Tracking organic matter and microbiota dynamics during the stages of lignocellulosic waste composting

Rapid in-situ aerobic biodegradation of high salt and oily food waste employing constructed synthetic microbiome

The high salt content of food waste (FW) severely limits microbial physiological activity and reduces its biodegradability. In this study, a salt-tolerant thermophilic bacterial agent that consists of four different substrate degradation functional strains was evaluated for efficient high salt and oily FW in solid-state aerobic biodegradation disposers. The phy-chemical properties, enzyme activities, microbial community structure, and function during the biodegradation process were evaluated under high salt (5%) stress. The results showed that the agent promoted the degradation rate, increased the matrix temperature, decreased the moisture content (MC), and enhanced enzyme activities without putrid smell. High-throughput sequencing indicated community structure succession between different groups and the positive contribution of the inoculated functional strains. During the FW biodegradation process, the Bacillus sp. inoculated was the dominant genus in the agent group. Furthermore, CCA further confirmed the positive effects of the four inoculated strains on high salt and oily FW aerobic biodegradation. Functional prediction and metabolite results both confirmed that the agent was more efficient in carbon, amino acid, and lipid metabolism, which demonstrated that the synthetic microbial consortium holds a potential advantage for efficiency and subsequent resource utilization for organic fertilizer.

Enhanced humification via lignocellulosic pretreatment in remediation of agricultural solid waste

Stover and manure are the main solid waste in agricultural industry. The generation of stover and manure could lead to serious environmental pollution if not handled properly. Composting is the potential greener solution to remediate and reduce agricultural solid waste, through which stover and manure could be remediated and converted into organic fertilizer, but the long composting period and low efficiency of humic substance production are the key constraints in such remediation approach. In this study, we explore the effect of lignocellulose selective removal on composting by performing chemical pretreatment on agricultural waste followed by utilization of biochar to assist in the remediation by co-composting treatment and reveal the impacts of different lignocellulose component on organic fertilizer production. Aiming to discover the key factors that influence humification during composting process and improve the composting quality as well as comprehensive utilization of agricultural solid waste. The results demonstrated that the removal of selective lignin or hemicellulose led to the shift of abundances lignocellulose-degrading bacteria, which in turn accelerated the degradation of lignocellulose by almost 51.2%. The process also facilitated the remediation of organic waste via humification and increased the humic acid level and HA/FA ratio in just 22 days. The richness of media relies on their lignocellulose content, which is negatively correlated with total nitrogen content, humic acid (HA) content, germination index (GI), and pH, but positively correlated with fulvic acid (FA) and total organic carbon (TOC). The work provides a potential cost effective and efficient framework for agricultural solid waste remediation and reduction.

The co-inoculation of Trichoderma viridis and Bacillus subtilis improved the aerobic composting efficiency and degradation of lignocellulose

The aim of this study was to reveal the mechanism by which co-inoculation with both Trichoderma viridis and Bacillus subtilis improved the efficiency of composting and degradation of lignocellulose in agricultural waste. The results showed that co-inoculation with Trichoderma and Bacillus increased abundance of Bacteroidota to promote the maturation 7 days in advance. Galbibacter may be a potential marker of co-inoculation composting efficiency compost. The compost became dark brown, odorless, and had a carbon to nitrogen ratio of 16.40 and a pH of 8.2. Moreover, Actinobacteriota and Firmicutes still dominated the degradation of lignocellulose following inoculation with Trichoderma or Bacillus 35 days after composting. Bacterial function prediction analysis showed that carbohydrate metabolism was the primary metabolic pathway. In conclusion, co-inoculation with Trichoderma and Bacillus shortened the composting cycle and accelerated the degradation of lignocellulose. These findings provide new strategies for the efficient use of agricultural waste to produce organic fertilizers.

Long-term microbial community succession and mechanisms of regulation of dissolved organic matter derivation in livestock manure fermentation system

Industrial-scale aerobic fermentation was conducted with livestock manures. Microbial inoculation promoted the growth of Bacillaceae and consolidated its position as the dominant microorganism. Microbial inoculation substantially influenced dissolved organic matter (DOM) derivation and variations of related components in the fermentation system. The relative abundance of humic acid-like substances of DOM increased from 52.19% to 78.27% in microbial inoculation system, resulting in a high humification level. Moreover, lignocellulose degradation and microbial utilization were the important factors influencing DOM content in fermentation systems. The fermentation system was regulated by microbial inoculation, thus achieving a high level of fermentation maturity.

Effect of calcium peroxide assisted microwave irradiation pretreatment on humus formation and microbial community in straw and dairy manure composting

In this study, the effects of four pretreatment methods on the crystallinity of maize straw were compared, and the CaO₂ assisted microwave pretreatment was selected for straw and dairy manure composting. The humification and microbial community were investigated. Results showed that the pretreatment increased the initial water-soluble carbon, which favored the microbial activity, and the CO₂ release increased by 15.71%. Pretreatment promoted the lignocellulose degradation, with total degradation ratio of 37.06%. The final humic acid content was 11.39 g/kg higher than the control. Spearman correlation analysis indicated that polyphenols and amino acids were significantly related to humus formation. In addition, pretreatment rendered the Firmicutes the most dominant phylum, and increased the metabolic intensity of reducing sugar metabolism, aromatic amino acid biosynthesis and carbon fixation pathways. Redundancy analysis revealed that the dominant genus of Firmicutes was significantly positively correlated with humus, while that of Actinobacteriota was correlated with CO₂ release.

Diversity of lignocellulolytic functional genes and heterogeneity of thermophilic microbes during different wastes composting

The goal of this study was to investigate the heterogeneity of thermophilic microorganisms and their lignocellulose-degrading gene diversity during composting. In this study, bagasse pith/dairy manure (BAG) and sawdust/dairy manure (SAW) were used as experimental subjects. The pour plate method indicated that thermophilic bacteria and thermophilic actinobacteria were more culturable than thermophilic fungi. Metagenomics analysis showed that the Actinobacteria, Firmicutes and Proteobacteria were the dominant phyla during composting. In addition, auxiliary activity and glycoside hydrolase families were critical for lignocellulosic degradation, which were found to be more abundant in BAG. As a result, the degradation rates of cellulose, hemicellulose and lignin in BAG (7.36%, 13.99% and 5.68%) were observably higher than those in SAW (6.13%, 12.09% and 2.62%). These findings contribute to understanding how thermophilic microbial communities play a role in the deconstruction of different lignocelluloses and provide a potential strategy to comprehensively utilize the resources of lignocellulosic biomass.

Decomposition and humification process of domestic biodegradable waste by black soldier fly (Hermetia illucens L.) larvae from the perspective of dissolved organic matter

Black soldier fly larvae (Hermitia illucens L.) (BSFL) bioconversion is a promising technology for domestic biodegradable waste (DBW) management and resource recovery. However, little is known about the DBW biodegradation during the BSFL bioconversion from the perspective of dissolved organic matter (DOM). In the current study, field tests were conducted on a full-scale BSFL bioconversion facility with treatment capacity of 15 tons DBW/day. Composition of DOM in DBW were investigated by spectral analysis (UV-vis, fluorescence, and Fourier Transform Infrared spectroscopy (FT-IR)), coupled with enzyme activity analysis. After BSFL bioconversion, DOM concentrations, total carbon and total nitrogen in residues decreased by 51.5%, 18.3% and 19.9%, respectively. Meanwhile, enzymes like catalase, lipase, protease, sucrase, urease and cellulase significantly increased (9.28%-56.3%). The specific UV absorbance at 254 nm and 280 nm (SUVA₂₅₄, SUVA₂₈₀), the area at 226-400 nm (A_226-400) and slope in the 280-400 nm region (S_280-400) of DOM increased by 230%, 186%, 143% and 398%, respectively. Moreover, the characteristic peaks at 1636, 1077 and 1045 cm^-1 in FT-IR increased continuously, with a significant decrease in peak at 1124 and 1572 cm^-1. DOM spectral data show that BSFL decomposed the carboxylic, cellulose and aliphatic components, resulting in the increase of oxygen-containing functional groups (e.g., hydroxyl, carboxyl, carbonyl) and aromatic compounds. Furthermore, fluorescence profiles show that Region Ⅰ, Ⅱ (aromatic proteins) and Ⅳ (soluble microbial byproducts) decreased while Region Ⅴ (humic-like substances) increased significantly. Humification index increased by 122% while biological index decreased by 18.0%, indicating a significant increase in degree of humification and stabilization of the residues. The current evidence provides a theoretical basis for technical re-innovation and improving economic potential of BSFL technology.

