogen and humus transformation and bacterial community successions during the chicken manure composting

This study aimed to investigate the independent and combined effects of antibiotic and EM microbial agent on the nitrogen and humus (HS) transformations as well as the bacterial community successions during the chicken manure and rice husk composting. EM microbial agent accelerated the oxytetracycline (OTC) degradation, but slowed down the norfloxacin (NOR) degradation. OTC inhibited the TN retention and promoted the HS accumulation, both NOR and EM microbial agent inhibited the TN retention and HS accumulation, while EM microbial agent showed an antagonistic effect on TN immobilization with antibiotics and reduced the impacts of antibiotics on HS. Obvious bacterial community successions occurred. Firmicutes were related to HS transformation, while Firmicutes, Actinobacteriota and Proteobacteria were associated with nitrogen conversion. NOR promoted the transformations of NH₄⁺-N to NO₃^--N and FA to HA. The findings provided theoretical data for the recycle of antibiotic-contaminated manure and the efficient production of high-quality compost.

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

Chicken manure containing antibiotics is a hazardous biological waste. The purpose of our study was to investigate how different concentrations of penicillin G alter the bacterial community to affect humification during aerobic composting of chicken manure. The effect of quorum sensing on the bacterial community was also evaluated. Penicillin G mainly affects low fold changes (within 4) for low-abundance (within 200) microbial genera. We found that the bacterial community cooperated to regulate humus and humic acid synthesis. The microbial genera that make up the bacterial community are different, but each bacterial community may have the same ecological function. Quorum sensing affects humic acid synthesis by regulating carbohydrate metabolism and amino acid metabolism in bacterial communities through mechanisms such as the pentose phosphate pathway and the shikimate pathway. This work presents an understanding of the impact of quorum sensing on the collaboration between bacterial communities during composting.

Short-term biodrying achieves compost maturity and significantly reduces antibiotic resistance genes during semi-continuous food waste composting inoculated with mature compost

Food waste (FW) is important object of resource utilization and source of antibiotic resistance genes (ARGs). This study investigated the effects of biodrying combined with inoculating mature compost (B&M) on the composting efficiency, succession of bacterial communities and their links with metabolism functions as well as the fate of ARGs during FW composting. The results showed that B&M could rapidly raise and maintain high relative abundance of Bacillaceae (66.59-94.44%) as well as composting temperature (45.86-65.86 ℃), so as to achieve the final maturity of FW composting in a short time by regulating microbial carbohydrate (14.02-15.31%) and amino acid metabolism (10.33-12.47%). Network analysis demonstrated that high temperature could effectively inhibit the proliferation and spread of potential bacterial hosts of ARGs and integrons including Lactobacillaceae, Enterobacteriaceae, Leuconostocaceae and Corynebacteriaceae during the first two days of composting. As a result, B&M significantly reduced the absolute (72.09-99.47%) and relative abundances (0.31-2.44 logs) of nearly all ARGs especially ermB, tetM, bla_CTX-M and bla_OXA. Present study deepened the knowledge of ARGs variation, succession and metabolism functions of bacterial communities when B&M processes were used for FW composting, suggesting a promising technology for reducing the transmission risk of ARGs and reaching maturity of FW composting.

Addition of mature compost improves the composting of green waste

Composting is an environmentally friendly and effective way to dispose of green waste (GW), but traditional composting of GW is slow and results in the loss of many nutrients and a poor-quality compost product. In this study, mature compost (MC), which may function as an inexpensive and readily available microbial inoculant, was added to GW at 15, 20, 25, and 30% (w/w, dry weight basis) (treatments T2-T5, respectively); GW with 0.5% (v/w, dry weight basis) commercial microbial inoculum served as T1, and GW without any microbial inoculant served as the control. The treatment that produced the highest quality compost was determined based on the following compost properties: temperature, bulk density, porosity, pH, electric conductivity, contents of organic matter and nutrients, Fourier-transform infrared spectroscopy data, and phytotoxicity. The results showed that addition of 25% MC resulted in the best quality product in only 40 days.

