Upgrade from aerated static pile to agitated bed systems promotes lignocellulose degradation in large-scale composting through enhanced microbial functional diversity

Composting presents a viable management solution for lignocellulose-rich municipal solid waste.However,our understanding about the microbial metabolic mechanisms involved in the biodegradation of lignocellulose,particularly in industrial-scale composting plants,remains limited.This study employed metaproteomics to compare the impact of upgrading from aerated static pile(ASP)to agitated bed(AB)systems on physicochemical parameters,lignocellulose biodegradation,and microbial metabolic pathways during largescale biowaste composting process,marking the first investigation of its kind.The degradation rates of lignocellulose including cellulose,hemicellulose,and lignin were significantly higher in AB(8.21%-32.54%,10.21%-39.41%,and 6.21%-26.78%)than those(5.72%-23.15%,7.01%-33.26%,and 4.79%-19.76%)in ASP at three thermal stages,respectively.The AB system in comparison to ASP increased the carbohydrate-active enzymes(CAZymes)abundance and production of the three essential enzymes required for lignocellulose decomposition involving a mixture of bacteria and fungi(i.e.,Actinobacteria,Bacilli,Sordariomycetes and Eurotiomycetes).Conversely,ASP primarily produced exoglucanase andβ-glucosidase via fungi(i.e.,Ascomycota).Moreover,AB effectively mitigated microbial stress caused by acetic acid accumulation by regulating the key enzymes involved in acetate conversion,including acetyl-coenzyme A synthetase and acetate kinase.Overall,the AB upgraded from ASP facilitated the lignocellulose degradation and fostered more diverse functional microbial communities in large-scale composting.Our findings offer a valuable scientific basis to guide the engineering feasibility and environmental sustainability for large-scale industrial composting plants for treating lignocellulose-rich waste.These findings have important implications for establishing green sustainable development models(e.g.,a circular economy based onmaterial recovery)and for achieving sustainable development goals.

The Character of Normal Temperature Straw-Rotting Microbial Community

In order to study degradation capability and optimal condition of produced endoglucanase （CMCcase）, the microbial community with efficient cellulose degrading ability in 28℃ was studied. Microbial community came from rotted rice straw which was enriched and domesticated by improved Mandels medium. The standard cellulase activity assays were used to determine cellulase activity, degradation products were analyzed by gas chromatography mass spectrometry （GC/MS）, and denaturing gradient gel electrophoresis （DGGE） was used to identify the composition dynamic of the community. The results showed that the microbial community could degrade 39.6% of rice straw gross weight within 6 d. When culture medium volume was 1/5 and pH = 6 on day 5, the CMCcase activity reached the highest of 14 IU mL-L During the fermentation, more than ten products were detected using GCMS. The microbial changed lots in different fermentation periods which detected by DGGE. Phylogenetic tree derived from 16S rDNA sequence found that the community composed of bacteria, and the closest relative were belong to Clostridium sp., Brevibacillus sp. and Bacterium sp. This microbial community could accelerate rice straw rotting and decomposed products could promote organic matter increase of soil

Selective ligninolysis of wheat straw and wood chips by the white-rot fungus Lentinula edodes and its influence on in vitro rumen degradability

Background： The present work investigated the influence of lignin content and composition in the fungal treatment of lignocellulosic biomass in order to improve rumen degradability. Wheat straw and wood chips,differing in lignin composition, were treated with Lentinula edodes for 0, 2, 4, 8 and 12 wk and the changes occurring during fungal degradation were analyzed using pyrolysis-gas chromatography-mass spectrometry and detergent fiber analysis.Results： L. edodes preferentially degraded lignin, with only limited cellulose degradation, in wheat straw and wood chips, leaving a substrate enriched in cellulose. Syringyl（S）-lignin units were preferentially degraded than guaiacyl（G）-lignin units, resulting in a decreased S/G ratio. A decreasing S/G ratio（wheat straw： r =-0.72, wood chips： r =-0.75） and selective lignin degradation（wheat straw： r =-0.69, wood chips： r =-0.88） were correlated with in vitro gas production（IVGP）, a good indicator for rumen degradability.Conclusions： L. edodes treatment increased the IVGP of wheat straw and wood chips. Effects on IVGP were similar for wheat straw and wood chips indicating that lignin content and 3D-structure of cell walls influence in vitro rumen degradability more than lignin composition.

The effect of particle size and amount of inoculum on fungal treatment of wheat straw and wood chips

Background： The aim of this study was to optimize the fungal treatment of lignocellulosic biomass by stimulating the colonization. Wheat straw and wood chips were treated with Ceriporiopsis subvermispora and Lentinula edodes with various amounts of colonized millet grains（0.5, 1.5 or 3.0 % per g of wet weight of substrate） added to the substrates. Also, wheat straw and wood chips were chopped to either 0.5 or 2 cm.Effectiveness of the fungal treatment after 0, 2, 4, 6, or 8 wk of incubation was determined by changes in chemical composition, in vitro gas production（IVGP） as a measure for rumen degradability, and ergosterol content as a measure of fungal biomass.Results： Incomplete colonization was observed for C. subvermispora treated wheat straw and L. edodes treated wood chips. The different particle sizes and amounts of inoculum tested, had no significant effects on the chemical composition and the IVGP of C. subvermispora treated wood chips. Particle size did influence L.edodes treatment of wheat straw. The L. edodes treatment of 2 cm wheat straw resulted in a more selective delignification and a higher IVGP than the smaller particles. Addition of 1.5 % or 3 % L. edodes inoculum to wheat straw resulted in more selective delignification and a higher IVGP than addition of 0.5 % inoculum.Conclusion： Particle size and amount of inoculum did not have an effect on C. subvermispora treatment of wood chips. At least 1.5 % L. edodes colonized millet grains should be added to 2 cm wheat straw to result in an increased IVGP and acid detergent lignin（ADL） degradation.

Multipartite symbioses in fungus-growing termites (Blattodea: Termitidae, Macrotermitinae) for the degradation of lignocellulose

Fungus-growing termites are among the most successful herbivorous animals and improve crop productivity and soil fertility.A range of symbiotic organisms can be found inside their nests.However,interactions of termites with these symbionts are poorly understood.This review provides detailed information on the role of multipartite symbioses(between termitophiles,termites,fungi,and bacteria)in fungus-growing termites for lignocellulose degradation.The specific functions of each component in the symbiotic system are also discussed.Based on previous studies,we argue that the enzymatic contribution from the host,fungus,and bacteria greatly facilitates the decomposition of complex polysaccharide plant materials.The host-termitophile interaction protects the termite nest from natural enemies and maintains the stability of the microenvironment inside the colony.