Diversity and enzymatic activity of the microbiota isolated from compost based on restaurant waste and yard trimmings

Introduction

The bad management of organic waste negatively affects environmental quality and composting has been a viable recycling alternative. Microorganisms are responsible for waste degradation during the composting process and, consequently, for transforming this waste into natural fertilizer. This work aimed to analyze and identify the biodiversity of yeasts and filamentous fungi throughout a composting process based on organic residues under different treatments (commercial inoculum, non-commercial inoculum, and control treatment) and to investigate the enzymatic activity of these microorganisms.

Methods

Microorganisms were isolated and identified from samples at 0, 5, 10, 20, 40, 60, and 120 days. Filamentous fungi were identified according to their macroscopic and microscopic characteristics, and yeasts were identified by sequencing the 18S rDNA region. All identified strains were evaluated for ligninolytic, cellulolytic, hemicellulolytic, amylolytic, pectinolytic, proteolytic, lipolytic, and ammonification. During the composting phases, the filamentous fungi were higher than the yeast population.

Results and discussion

At the beginning of the process, a higher species diversity was observed, and the population of yeasts and filamentous fungi was, on average, 6.50 log CFU g−1. The microbial communities were similar throughout the process in the two inoculated treatments, which showed more significant microbial activity, diversity, and efficiency in the transformation of organic matter, and consequently, advantages in terms of the final product quality compared to the control treatment. The yeasts Pichia kudriavzevii, Pichia farinosa, Issatchenkia orientalis, and the filamentous fungi of the genus Aspergillus spp. proved to have high biotechnological value and could be used as starter cultures to accelerate the composting process.

Quinone redox cycling drives lignocellulose depolymerization and degradation in composting environments based on metagenomics analysis

In this study, the effect of Fe³⁺ on the quinone redox cycling driving lignocellulosic degradation in composting systems was investigated. The results showed that the degradation rates of cellulose, hemicellulose, and lignin were higher in the experimental group (CT) with Fe₂(SO₄)₃ addition than in the blank group (CK) (CT, 52.55 %, 45.14 %, 56.98 %; CK, 49.63 %, 37.34 %, 52.3 %). Changes in the abundance of key enzymes for quinone reduction (AA3_1, AA3_2, AA6) and the structural succession of microbial communities were analyzed by metagenomic analysis. Among them, Fe₂(SO₄)₃ had the most significant effect on AA3_2, with an approximately 8-fold increase in abundance compared to the beginning of composting. The dominant phylum in the composting process was Actinobacteria. In conclusion, the addition of Fe₂(SO₄)₃ contributed to the quinone redox cycling and effectively improved the degradation rate of lignocellulose in composting.

Dynamics of bacterial and archaeal communities during horse bedding and green waste composting

Organic waste decomposition can make up substantial amounts of municipal greenhouse emissions during decomposition. Composting has the potential to reduce these emissions as well as generate sustainable fertilizer. However, our understanding of how complex microbial communities change to drive the chemical and biological processes of composting is still limited. To investigate the microbiota associated with organic waste decomposition, initial composting feedstock (Litter), three composting windrows of 1.5 months (Young phase), 3 months (Middle phase) and 12 months (Aged phase) old, and 24-month-old mature Compost were sampled to assess physicochemical properties, plant cell wall composition and the microbial community using 16S rRNA gene amplification. A total of 2,612 Exact Sequence Variants (ESVs) included 517 annotated as putative species and 694 as genera which together captured 57.7% of the 3,133,873 sequences, with the most abundant species being Thermobifida fusca, Thermomonospora chromogena and Thermobifida bifida. Compost properties changed rapidly over time alongside the diversity of the compost community, which increased as composting progressed, and multivariate analysis indicated significant variation in community composition between each time-point. The abundance of bacteria in the feedstock is strongly correlated with the presence of organic matter and the abundance of plant cell wall components. Temperature and pH are the most strongly correlated parameters with bacterial abundance in the thermophilic and cooling phases/mature compost respectively. Differential abundance analysis revealed 810 ESVs annotated as species significantly varied in relative abundance between Litter and Young phase, 653 between the Young and Middle phases, 1182 between Middle and Aged phases and 663 between Aged phase and mature Compost. These changes indicated that structural carbohydrates and lignin degrading species were abundant at the beginning of the thermophilic phase, especially members of the Firmicute and Actinobacteria phyla. A high diversity of species capable of putative ammonification and denitrification were consistently found throughout the composting phases, whereas a limited number of nitrifying bacteria were identified and were significantly enriched within the later mesophilic composting phases. High microbial community resolution also revealed unexpected species which could be beneficial for agricultural soils enriched with mature compost or for the deployment of environmental and plant biotechnologies. Understanding the dynamics of these microbial communities could lead to improved waste management strategies and the development of input-specific composting protocols to optimize carbon and nitrogen transformation and promote a diverse and functional microflora in mature compost.

Recent advances in metagenomic analysis of different ecological niches for enhanced biodegradation of recalcitrant lignocellulosic biomass

Lignocellulose wastes stemming from agricultural residues can offer an excellent opportunity as alternative energy solutions in addition to fossil fuels. Besides, the unrestrained burning of agricultural residues can lead to the destruction of the soil microflora and associated soil sterilization. However, the difficulties associated with the biodegradation of lignocellulose biomasses remain as a formidable challenge for their sustainable management. In this respect, metagenomics can be used as an effective option to resolve such dilemma because of its potential as the next generation sequencing technology and bioinformatics tools to harness novel microbial consortia from diverse environments (e.g., soil, alpine forests, and hypersaline/acidic/hot sulfur springs). In light of the challenges associated with the bulk-scale biodegradation of lignocellulose-rich agricultural residues, this review is organized to help delineate the fundamental aspects of metagenomics towards the assessment of the microbial consortia and novel molecules (such as biocatalysts) which are otherwise unidentifiable by conventional laboratory culturing techniques. The discussion is extended further to highlight the recent advancements (e.g., from 2011 to 2022) in metagenomic approaches for the isolation and purification of lignocellulolytic microbes from different ecosystems along with the technical challenges and prospects associated with their wide implementation and scale-up. This review should thus be one of the first comprehensive reports on the metagenomics-based analysis of different environmental samples for the isolation and purification of lignocellulose degrading enzymes.