Deciphering the dominant components and functions of bacterial communities for lignocellulose degradation at the composting thermophilic phase

The decomposition and transformation of organic matters during composting process are performed by various microorganisms. However, the bacterial communities and their functions usually vary with composting materials. Here the dominant bacterial genera and their functions were identified at the thermophilic phase during composting of mulberry branches with silkworm excrement (MSE), pig manure (MPM) and cow manure (MCD). The activities of β-glucosidase and endoglucanase were highest for MCD (1.31 and 17.15 µg g^-1 min^-1) and lowest for MPM (0.92 and 14.22 µg g^-1 min^-1). Random Forest model and correlation analysis revealed that Stenotrophomonas, Bacillus, and Sinibacillus were the dominant bacterial genera involved in lignocellulose degradation regardless of composting materials. Carbohydrate metabolism, amino acid metabolism, and DNA replication and repair were primary functions of the bacterial communities for the three types of composting. The quantification of lignocellulose degradation genes further verified the dominant functions of the bacterial communities.

Process optimization by combining in-vessel composting and vermicomposting of vegetable waste

The process parameters of in-vessel rotary drum composting (RDC) with vermicomposting (VC) were investigated for the conversion of vegetable waste into vermicompost. After 7-day initial thermophilic exposure (maximal 51.5 °C in 24 h), the partially degraded RDC waste was divided into R1 (no vermiculture), R2, R3, and R4 (with Eudrilus eugeniae; Eisenia fetida; and Perionyx excavates monocultures, respectively). R3 derived vermicompost displayed maximum optimal process parameters and desirable compost qualities. Against the constant 2.2% nitrogen content of R1, an increase from 1.4 to 4.15% was seen in R3, with a 52.5% reduction in total organic carbon (TOC). A clear testimony to the enhanced nutritional content and fitness of the novel combination of RDC thermophilic biodegradation and E. fetida based vermicomposting. In an environmentally compatible mode, the faster organic deconstruction in 27 days could substantially alter organic waste treatment in the immediate future.

Different Effects of Thermophilic Microbiological Inoculation With and Without Biochar on Physicochemical Characteristics and Bacterial Communities in Pig Manure Composting

This study evaluated the effects of thermophilic microbiological inoculation alone (TA) and integrated with biochar (TB) on the physicochemical characteristics and bacterial communities in pig manure (PM) composting with wheat straw. Both TA and TB accelerated the rate of temperature increase during the PM composting. TA significantly reduced total nitrogen loss by 18.03% as opposed to TB which significantly accelerated total organic carbon degradation by 12.21% compared with the control. Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria were the major phyla in composting. Variation of the relative abundance of genera depended on the composting period and treatment. The genera Lactobacillus (26.88-46.71%) and Clostridium_sensu_stricto (9.03-31.69%) occupied a superior position in the temperature rise stage, and Bacillus (30.90-36.19%) was outstanding in the cooling stage. Temperature, total nitrogen (TN), and ammonium nitrogen significantly influenced the bacterial phyla composition. TN, water content, and nitrite nitrogen were the main drivers of the bacterial community genera. Furthermore, our results demonstrated that microbiological consortia were resistant to high temperatures and could fix nitrogen for enriched Pseudomonas; however, when interacted with biochar, total organic carbon (TOC) degradation was accelerated for higher bacterial richness and diversity as well as overrepresented Corynebacterium.

Accelerated humification and alteration of microbial communities by distillers' grains addition during rice straw composting

This research explored the influence of distillers' grains amendment on the humification performance and microbial communities during rice straw composting. The composition of dissolved organic matter and maturity index were analyzed by the fluorescence excitation emission matrix spectroscopy and parallel factor analysis. High-throughput sequencing and redundancy analysis were employed for revealing the structure dynamics for microbial community and their shaping factors, respectively. Results indicated that addition of distillers' grains effectively increased the microbial activity, which was beneficial to the organic matter degradation and nitrogen conservation. Microbial community structures were significantly changed with different amendment strategies. Nitrate, water soluble carbon, organic matter, ammonium were the key parameters influencing the variation of bacterial community in different treatments. Water soluble carbon significantly affected the dominant fungal community dynamics. These results showed that addition of distillers' grains effectively improved the nutritional status and changed the microbial communities during rice straw composting.

The quality of compost was improved by low concentrations of fulvic acid owing to its optimization of the exceptional microbial structure

The influence of different concentrations of fulvic acid at 0, 100, 200, and 400 mg/kg was evaluated during the course of composting with straw and mushroom residues as substrates. The optimal concentration of fulvic acid is 100 mg/Kg based on microbial characteristics, chemical parameters, and germination index testing. Nearly 80% of the microbial taxa responded significantly to fulvic acid over the composting period, with a dynamic change of the co-occurrence network from complex to simple and then to complex. Fulvic acid accelerated the progress of composting and reduced the emission of gases at the thermophilic phase. The optimal concentration of fulvic acid enriched the beneficial microorganisms Aeribacillus, Oceanobacillus, and Rhodospirillaceae, and decreased the abundances of pathogenic microorganisms Corynebacterium, Elizabethkingia, and Sarcocystidae. This study indicates a new strategy to optimize the composting process using the biostimulant fulvic acid.

