Deciphering the effect of exogenous lignocellulases addition on the composting efficiency and microbial communities.

This study aimed to reveal the potential effects of exogenous lignocellulases addition on the composting efficiency and microbial communities. The lignocellulases addition at the mesophilic phase (MEP) greatly expedited the substrate conversion and the rise of temperature at the initial stage, driving the early arrival of thermophilic phase (THP), caused by the positive effects of Sphingobacterium and Brevundimonas. When being added at the THP, the potential functions and interactions of microbial communities were stimulated, especially for Thermobispora and Mycothermus, which prolonged the duration of the THP and expedited the humic acid formation. Simultaneous addition (MEP and THP) significantly altered the microbial community succession and activated the microbes that contributed to the lignocellulases secretion, exhibiting the highest cellobiohydrolase (36.19 ± 3.25 U· g-1 dw) and xylanase (47.51 ± 3.32 U·g-1 dw) activity at the THP. These findings provide new strategies that can be effectively utilized to improve the efficiency and quality of composting.

The functions of potential intermediates and fungal communities involved in the humus formation of different materials at the thermophilic phase.

Humus is the final product of humus precursors (HPS) during the humification process, while the associated mechanisms of humus formation have not been clarified. Here, the HPS degradation intermediate and core fungal function for wheat straw and chicken manure compost (SCM), cow dung compost (CD), Chinese traditional medicine residue compost (CTM) and mushroom dreg and chicken manure compost (MCM) was investigated during the thermophilic phase. The results showed SCM and MCM were rich in proteins, lipids, cellulose, low-molecular-weight organic acids, while CD and CTM contained abundant carbohydrates, aliphatic compounds, easily biodegradable aromatic structures, and intermediates from the lignocellulose degradation. In particular, the HPS degrading intermediates including O-alkyl-C and aromatic C compounds were the critical factors, and Scedosporium, Hypsizygus and Remersonia were the core fungal genera for the humification. Furthermore, the potential fungal functional genes involved in carbohydrate and lignin degradation might be the key factors to drive the humification process.

Functional characterization of a novel copper-dependent lytic polysaccharide monooxygenase TgAA11 from Trichoderma guizhouense NJAU 4742 in the oxidative degradation of chitin.

Lytic polysaccharide monooxygenases (LPMOs) are attracting much attention for their potential application in biodegradation. However, there are limited studies on the characterization of the AA11 family. Here, a novel AA11 family protein, TgAA11, from Trichoderma guizhouense NJAU 4742 was characterized, and the isothermal titration calorimetry (ITC) analysis results showed that it exhibited tight binding capacity for copper ions with a Kd value of 4.83 ± 0.79 µM. The MALDI-TOF-MS analysis results indicated that TgAA11 could act on ß-chitin to form C1 oxidation products, and some deacetylated chitooligosaccharides. In addition, the degradation of α-chitin and ß-chitin by a chitinolytic enzyme Sg-chi was substantially increased in the presence of TgAA11 by 39.9 % and 288.2 %, respectively. Furthermore, the active site residues predicted showed that His61 and Tyr142 might be critical for the active site residues of the TgAA11 protein. This study will contribute to the understanding of the function of AA11 LPMOs in the degradation of chitin.

Contributions of the biochemical factors and bacterial community to the humification process of in situ large-scale aerobic composting.

Multiple types of biochemical parameters were determined in the course of the composting process with rice straw and Chinese traditional medicine residues as substrates. The water-soluble fractions (WSFs) were analyzed by excitation-emission-matrix fluorescence (EEM-FL), and the maximum PV/III value (1.2) was observed in thermophilic phase (THP). Bacterial community analysis results indicated that the genera with the capacity of degrading lignocellulose dominated in mesophilic phase (MEP) and THP. The metabolic pathways based on KEGG analysis revealed that the amino acid, carbohydrate and energy metabolism pathways in THP were higher than the other two phases. The correlation analysis between EEM-FL and the bacterial community revealed that the genera with high abundances in the THP were significantly positively correlated with fulvic acid-like materials and humic acid-like organics. The quantification results of the lignocellulose-degrading genes in different phases further verified the key functional bacteria obtained by correlation analysis during the composting process.

Bacterial ecosystem functioning in organic matter biodegradation of different composting at the thermophilic phase.

This study aimed to provide insights into prediction of composting ecological functioning through analyzing the critical bacterial populations and functions. The bacterial ecosystem functioning was essential, and cow dung, chicken manure, mushroom dreg and Chinese medicine residues were used as raw materials to quantify and predict the functioning of bacterial communities through synthetic spike-in standards accompanied Illumina sequencing and PICRUSt. Bacterial community of wheat straw and chicken manure compost (SCM) was similar to mushroom dreg and chicken manure compost (MCM), and Sinibacillus dominated in both treatments with the abundance of 20.73% and 41.36%, respectively. The correlation analysis between bacterial community and fluorescence EEM regional integration parameters showed that Lactobacillus (0.889), Enterococcus (0.888) and Erysipelothri (0.903) were positively correlated with PV, n / PIII, n. The ontology analysis results showed that metabolism, genetic information processing, environmental information processing and cellular processes were the primary functions for bacterial community in all treatments.

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.

Pan-Genome Analyses of Geobacillus spp. Reveal Genetic Characteristics and Composting Potential.

The genus Geobacillus is abundant in ecological diversity and is also well-known as an authoritative source for producing various thermostable enzymes. Although it is clear now that Geobacillus evolved from Bacillus, relatively little knowledge has been obtained regarding its evolutionary mechanism, which might also contribute to its ecological diversity and biotechnology potential. Here, a statistical comparison of thirty-two Geobacillus genomes was performed with a specific focus on pan- and core genomes. The pan-genome of this set of Geobacillus strains contained 14,913 genes, and the core genome contained 940 genes. The Clusters of Orthologous Groups (COG) and Carbohydrate-Active Enzymes (CAZymes) analysis revealed that the Geobacillus strains had huge potential industrial application in composting for agricultural waste management. Detailed comparative analyses showed that basic functional classes and housekeeping genes were conserved in the core genome, while genes associated with environmental interaction or energy metabolism were more enriched in the pan-genome. Therefore, the evolution of Geobacillus seems to be guided by environmental parameters. In addition, horizontal gene transfer (HGT) events among different Geobacillus species were detected. Altogether, pan-genome analysis was a useful method for detecting the evolutionary mechanism, and Geobacillus' evolution was directed by the environment and HGT events.

Evolution of various fractions during the windrow composting of chicken manure with rice chaff.

Different fractions during the 85-day windrow composting were characterized based on various parameters, such as physiochemical properties and hydrolytic enzyme activities; several technologies were used, including spectral scanning techniques, confocal laser scanning microscopy (CLSM) and 13C Nuclear Magnetic Resonance Spectroscopy (13C NMR). The evaluated parameters fluctuated strongly during the first 3 weeks which was the most active period of the composting process. The principal components analysis (PCA) results showed that four classes of the samples were clearly distinguishable, in which the physiochemical parameters were similar, and that the dynamics of the composting process was significantly influenced by C/N and moisture content. The 13C NMR results indicated that O-alkyl-C was the predominant group both in the solid and water-soluble fractions (WSF), and the decomposition of O-alkyl-C mainly occurred during the active stage. In general, the various parameters indicated that windrow composting is a feasible treatment that can be used for the resource reuse of agricultural wastes.