Dynamics of microbiota and physicochemical characterization of food waste in a new type of composter

Organic wastes are considered the most significant components of urban solid waste, negatively affecting the environment. It is essential to use renewable resources to minimize environmental risks. Composting is one of the most sustainable methods for managing organic waste and involves transforming organic matter into a stable and nutrient-enriched biofertilizer, through the succession of microbial populations into a stabilized product. This work aimed to evaluate the efficiency of the new type of composter and the microbial and physiochemical dynamics during composting aiming to accelerate the degradation of organic waste and produce high-quality compost. Two inoculants were evaluated: (1) efficient microorganisms (EM); (2) commercial inoculum (CI), which were compared to a control treatment, without inoculation. Composting was performed by mixing organic waste from gardening with residues from the University's Restaurant (C/N ratio 30:1). The composting process was carried out in a 1 m3 composter with controlled temperature and aeration. The thermophilic phase for all treatments was reached on the second day. Mature compost was obtained after an average of 120 days, and composting in all treatments showed an increase in the availability of P and micronutrients. The new composter helped to accelerate the decomposition of residues, through the maintenance of adequate oxygen content and temperature control inside the cells, providing high metabolic activity of microorganisms, contributing to an increase in physicochemical characteristics, also reducing the composting time in both treatments. During composting, the bacteria and actinobacteria populations were higher than yeasts and filamentous fungi. The inoculated treatments presented advantages showing more significant mineralization of P-available and micronutrients such as Mn and Zn in terms of the quality of the final product in comparison to the control treatment. Finally, the new composter and the addition of inoculants contributed significantly to the efficiency of the process of composting organic waste.

Lignocellulosic depolymerization induced by ionic liquids regulating composting habitats based on metagenomics analysis

The application of ionic liquids with sawdust and fresh dairy manure was studied in composting. The degradation of organic matter (OM), dissolved organic matter (DOM), and lignocellulose was analyzed. The DOM decreased by 14.25 mg/g and 11.11 mg/g in experimental group (ILs) and control group (CK), respectively. OM decreased by 7.32% (CK) and 8.91% (ILs), respectively. The degradation rates of hemicellulose, lignin, and cellulose in ILs (56.62%, 42.01%, and 23.97%) were higher than in CK (38.39%, 39.82%, and 16.04%). Microbial community and carbohydrate-active enzymes (CAZymes) were analyzed based on metagenomics. Metagenomic analysis results showed that ionic liquids enriched Actinobacteria and Proteobacteria in composting. Compared with CK, the total abundance values of GH11, GH6, AA6, and AA3_2 in ILs increased by 13.98%, 10.12%, 11.21%, and 13.68%, respectively. Ionic liquids can improve the lignocellulosic degradation by regulating the environmental physicochemical parameters (temperature, pH, C/N) to promote the growth of Actinobacteria and Proteobacteria and carbohydrate-active enzymes (CAZymes) abundance. Therefore, ionic liquids are a promising additive in lignocellulosic waste composting.

In-situ generation of H2O2 by zero valent iron to control depolymerization of lignocellulose in composting niche

Lignocellulosic degradation is a bottleneck of bioconversion during the composting process. In-situ generation of H₂O₂ in the composting system was an ideal method for efficiently promoting lignocellulase degradation, and zero valent iron (ZVI) was concerned because it can generate H₂O₂ by reducing dissolved oxygen. This study focused on the effects of ZVI treatment on lignocellulose degradation, microbial communities, and carbohydrate-active enzymes (CAZymes) genes during composting. Its results indicated that ZVI increased H₂O₂ content during composting, accompanied by the formation of •OH. The degradation rates of lignin, cellulose and hemicellulose in ZVI group (20.77%, 30.35% and 44.7%) were significantly higher than in CK group (17.01%, 26.12% and 38.5%). Metagenomic analysis showed that ZVI induced microbial growth that favored lignocellulose degradation, which increased the abundance of Actinobacteria and Firmicutes but reduced Proteobacteria. At the genus level, the abundance of Thermomonospora, Streptomyces, and Bacillus significantly increased. In addition, glycoside hydrolases and auxiliary activities were important CAZymes families of lignocellulose degradation, and their abundance was higher in the ZVI group. Redundancy analysis showed that the increased H₂O₂ and •OH content was a critical factor in improving lignocellulose degradation. Overall, H₂O₂ as a co-substrate enhanced the enzymatic efficiency, •OH unspecifically attacked lignocellulose, and the increase in functional microbial abundance was the main reason for promoting lignocellulose degradation in composting.

Interval aeration improves degradation and humification by enhancing microbial interactions in the composting process

Five full-scale food waste composts were conducted under different aeration frequencies (no aeration, aeration at different intervals, and continuous aeration) to reveal the optimal strategy and its microbial mechanisms. The highest degradation rate (77.2%) and humus content (29.3%) were observed in Treatment D with interval aeration (aeration 20 min, pause 10 min). Aeration influenced the degradation and humification rate by regulating microbial interactions. The microbial interactions peaked in Treatment D, with a 1.30-fold increase. In terms of the microbial community, Thermobifida was a key genus for improving positive cohesion, fulfilling three criteria (high abundance, high occurrence frequency, and significant differences between treatments). The aeration strategy employed in Treatment D not only increased relative abundance of Thermobifida (1.2 times higher) but also strengthened interaction between it and functional genera (34 nodes). Overall, interval aeration, featured by 20 min aeration and 10 min pause, could increase microbial interactions and improve composting efficiency.

Pretreatment of rice straw by newly isolated fungal consortium enhanced lignocellulose degradation and humification during composting

The slow decomposition rate of the reluctant structure of lignocellulose in agricultural waste is the great limitation of composting processes, which can be averted by pretreatment-strategies. This study focused on the impacts of pretreating rice straw using a consortium of newly isolated fungal species on lignocellulose degradation and humic substances during composting. Fungal pretreatment had a significant impact on lignocellulose degradation (84%) of rice straw by producing higher lignocellulytic enzymes than chemical pretreatments (79%) or the control (61%). The compost with fungal pretreated rice straw (FPT) showed significantly high composting temperature in the late mesophilic stage, which enhanced the degradation of lignocellulose. The fluorescence excitation emission spectroscopy revealed that significantly more humic acid-like compounds were formed in FPT. These findings suggest that fungal pretreatment is a feasible method to accelerate straw degradation and humification.

Effects of Vermicompost Substrates and Coconut Fibers Used against the Background of Various Biofertilizers on the Yields of Cucumis melo L. and Solanum lycopersicum L

Vermicompost has been promoted as a viable substrate component owing to its physicochemical properties, nutrient richness, and status as an excellent soil improver. It is considered the best organic fertilizer and is more eco-friendly than chemical fertilizers. Plant-growth-promoting microorganisms (PGPMs) are defined as plant biofertilizers that improve nutritional efficiency—that is, they transform nutrients within substrates from organic to inorganic forms, making them available for plants. The main objective of this research study is to evaluate the effects of the application of three PGPM microbial consortia on different mixtures of organic substrates based on vermicompost (V) and coconut fiber (CF) on two different horticultural crops. We performed a yield analysis and drainage nutrient tests and determined the plant nutritional status and enzymatic activity in organic substrates based on the two crops, Cucumis melo L. and Solanum lycopersicum L. A multivariate analysis of variance and principal component analysis was conducted using substrate types and PGPMs as factors. Differences (p < 0.05) in yield, dehydrogenase activity, the nutrient concentrations in a petiole sap, and drainage were observed at 30, 60, 75, and 90 days after transplant. PGPMs such as Trichoderma sp. and plant-growth-promoting rhizobacteria (PGPR) in organic substrates (40V + 60CF) can significantly improve the nutritional status of plants for use in organic soilless container agriculture. Biofertilization with PGPMs and suitable mixtures of organic substrates together with aqueous extracts (tea) of vermicompost, as nutrient solutions applied by fertigation, has allowed us to achieve an adequate level of production through environmentally friendly techniques. The results obtained allowed us to affirm that it was possible to replace conventional fertilization using chemical products and ensure adequate crop nutrition by supplying the main macronutrients.