Fate of antibiotics and antibiotic resistance genes during aerobic co-composting of food waste with sewage sludge

Aerobic composting is widely used on transforming organic solid waste into proliferating products. However, the removal of antibiotics and antibiotic resistance genes (ARGs) in the process of co-composting of food waste with sewage sludge has been rarely reported to date. Therefore, we investigated a laboratory-scale composting using food waste and sewage sludge as substrates to study changes in antibiotics and ARGs during composting. Varying dose of antibiotics were added to allow the evaluation of changes in antibiotics, the microbial community and ARGs. The results revealed that composting effectively removed fluoroquinolones and macrolides, while showed poor efficiency in removing sulfonamides. Results from the 16S rRNA sequencing revealed that Firmicutes dominated on D0, while Proteobacteria and Actinomycetes dominated on D28, and a high concentration of antibiotics affected the microbial succession. The quantitative PCR demonstrated that the abundance of sul3, sulA, qnrB, qnrS, and ermB was reduced after 28 days composting, while an increase in the abundance of sul1, sul2, qnrD, ermC, and ermF was induced by high concentrations of antibiotics. Redundancy analysis revealed that total organic matter was the most important factor for the variation in the ARGs abundance. Overall, our findings indicated that the aerobic co-composting of food waste with sewage sludge can effectively remove antibiotics and ARGs. Our study sheds a new idea light on the strategy for the removal of antibiotics and ARGs from organic solid waste.

Organic matter- and temperature-driven deterministic assembly processes govern bacterial community composition and functionality during manure composting

Although many studies have shown that microbial communities play important roles in organic waste composting due to the involvement of specific microbial taxa with metabolic functions, the underlying ecological processes of community assembly and governing factors remain elusive. Thus, a chicken manure composting experiment as a model system of microbially mediated organic waste composting was conducted. Ecological null modeling and metabolic functional prediction combined with electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to quantify assembly processes governing bacterial community composition and functions during composting. The results showed the predominant role of deterministic assembly processes in shifting community compositions both across and within composting stages. Stochastic assembly processes also concomitantly influenced microbial community compositions. Changes in the organic matter (OM) content and its chemical properties and temperature governed bacterial community assembly processes throughout the stages by selecting specific bacterial taxa such as Cardiobacteriales, Bacteroidales, and Lachnospiraceae on day 1, Firmicutes on days 6, 25 and 37, and Sphingobacteriales, Thermoactinomycetaceae, Actinobacteria, and Novibacillus on day 45. These taxa ultimately influenced community functions such as environmental information processing, carbohydrate and amino acid metabolism, cellular processes, and genetic information processes involved in composting. Taken together, this study indicates that deterministic assembly processes governed by OM content and quality as well as temperature influenced microbial community turnover and determined community functions during composting. These results are important for better understanding and predicting microbial-driven composting and for ultimately manipulating microorganisms for environmentally-friendly composting outcomes.

Enhanced removal of antibiotic resistance genes and mobile genetic elements during swine manure composting inoculated with mature compost

Livestock manure is a major source of antibiotic resistance genes (ARGs) that enter the environment. This study assessed the effects of inoculation with mature compost (MC) on the fates of ARGs and the bacterial community during swine manure composting. The results showed that MC prolonged the thermophilic period and promoted the decomposition of organic matter, which was due to the rapid growth and reproduction of thermophilic bacteria (Bacillus, Thermobifida, and Thermobacillus). MC significantly reduced the relative abundances of ARGs (1.02 logs) and mobile genetic elements (MGEs) (1.70 logs) after composting, especially sulfanilamide resistance genes. The total ARGs removal rate was 1.11 times higher in MC than the control. Redundancy analysis and structural equation modeling showed that horizontal gene transfer mediated by MGEs (ISCR1 and intI1) was the main direct factor related to the changes in ARGs during composting, whereas the C/N ratio and pH were the two most important indirect factors. Network analysis showed that members of Firmicutes comprising Romboutsia, Clostridisensu_stricto_1, and Terrisporobacter were the main bacterial hosts of ARGs and MGEs. MC reduced the risk of ARGs transmission by decreasing the abundances of bacterial hosts. Thus, MC is a promising strategy for reducing the proliferation risk of ARGs.