Insights on dissolved organic matter and bacterial community succession during secondary composting in residue after black soldier fly larvae (Hermetia illucens L.) bioconversion for food waste treatment

Black soldier fly larvae (Hermetia illucens L. BSFL) bioconversion is a promising biotechnology for food waste treatment. However, the separated residues still do not meet criteria for use as land application biofertilizers. In this work, we investigated a full-scale BSFL bioconversion project to explore features of dissolved organic matter (DOM) and its associated responses of bacterial community succession in residue during secondary composting. Data showed that the concentrations of total nitrogen and ammonium nitrogen decreased by 11.8% and 22.6% during the secondary composting, respectively, while the nitrate nitrogen concentration increased 18.7 times. The DOM concentration decreased by 69.1%, in which protein-like, alcohol-phenol, and biodegradable aliphatic substances were metabolized by bacteria during the thermophilic phase together with the accumulation of humus-like substances, resulting in an increase in the relative concentration of aromatic compounds. The structure of the bacterial community varied at different stages of the bioprocess, in which Bacteroidetes, Actinobacteria, Proteobacteria, and Firmicutes were the dominant bacterial phyla. Lysinibacillus, Pusillimonas, and Caldicoprobacter were found to be key contributors in the degradation and formation of DOM. The DOM concentration (33.4%) and temperature (17.7%) were the prime environmental factors that promoted succession of the bacterial community. Through bacterial metabolism, the structural stability of DOM components was improved during the composting process, and the degrees of humification and aromaticity were also increased. This study depicted the dynamic features of DOM and the associated bacterial community succession in residue during secondary composting, which is conducive with the reuse of BSFL residue as biofertilizer for agriculture.

Cultivating Lentinula edodes on Substrate Containing Composted Sawdust Affects the Expression of Carbohydrate and Aromatic Amino Acid Metabolism-Related Genes

In mushroom cultivation, composting the substrate can make the nutrients more easily absorbed by hyphae due to the degradation of lignin, cellulose, and other organic matter. However, the effects of cultivating Lentinula edodes on composted substrate and the related molecular mechanisms have not been studied systemically. We applied transcriptomics, qRT-PCR, and proteomics to study L. edodes cultivated on substrates with fresh (CK) and composted (ND) sawdust, focusing on the brown film formation stage. The time of brown film formation was shorter and the mycelium growth rate and crude polysaccharide content of the brown film were higher in ND than in CK. The faster growth rate in ND may have been due to the higher nitrogen content in ND than in CK. Among the 9,455 genes annotated using transcriptomics, 96 were upregulated and 139 downregulated in ND compared with CK. Among the 2,509 proteins identified using proteomics sequencing, 74 were upregulated and 113 downregulated. In the KEGG pathway analyses, both differentially expressed genes and proteins were detected in cyanoamino acid metabolism, inositol phosphate metabolism, pentose and glucuronate interconversions, phosphatidylinositol signaling system, RNA polymerase, starch and sucrose metabolism, and tyrosine metabolism pathways. A large number of differentially expressed genes (DEGs) related to aromatic amino acid metabolic and biosynthetic process were upregulated in ND. Most of the DEGs annotated to carbohydrate active enzymes were downregulated in L. edodes growing on composted sawdust containing substrate, possibly due to the lower hemicellulose and cellulose contents in the composted sawdust. The results suggested that using composted substrate may decrease the cultivation time and improve the quality of L. edodes and revealed the underlying molecular mechanisms. IMPORTANCE Composted substrates are not commonly used in the cultivation of Lentinula edodes, thus the effects of cultivating L. edodes on composted substrate and the related molecular mechanisms have not been studied systemically. We studied L. edodes cultivated on substrates with fresh (CK) and composted (ND) sawdust, focusing on the brown film formation stage, and determined the composting related differences in the substrate and in the growth and gene expression of L. edodes. Cultivation on composted substrate was beneficial and showed potential for decreasing the cultivation time and improving the quality of L. edodes. Analyzing the expression levels of genes and proteins in brown film revealed gene and metabolism pathway level changes that accompanied the cultivation on composted substrate.

Food waste composting based on patented compost bins: Carbon dioxide and nitrous oxide emissions and the denitrifying community analysis

Mature compost and rice bran were used as bulking agents to perform Food Waste Rapid Composting (FWRC) in a patented composting bin. The characteristics of CO₂ and N₂O emission and the denitrifying community were investigated. The release of CO₂ and N₂O concentrated in the early composting stage and reduced greatly after 28 h, and the N₂O emission peak of the treatment with mature compost was 8.5 times higher than that of rice bran. The high N₂O generation resulted from massive denitrifying bacteria and NO_x^--N in the composting material. The relative abundances of denitrifiers, correspondingly genes of narG and nirK were much higher in the treatment with mature compost, which contributed to the N₂O emission. Moreover, the correlation matrices revealed that N₂O fluxes correlated well with moisture, pH, temperature, and the abundances of nirK and nosZ genes during FWRC.

Lytic polysaccharide monooxygenases (LPMOs) producing microbes: A novel approach for rapid recycling of agricultural wastes

Out of the huge quantity of agricultural wastes produced globally, rice straw is one of the most abundant ligno-cellulosic waste. For efficient utilization of these wastes, several cost-effective biological processes are available. The practice of field level in-situ or ex-situ decomposition of rice straw is having less degree of adoption due to its poor decomposition ability within a short time span between rice harvest and sowing of the next crop. Agricultural wastes including rice straw are in general utilized by using lignocellulose degrading microbes for industrial metabolite or compost production. However, bioconversion of crystalline cellulose and lignin present in the waste, into simple molecules is a challenging task. To resolve this issue, researchers have identified a novel new generation microbial enzyme i.e., lytic polysaccharide monooxygenases (LPMOs) and reported that the combination of LPMOs with other glycolytic enzymes are found efficient. This review explains the progress made in LPMOs and their role in lignocellulose bioconversion and the possibility of exploring LPMOs producers for rapid decomposition of agricultural wastes. Also, it provides insights to identify the knowledge gaps in improving the potential of the existing ligno-cellulolytic microbial consortium for efficient utilization of agricultural wastes at industrial and field levels.

Impact of inoculation and turning for full-scale composting on core bacterial community and their co-occurrence compared by network analysis

Window composting with inoculation or frequent turning is a superior way to improve traditional composting efficiency. However, the relationship between the innocent treatment in composting with inoculation or turning and microbial dynamics is unclear. Here, the impact of inoculation and turning for full scale composting on core bacterial community and their co-occurrence network as well as harmless level were compared by network analysis. Results showed that composts with both inoculation and turning had 46% increase of total organic carbon degradation compared to traditional composting and decreased the abundance of potential pathogens. The relative abundance of thermophilic bacteria and Galbibacter, Methylocaldum, Steroidobacter, etc. increased during composting with turning and inoculation. Luteimonas, Sphaerobacter, Turicibacter and Flavobacterium as core bacteria had significant difference between control and composting with enhanced innocent treatment efficiency. Network analysis suggested that turning increased the number of indigenous core bacteria and inoculation enhanced the interaction among key bacterial network.

Poplar Sawdust Stack Self-Heating Properties and Variations of Internal Microbial Communities

The heat accumulation generated by microbial metabolic activities during the storage of the sawdust may lead to spontaneous combustion accidents. This paper studied the Critical Ambient Temperature (CAT) variation of poplar sawdust at different stack dimensions and investigated the physicochemical properties as well as microbial community dynamics during the self-heating process of poplar sawdust stacks. From the self-heating substances test experiments and Frank-Kamenetskii (FK) theory, it was found that the CAT of poplar sawdust stacks would decrease from 158.27 °C to 102.46 °C with the increase of stack size from 0.1 m to 3.2 m. From the sawdust stack self-heating experiments, microbial metabolic activities were enhanced with the increasing moisture content (by watering) and oxygen (by turning over), which led to a remarkable increase of the sawdust stack temperature and the rapid decomposition of biochemical components (especially cellulose and hemicellulose). From the microbiological community analysis, at the thermophilic stage (around 60 °C, large amounts of heat release in compost bin), the existence of thermostable bacteria (such as Brevibacillus thermoruber, Bacillus thermoamylovorans and Paenibacillus barengoltzii belonging to Firmicutes) played an important role in degrading organic substances. The heat generated by the microbial metabolic activities might lead to spontaneous combustion eventually if sawdust stack is large enough. Therefore, the sawdust should be stacked in a cool and dry area while avoiding large amounts of storage in high humidity environments.

Diverse thermophilic Bacillus species with multiple biotechnological activities are associated within the Egyptian soil and compost samples

Thermophilic strains of Bacillus can express enzymes of higher thermal stability, which allows carrying out industrial fermentations under higher temperatures. This lowers the contamination potential, accelerates mixing rates and facilitates the recovery of fermentation end products. The present study was thus designed to isolate and characterize thermophilic Bacillus cultures from soil and compost samples. Forty-two thermophilic Bacillus isolates could be identified employing morphological, physiological and the 16S rRNA gene sequencing analyses. The isolates showed a high degree of biological diversity involving 13 Bacillus species and 1 subspecies but were dominated by Bacillus licheniformis. Phylogenetic analysis of B. licheniformis isolates based on the DNA sequencing of gyrA and rpoB genes presented them in two main genetic groups. Isolates of five thermophilic species including B. licheniformis, Bacillus altitudinis, Bacillus paralicheniformis, Bacillus subtilis and Bacillus thermoamylovorans showed multiple activities to degrade all of cellulose, hemicellulose and lignin. Those multifunctional thermophilic Bacillus isolates can be harnessed in the degradation of plant wastes for the production of biofuels and compost.

Increased enzyme activities and fungal degraders by Gloeophyllum trabeum inoculation improve lignocellulose degradation efficiency during manure-straw composting

The present study investigated the effect of brown-rot fungus Gloeophyllum trabeum inoculation on lignocellulose degradation, enzyme activities and fungal community during co-composting of swine manure and wheat straw. G. trabeum inoculation shortened the maturation period of composting from 39 to 30 days. Composting piles inoculated with G. trabeum showed a higher degree of maturity as indicated by 31.6% lower C/N ratio and 29.4% higher GI. The decomposition rate of cellulose, hemicellulose and lignin was increased by 181.1%, 49.4% and 109.4%, respectively, due to higher activities of filter paper enzyme, xylanase, manganese peroxidase and laccase. Redundancy analysis showed that inoculating G. trabeum influenced the succession of fungal communities by changing the main physicochemical parameters, resulting in the increased relative abundance of Aspergillus, Mycothermus and Melanocarpus. Pearson correlation analysis indicated that more dominant fungal genera were involved in the production of lignocellulose-degrading enzymes after G. trabeum inoculation.

Co-composting of cotton residues with olive mill wastewater: process monitoring and evaluation of the diversity of culturable microbial populations

With the aim to recommend an integrated alternative for the combined treatment of olive mill wastewater (OMW) and cotton residues (CR), and the production of high value and environmentally friendly products, two compost piles were set up. The first pile (control, pile 1) consisted of ginned CR, whereas the second (pile 2) was made of CR with the addition of OMW. A series of physicochemical parameters and the culturable microbial diversity in both piles were assessed. Co-composting (pile 2) displayed higher temperatures during the whole process, a prolonged second thermophilic phase and temperature values higher than 40 °C even after the thermophilic stage. Comparing the physicochemical parameters of the pile 2 with those of the pile 1, it was deduced that pH in the former was more acidic during the onset of the process; the EC values were higher throughout the process, while the levels of ammonium and nitrate nitrogen, as well as the NH₄⁺/NO₃^- ratios, were lower at most of the sampling dates. By evaluating the abovementioned results, it was estimated that the co-composting process headed sooner toward stability and maturity, Isolated microorganisms from both piles were identified as members of the genera Brevibacillus, Serratia, Klebsiella, and Aspergillus, whereas active thermotolerant diazotrophs were detected in both piles at the 2nd thermophilic phase emerging a promising prospect upon further evaluation for enhancing the end-product quality. Our findings indicate that co-composting is an interesting approach for the exploitation of large quantities of agro-industrial residues with a final product suitable for improving soil fertility and health.

Characterization of Thermophilic Lignocellulolytic Microorganisms in Composting

Composting involves the selection of a microbiota capable of resisting the high temperatures generated during the process and degrading the lignocellulose. A deep understanding of the thermophilic microbial community involved in such biotransformation is valuable to improve composting efficiency and to provide thermostable biomass-degrading enzymes for biorefinery. This study investigated the lignocellulose-degrading thermophilic microbial culturome at all the stages of plant waste composting, focusing on the dynamics, enzymes, and thermotolerance of each member of such a community. The results revealed that 58% of holocellulose (cellulose plus hemicellulose) and 7% of lignin were degraded at the end of composting. The whole fungal thermophilic population exhibited lignocellulose-degrading activity, whereas roughly 8-10% of thermophilic bacteria had this trait, although exclusively for hemicellulose degradation (xylan-degrading). Because of the prevalence of both groups, their enzymatic activity, and the wide spectrum of thermotolerance, they play a key role in the breakdown of hemicellulose during the entire process, whereas the degradation of cellulose and lignin is restricted to the activity of a few thermophilic fungi that persists at the end of the process. The xylanolytic bacterial isolates (159 strains) included mostly members of Firmicutes (96%) as well as a few representatives of Actinobacteria (2%) and Proteobacteria (2%). The most prevalent species were Bacillus licheniformis and Aeribacillus pallidus. Thermophilic fungi (27 strains) comprised only four species, namely Thermomyces lanuginosus, Talaromyces thermophilus, Aspergillus fumigatus, and Gibellulopsis nigrescens, of whom A. fumigatus and T. lanuginosus dominated. Several strains of the same species evolved distinctly at the stages of composting showing phenotypes with different thermotolerance and new enzyme expression, even not previously described for the species, as a response to the changing composting environment. Strains of Bacillus thermoamylovorans, Geobacillus thermodenitrificans, T. lanuginosus, and A. fumigatus exhibiting considerable enzyme activities were selected as potential candidates for the production of thermozymes. This study lays a foundation to further investigate the mechanisms of adaptation and acquisition of new traits among thermophilic lignocellulolytic microorganisms during composting as well as their potential utility in biotechnological processing.

Quantifying the effects of co-composting organic biomass mixtures with inorganic amendments to obtain value-added bio-products

Co-digestion of organic biomass mixed with inorganic amendments could have an impact on composting dynamics. Various studies highlighted fertilizers' role as an additive to lesser the nitrogen loss, while some studies focused on the addition of fertilizers to enhance the efficiency. The changes in carbon, nitrogen components, and humic substances during the organic-inorganic co-compost process were seldom studied. Clarifying these changes might help improve the production process and compost nutrients contents. Thus, this study's purpose is to investigate the effects of inorganic amendments on compost characteristics, compost temperature, biochemical methane production (BMP), and nutritional contents. The inorganic phosphorous (P), sulfur (S), and sulfur solubilizing agent (SSA) were added to Farmyard manure (FYM) mixed with biodegradable waste (BW), including wheat straw, corn stalks, and green lawn waste. The P and S amended treatments were carried out into two sets, with and without SSA. The mixed feedstocks were added in the insulated RBC composting pit (15 x 15 x 10 feet). The compost material's moisture content was maintained 50-65% during the entire composting process for optimum waste digestion i.e., the moisture content (MC) of FYM was 82.7% and for BW ranged 8.8-10.2%, while the C/N ratio was found 10.5 for FYM, 74.5 for wheat straw, 83.5 for corn stalks, and 84.8 for lawn waste. At the condition of compost maturity, the inorganic amendments have no significant effect on composted material's moisture content. The maximum organic matter of 69.7% and C/N ratio of 44.6 was measured in T1. On the 6th day of composting, the temperature reached to thermophilic range (>45 oC) in all the treatments due to aeration of compost increased microbial activities and waste decomposition rate and decreased gradually to mesophilic range (35-45 oC) because the supply of high-energy compounds becomes exhausted. The highest temperature was reached in T4 (58 oC) and lowest in CT (47 oC). The significantly maximum methane of 8.95 m3 and biogas burning was 818 minutes in CT, followed by T1 and T4. The results of this study revealed that P enriched compost is a feasible and sustainable way to overcome P deficiency in the soil as well as in plants and best way to use low-grade P and organic waste material.