δ-MnO2 changed the structure of humic-like acid during co-composting of chicken manure and rice straw

Improving the structure and quantity of humus is important to reduce agriculture organic waste by composting. The present study was aimed to assess the role of δ-MnO₂ on humus fractions formation during co-composting of chicken manure and rice straw. Two tests (control group (CK), the addition of δ-MnO₂ (M)) were carried out. The results showed that organic matter content decreased by 34% and 29% at M and CK, suggesting the process of organic waste disposal was accelerated by adding δ-MnO₂. The structures and quantity of fulvic acid (FA) and humic acid (HA) (as the main fractions of humus) were investigated. The δ-MnO₂ had no significant effect on improving the concentration of FA and HA (p > 0.05). However, the addition of δ-MnO₂ caused different effects on the FA and HA structure. The humification degree of FA improved, while bioavailability of HA increased through adding δ-MnO₂. The addition of δ-MnO₂ rephased the bacterial community structure, slowing down the succession rate of the bacterial community in M composting. After adding δ-MnO_2, the structural equation modeling results showed that environmental factors could directly drive changes in FA and HA by modulating the bacterial community. Furthermore, the role of FA and HA in the soil amendment was also demonstrated. Therefore, the addition of MnO₂ might be promising for agriculture organic waste treatment and environmental repair during composting.

Fungal community succession contributes to product maturity during the co-composting of chicken manure and crop residues

The succession of the fungal community during the co-composting of chicken manure and crop residues and its role in relation to compost maturity was deciphered using Illumina sequencing and FUNGuild (Fungi + Functional + Guild) tool. In the maturation phase of composting, the relative abundance of pathogenic and symbiotrophic fungi decreased by 68%-85% and 145%-622%, respectively, as compared to the initial phase, which showed 574%-720% increase in the saprotrophic guild. The pathogenic and saprotrophic fungi abundance was correlated to compost maturity represented by germination index and humic spectroscopic ratio (p < 0.05). Random forest analysis and structural equation modeling elucidated the positive effects of the aforementioned fungal taxa on compost maturity, and these effects were mediated by the micro-environmental variables, such as temperature, NH₄⁺-N/NO₃^--N ratio and total organic carbon content. Our study outlines the importance of fungal community succession for improving composting performance and efficiency.

In situ SERS monitoring of photocatalysts by Au-decorated Fe3O4@TiO2 nanocomposites: novel perspectives and insights

The design and preparation of multifunctional nanomaterials are very important for photocatalytic research.

Cleaner production of agriculturally valuable benignant materials from industry generated bio-wastes: A review

Bio-wastes from different agro-based industries are increasing at a rapid rate with the growing human population's demand for the products. The industries procure raw materials largely from agriculture, finish it with the required major product, and produce huge bio-wastes which are mostly disposed unscientifically. This creates serious environmental problems and loss of resources and nutrients. Traditional bio-wastes disposal possess several demerits which again return with negative impact over the eco-system. Anaerobic digestion, composting, co-composting, and vermicomposting are now-a-days given importance due to the improved and modified methods with enhanced transformation of bio-wastes into suitable soil amendments. The advanced and modified methods like biochar assisted composting and vermicomposting is highlighted with the updated knowledge in the field. Hence, the present study has been carried to compile the effective and efficient methods of utilizing industry generated bio-wastes for circularity between agriculture - industrial sectors to promote sustainability.

Modified montmorillonite and illite adjusted the preference of biotic and abiotic pathways of humus formation during chicken manure composting

The study aimed to identify the preference of pathways of humus formation. Five lab-scale composting experiments were established: the control (CK), montmorillonite addition (M), illite addition (I), thermal treatment montmorillonite addition (M-) and thermal treatment illite addition (I-). Results showed humus content was increased by 11.5%, 39.3%, 37.2%, 30.9% and 27.6% during CK, M-, M, I- and I composting. Meanwhile, Redundancy analysis indicated the bands of bacteria community related to humic acid (HA) were more abundant in the M- and I- treatments. Furthermore, structural equation model and variance partitioning analysis demonstrated that M- and I- treatments promoted precursors to synthesize HA by coordinated regulation of biotic pathway and abiotic pathway, the increase of HA in the M and I treatments mainly through the abiotic pathway. In summary, an effective method was proposed to improve humus production by adjusting the preference of biotic and abiotic pathways of humus formation.