Succession of the microbial communities and function prediction during short-term peach sawdust-based composting

Short-term composting of raw materials for preparing oyster mushroom cultivation media is widely used in China, and its microbial mechanism needs to be further studied. 11-days' peach sawdust-based composting was performed to evaluate material conversion and microbial succession using physicochemical analysis and 16S rRNA and ITS sequencing. Composting bacteria demonstrated much higher abundance than fungi. Firmicutes, Actinobacteriota, and Proteobacteria were the dominant bacterial phyla, while most of fungal species belonged to Ascomycota. Moisture was the key factor at the beginning, while total nitrogen, temperature, and lignin became main influencing factors for composting maturity. Actinobacteriota, Firmicutes, and Proteobacteria of bacterial phyla, Eurotiomycetes and Sordariomycetes of fungal classes involved in lignocellulosic degradation. Bacterial function prediction analysis showed that carbohydrate metabolism and amino acid metabolism were the main metabolic pathways. These results confer a better understanding of material and microbial succession during short-term composting and also provide valuable utilization in mushroom industry.

Revisiting the succession of microbial populations throughout composting: A matter of thermotolerance

Composting has been traditionally considered a process in which a succession of mesophilic and thermophilic microbial populations occurs due to temperature changes. In order to deepen in this model, 1380 bacterial and fungal strains (the entire culturable microbiota isolated from a composting process) were investigated for their ability to grow across a wide range of temperatures (20 to 60 °C). First, qualitative tests were performed to establish a thermal profile for each strain. Then, quantitative tests allowed ascertaining the extent of growth for each strain at each of the tested temperatures. The identity of the isolates enabled to position them taxonomically and permitted tracking the strains throughout the process. Results showed that 90% of the isolates were classified as thermotolerant (they grew at all tested temperatures). Only 9% and 1% of the studied strains showed to be strictly mesophilic or thermophilic, respectively. Firmicutes exhibited the greatest thermal plasticity, followed by Actinobacteria and Ascomycota. Most of the Proteobacteria and all Basidiomycota strains were also able to grow at all the assayed temperatures. Thermotolerance was clearly demonstrated among the composting microbiota, suggesting that the idea of the succession of mesophilic and thermophilic populations throughout the process might need a reassessment.

Manipulation of composting oxygen supply to facilitate dissolved organic matter (DOM) accumulation which can enhance maize growth

Promotion of crop yield by compost application is generally thought to be ascribed to a better supply of macro and micronutrients, however the importance of compost DOM on plant growth has not been well demonstrated. In this study, composting of chicken manure, spent mushroom and sawdust was conducted under aerobic or anaerobic condition to determine the effects of compost DOM on plant growth. It was found that dissolved organic matter (DOM) first increased and then decreased in compost, and DOM of anaerobic compost was slightly higher than that of aerobic compost. When compost extract was applied to maize, among N, P, K and DOM content, it was DOM content that was most significantly and strongly related to plant biomass (r = 0.843, p＜0.001). Compost DOM was also strongly related to soil properties, the improvement of which can also promote plant growth. Compost application confirmed that higher compost DOM results in greater plant biomass. In order to facilitate compost DOM accumulation, we designed a novel composting process which combined aerobic and anaerobic treatments, and the resulting compost (A-Ana compost) with the highest amount of DOM displayed the best performance in promotion of plant growth. A-Ana compost was able to increase maize biomass by 32.71% and 12.40% compared with only anaerobic or aerobic compost, respectively. Therefore, DOM is a critical factor determining compost quality and it is feasible to manipulate composting oxygen supply condition to increase compost DOM, which will lead to increased plant yield.

Incorporation of solar-heated aeration and greenhouse in grass composting

Composting is an environment-friendly method for recycling organic waste, and incorporation of heat and aeration can enhance favorable conditions for microbial growth in the process. This research aimed to evaluate the influence of the introduction of solar heat and aeration to the waste grass exposed to the composting process. The compost piles studied were subjected to different processes: application of solar-heated aeration, only-aeration, solar heating with a greenhouse, and control. Solar-heated air was introduced to a compost pile of grass clippings and compared with a greenhouse compost system. The composting process of 70 days was monitored for temperature, oxygen, moisture, organic matter loss, and humification rate. Germination index has been used to evaluate the maturation of the composts produced. The highest temperature was obtained at the compost pile with the greenhouse. This system reached the highest temperature (68.2 °C) on day 15; the ambient temperature on that day was 20.6 °C. The decreases in the C/N ratios after day 70 of composting were 20% and 15% for the greenhouse and the system where solar-heated air was introduced, respectively. Although the temperature of the solar-heated air was higher than that of the greenhouse, thermophilic temperature levels could not be reached in the aerated compost pile, which indicated a cooling effect of excessive aeration even with the heated air. Composting of grass clippings resulted in a decrease in organic matter content and enhancement in seed germination and root growth, obtaining high GI levels, inferring no phytotoxicity. This study showed that composting of grass clippings with low C/N ratios and high humidity can still be possible by using solar energy.

Impacts of red mud on lignin depolymerization and humic substance formation mediated by laccase-producing bacterial community during composting

The aim of this study was to investigate the impacts of red mud on lignin degradation, humic substance formation and laccase-producing bacterial community in composting to better improve composting performances. The results indicated that the organic matter contents of final compost products in the treatment group with red mud (T) decreased by 25.74%, which was more than the control group without red mud (CK) (12.09%). The final lignin degradation ratio and humic substance concentration of the T were 18.67% and 22.80% higher than that of the CK, respectively. The final C/N values of compost in the CK and T were 11.32 and 10.66, respectively, which were both less than 15, suggesting that compost reached maturity. Redundancy analysis showed that temperature was the main factors driving the variation of laccase-producing bacterial community. Pearson analysis suggested that Pseudomonas, Phenylobacterium, and Caulobacter were the most significantly correlated with lignin degradation and humification in the T.

Insight to nitrification during cattle manure-maize straw and biochar composting in terms of multi-variable interaction

This study investigated nitrification process during cattle manure-maize straw (CM) and biochar (CMB) composting in terms of multi-variable interaction (MVI) among environmental parameters, ammonia-oxidizing archaea (AOA) and bacteria (AOB) community structure, nitrogen-related enzymes as well as substrates using structural equation model (SEM). Results showed that adding biochar significantly reduced potential ammonia oxidation rates. SEM analysis revealed that AOB was affected by temperature and pH, which stimulated the release of urease, increased NH₄⁺-N concentration and finally exerted influence on nitrification in CM. Temperature (0.755) and NO₂^--N (-0.994) were identified as the main factors mediating nitrification in CM and CMB, respectively. Moreover, MVI analysis indicated that nitrification and denitrification occurred simultaneously. Mutual verification of SEM and quantitative analyses (RNA level) confirmed that AOB predominated nitrification. The above results indicated that nitrification could be better explained by MVI using SEM during composting.

Understanding the key regulatory functions of red mud in cellulose breakdown and succession of β-glucosidase microbial community during composting

The purpose of this research was to explore the effects of red mud on cellulose degradation and the succession of β-glucosidase microbial community in composting to better enhance the quality of compost. The activity of β-glucosidase in the treatment group with red mud (T) was 0.42-1.07 times higher than that in the control group without red mud (CK) from day 7 to 21 of composting. The final cellulose degradation ratios of the T (84.73%) were 10.02% higher than that of the CK (74.71%). In addition, Proteobacteria, Actinobacteria, Firmicutes, and Ascomycota were the most dominant β-glucosidase-producing microbes, and these microbes were also the phyla causing composting performances differences in the high temperature, cooling, and maturity periods of CK and T. These results indicated that adding red mud can improve β-glucosidase activity and boost the breakdown of cellulose in composting process.

Effect of enhancers on the phytoremediation of soils polluted by pyrene and Ni using Sudan grass (Sorghum sudanense (Piper) Stapf.)

Remediation of heavy metal and polycyclic aromatic hydrocarbon (PAH)-co-contaminated soils has drawn much more attention; phytoremediation is an often-used technique. Sudan grass (Sorghum sudanense (Piper) Stapf.) with developed root system and strong PAHs and heavy metal tolerance is a potential choice for phytoremediation. In this study, the application of tea saponin (TS) (1 g kg^-1 soil) and nitrilotriacetic acid (NTA) (1 g kg^-1 soil) was to improve the removal efficiency of Ni and pyrene. TS and NTA had no obvious effects on the growth and soluble proteins of Sudan grass. Ni concentration in root was higher than that in the shoot. The addition of TS and NTA increased the Ni concentration in the root by 25.98% in Ni-contaminated treatment. Pyrene was mainly accumulated in the shoot of Sudan grass. Pyrene concentration in shoot increased by 20.14% with TS-NTA in pyrene-contaminated treatment and increased by 31.97% in Ni-contaminated treatment. TS and NTA had significantly improved dissolved organic matter and soil microbial activity. Microbial activity increased by 16.75%, 18.07%, and 23.364% in pyrene-contaminated, Ni-contaminated, and pyrene and Ni-co-contaminated treatment, respectively. This study showed that phytoremediation of pyrene and Ni-co-contaminated soil by Sudan grass could be enhanced by the application of TS-NTA and the interaction between pyrene and Ni impacted the accumulation of Ni and pyrene in Sudan grass.

Industrial composting of low carbon/nitrogen ratio mixtures of agri-food waste and impact on compost quality

The agri-food waste (AW) require amendments for composting to adjust nutritional and physicochemical deficiencies. The theoretical mixtures formulation is difficult to reach on an industrial scale. The main objective of this work was to evaluate to what extent the composition of AW-based mixtures determines the quality of the final compost produced at the industrial scale. Raw materials having the same AW share characteristics, irrespectively of the amendments added, but their compost were different. All the materials were biological stable at the cooling phase, and mature enough at the end, although the degree of humification did not match with the absence of phytotoxicity. The final compost had sufficient quality even though the AW-based raw materials have a low C/N ratio (<20) and other characteristics such as high electrical conductivity (13 mS·cm^-1) and pH (<8.5) that are unfavorable for composting. The management operations during industrial composting correct the deficiencies of raw materials.

Dynamic bacterial assembly driven by Streptomyces griseorubens JSD-1 inoculants correspond to composting performance in swine manure and rice straw co-composting

The effect of Streptomyces griseorubens JSD-1 inoculant on composting performance and bacterial community assembly during the swine manure and rice straw co-composting was studied by a high-throughput pyrosequencing technology. The JSD-1 inoculant contributed to a higher temperature (maximum 66.8 °C), a longer thermophilic phase (46 days), and a lower bacterial diversity in JSD-1 compost. The principle component analysis confirmed that JSD-1 inoculant significantly reshaped the microbial communities. The difference in genera significantly increased during both composting processes. The predominant biomarkers were members of Bacteroidetes in JSD-1 composting. The network analysis also showed different chief "connecting" genera in both composts. Moreover, JSD-1 inoculant increased the total nitrogen, phosphorus, and potassium content in composts. The redundancy analysis showed that the bacterial community was mainly influenced by temperature; additionally, the nutrient contents were positively correlated with temperature. These results demonstrated that JSD-1 inoculant drove the bacterial assembly to induce physicochemical property changes in co-composting.

Molecular mechanisms underlying lignocellulose degradation and antibiotic resistance genes removal revealed via metagenomics analysis during different agricultural wastes composting

In this study, the differences on the physico-chemical parameters, lignocellulose degradation, dynamic succession of microbial community, gene expression of carbohydrate-active enzymes and antibiotics resistance genes were compared during composting systems of bagasse pith/pig manure (BP) and manioc waste/pig manure (MW). The results revealed that biodegradation rates of organic matter, cellulose, hemicellulose and lignin (29.14%, 17.53%,45.36% and 36.48%) in BP were higher than those (15.59%, 16.74%, 41.23% and 29.77%) in MW. In addition, the relative abundance of Bacillus, Luteimonas, Clostridium, Pseudomonas, Streptomyces and expression of genes encoding carbohydrate- active enzymes in BP were higher than those in MW based on metagenomics sequencing. During composting, antibiotics and antibiotic resistance genes were substantially reduced, but the removal efficiency was divergent in the both samples. Taken together, metagenomics analysis was a potential method for evaluating lignocellulose's biodegradation process and determining the elimination of antibiotic and antibiotic resistance genes from different composting sources of biomass.

Insights into the functionality of fungal community during the large scale aerobic co-composting process of swine manure and rice straw

Composting is a cost-efficient method of transferring various unstable and complex organic matters into a stable and humus-like substance, during which various fungus play a critical role in the decomposition of organic matters. In this study, the rice straw and swine manure co-composting were carried out in a pilot-scale, and the evolution of various biochemical parameters and fungi community were detected at different time points. The results showed that most of the parameters fluctuated strongly at the thermophilic phase (THP), and the Canonical Correlation Analysis (CCA) results showed that Mycothermus spp. and Aspergillus spp. were with abundances of 47.82% and 3.51%, respectively, which were considered as the core fungi during the composting process. In addition, five culturable thermophilic filamentous fungi were isolated from the samples obtained at the high temperature stage, among which Aspergillus fumigatus were considered as the core specie at this special phase. The capacity of lignocellulose degradation of this strains was also evaluated by analyzing the secretomes in a coculture group with rice straw and crystalline cellulose as carbon sources, and the identified proteins illustrated that the enzymes were chiefly secreted by A. fumigatus in both treatments, with the abundances of 91.41% and 85.19%, respectively.

Integral approach using bacterial microbiome to stabilize municipal solid waste

Biological transformation of municipal solid waste is an environment-friendly management strategy against recalcitrant residues. The bacterial biome that inhabit said residues are responsible of decomposing both simple and complex materials. For this reason, processes such as composting, which favor the acceleration of the transformation of organic matter, can contribute to the degradation of municipal solid waste. Not only as mere fertilizer for crops, but also as methods for the recovery of solid waste. However, the control of the conditions necessary to achieve an optimal process on an industrial scale is a great concern. Thus, the aim of this work focuses on the characterization of the bacterial microbiome on three municipal solid waste facilities in order to deepen the role of microorganisms in the state of the final product obtained. For it, an intensive metagenomic analysis as well as a battery of physicochemical determinations were carried out. The lack of adequate thermophilic phases was decisive in finding certain bacterial genera, such as Lactobacillus, which was significant through these processes. Biodiversity did not follow a common pattern in the three processes, neither in abundance nor in richness but, in general, it was greater during the bio-oxidative stage. Despite the different trend in terms of the degradation of carbon fractions in these wastes, at the end of the biodegradation treatments, a sufficient degree of bioestabilization of the organic matter was reached. The results offer the opportunity to obtain a level of detail unprecedented of the structure, dynamics and function of the bacterial community in real conditions, without the control offered by laboratory conditions or pilot plants.

Investigating the variation of dissolved organic matters and the evolution of autotrophic microbial community in composting with organic and inorganic carbon sources

The main purpose of this study was to analyze the effects of different carbon source (Na₂CO₃, NC; sugarcane molasses, SM) additives on dissolved organic matter (DOM), cbbL-containing autotrophic microbes (CCAM), and the relationship among physico-chemical parameters, DOM and CCAM to better understand carbon transformation in composting. The results showed that SM or NC additive could promote the degradation and transformation of OM and DOM. After adding SM or NC, the Simpson index decreased by 2.03% and 0.51%, respectively, and Luteimonas and Thermomonspora were detected using high throughput sequencing, indicating that SM and NC increased the diversity of CCAM community. Additionally, both NC and SM contributed to improve the abundance of cbbL gene (45.91% and 2.15%) based on fluorescence quantitative PCR (qPCR) analysis at the cooling phase of composting. Pearson correlation analysis revealed that Proteoobacteria, Firmicutes, Acidobacteria and Nematoda were positively related with C/N, OM and DOM (0.5 < R < 0.9, P < 0.05).

Evaluating the influence of raw materials on the behavior of nitrogen fractions in composting processes on an industrial scale

Success of composting as an ecological technology for organic waste management has allowed its implementation in the current circular economy models. However, composting on an industrial scale often shows drawbacks and peculiarities. In this work, a comparative analysis of 15 industrial composting facilities was carried out in which different anthropogenic organic waste were processed. Results showed that composting process on an industrial scale did not always evolve in a standard way. Monitoring parameters as well as enzymatic activity depended largely on the raw materials and were strongly linked to the transformation of nitrogen fractions. Despite the heterogeneity of the processes and raw materials, microbial activity managed to the optimal biotransformation, obtaining products that comply with the agronomic quality standards. This work represents a breakthrough in composting and provides new knowledge for better management of this process on an industrial scale.

Enhancement of converting corn stalk into reducing sugar by ultrasonic-assisted ammonium bicarbonate pretreatment

In order to improve the yield of reducing sugar from corn stalk, ultrasonic-assisted ammonium bicarbonate pretreatment of corn stalk was proposed. Three ultrasonic factors (time (0-30 min), temperature (30-60 °C) and liquid/solid mass ratio (5-20)) were optimized by response surface experiment. The optimal conditions of ultrasonic pretreatment were obtained (liquid/solid mass ratio is 12:1, temperature is 42 °C and time is 11 min). The highest saccharification rate of corn stalk was of 82.61%, which was remarkably increased by 355% compared to the control group.

Biochemical Characterization of Xylanases from Streptomyces sp. B6 and Their Application in the Xylooligosaccharide Production from Viscose Fiber Production Waste

Enzymatic hydrolysis of xylan represents a promising way to produce xylooligosaccharide (XOS), which is a novel ingredient in functional food. However, the recalcitrance of xylan in natural lignocellulosic biomass entails effective and robust xylanases. In the present study, we reported the isolation of a thermophilic Streptomyces sp. B6 from mushroom compost producing high xylanase activity. Two xylanases of Streptomyces sp. B6 belonging to GH10 (XynST10) and GH11 (XynST11) families were thus identified and biochemically characterized to be robust enzymes with high alkaline- and thermostability. Direct hydrolysis of neutralized viscose fiber production waste using XynST10 and XynST11 showed that while XynST10 produced 23.22 g/L XOS with a degree of polymerization (DP) of 2-4 and 9.27 g/L xylose, XynST11 produced much less xylose (1.19 g/L) and a higher amounts of XOS with a DP = 2-4 (28.29 g/L). Thus, XynST11 holds great potential for the production of XOS from agricultural and industrial waste.

Monitoring of Fruit and Vegetable Waste Composting Process: Relationship between Microorganisms and Physico-Chemical Parameters

The aim of this study was to investigate and evaluate the composting potential of fruit and vegetable waste with sawdust in different combinations and to establish the relationship between microorganisms and physico-chemical parameters. Three samples were made with the C/N ratios of 50 (sample 1), 45 (sample 2), and 30 (sample 3) by adding fruit waste (apple, banana, orange, and kiwi peels) and vegetable waste (cabbage leaves, potato and carrot peels). The total amount of fruit and vegetable waste was approximately 2 kg in each sample to which different quantities of sawdust were added (1.23, 0.14, and 0.203 kg) in order to obtain the C/N ratios proposed and to limit the odor. Composting process was monitored over 70 days, while physico-chemical and microbiological analyses were performed. Results showed that in the first week pH is acidic and electrical conductivity values are high for all three samples, and then the pH values increase during the composting process, while electrical conductivity values decrease. The nitrogen content is low in all samples and will decrease during the first five weeks of the composting process, then begin to increase slightly. Cr, Cu, Ni, and Zn values in the all three compost samples are below threshold values. During the composing process the microbial communities are constantly changing. The compost was successfully obtained and meets the requirement standards for agricultural use. It can be concluded that there is statistically significant association between the microorganisms and physico-chemical indicators.

Effect of microbial inoculation on physicochemical properties and bacterial community structure of citrus peel composting

In this study, microorganisms were inoculated during citrus peel composting for citrus waste recycling and valorisation. The physicochemical properties and the bacterial community structure of citrus peel composting inoculated microorganism were studied. The thermophilic stage of pilot-scale composting (T2) was 20 days longer than lab-scale composting (T1). C/N, organic matter, moisture, pectin and cellulose content decreased along with composing process, but the pH, soluble protein and total nutrient showed an opposite trend. The inoculation improved the richness and diversity of the bacterial community and the diversity index reached maximum on 21 days. As composting progress, Bacillus, Sphingobacterium and Saccharomonospora in inoculum became the dominant genus. Redundancy analysis showed that C/N, pectin degradation rate and temperature could explain 30.1%, 24.9% and 15.6% of the variation in bacterial genera, respectively.

Exploring the characteristics of dissolved organic matter and succession of bacterial community during composting

The objective of this study was to explore the relationships among physico-chemical parameters, dissolved organic matters (DOM), and bacterial community during composting to better understand composting performances. The results showed total Kjeldahl nitrogen (TKN) (57%), temperature (39%), and pH (3%) were main factors driving the succession of bacterial communities. Firmicutes was a crucial phylum degrading organic matters for DOM formation, whereas the aromaticity and humification of DOM were closely related to Luteimonas (R² = 0.971, p < 0.05) and Sphingobacteriaceae (R² = 0.931, p < 0.05). Additionally, total phosphorus (TP), total potassium (TK), and TKN increased by 34.84%, 43.66%, and 65.91%, respectively, while organic matter decreased by 61.79%. The final compost had a C/N of 6.91 (<15) and a germination index of 97.81% (>80%), indicating that compost reached maturity and could be safely applied for soil amendment.

Effects of inoculation with lignocellulose-degrading microorganisms on antibiotic resistance genes and the bacterial community during co-composting of swine manure with spent mushroom substrate

Composting is usually employed to treat livestock manure, and inoculation with lignocellulose-degrading microorganisms can enhance the quality of compost. In this study, lignocellulose-degrading microorganisms were inoculated at two levels (uninoculated control = 0%, and T treatment = 10%) during co-composting of swine manure with spent mushroom substrate, and their effects on antibiotic resistance genes (ARGs) and the bacterial community were investigated. Inoculation with lignocellulose-degrading microorganisms caused greater decreases in 6/11 ARGs and 3/4 mobile genetic elements than the control. The total relative abundances of ARGs increased by 0.23 logs in the control but decreased by 0.08 logs in the T treatment after co-composting. The bacterial community was clustered according to the composting time in the two treatments, where inoculation mainly affected the bacterial community during the mesophilic phase. Redundancy analysis and network analysis showed that the bacterial community succession had important effects on the variations in ARGs. Inoculation with lignocellulose-degrading microorganisms led to the reduction of ARGs, which was significantly correlated with the abundances of potential host bacteria for ARGs. Thus, inoculation with lignocellulose-degrading microorganisms could decrease the risk of ARGs spreading and make compost products more security.