Construction Of Cellulose Hemicellulose In The Compost Of Silkworm Mulberry Branches And Its Mechanism Of Action

The silkworm industry in Guangxi is booming.The output of silkworm excrement and mulberry branches is large and the utilization rate is low.High temperature composting can accelerate the decomposition of silkworm excrement and mulberry branches,improve soil fertility,improve soil microbial structure,and curb the spread of pathogenic bacteria in mulberry gardens to a certain extent.Silkworm excrement and mulberry branches are high-quality composting materials,rich in nitrogen,phosphorus,potassium,organic matter,amino acids and other nutrient elements and substances that can improve crop yield and quality.Lignocellulose in the composting process is the main substance available to microorganisms and is difficult to degrade,and the degradation of lignocellulose can characterize the maturity of compost.The addition of exogenous bacteria can change the number and types of microorganisms in compost,accelerate the degradation of lignocellulose and promote the maturity of compost.(1)Five highly active cellulose degrading bacteria and five hemicellulose degrading bacteria were isolated from silkworm excrement mulberry branch compost.After identification,10 strains belong to Bacillus,Bjerkandera,Trichoderma,Cladosporium and Trametes;The cellulose degrading bacteria were named as: Bacillus cereus ZXX 、 Bjerkandera adusta strain ZX6 、 Trichoderma harziamm ZXL 、Cladosporium sp.strian ZXY and Cladosporium sp.strian ZBX;hemicellulose degrading bacteria were named as Cladosporium cladosporides strian BZA1 、Cladosporium sp.BZQ、Cladosporium sp.BZ10、Trametes sp.BZ22 and Bacillus licheniformis strain BX6。(2)Field composting verification showed that the addition of the above exogenous bacteria significantly improved the maturity,cellulase activity and hemicellulase activity of silkworm excrement mulberry branch compost,promoted the degradation of cellulose and hemicellulose in compost,accelerated the decomposition of lignocellulose and promoted the maturity of compost.At the end of the composting,the degradation rates of SMC and SMHC cellulose increased by 6.44% and 5.78%,and the degradation rates of hemicellulose increased by 16.75% and 14.31%,respectively,compared with the control group.(3)The addition of the exogenous flora significantly increased the relative abundance of microorganisms in silkworm excrement mulberry branch compost,such as Thermomyces,Bacillus and Thermobifida,which can promote the degradation of lignocellulose in the high temperature stage and maturity stage,and reduced the relative abundance of pathogenic bacteria such as Staphylococcus and Enterococcus in the maturity stage.Random forest analysis showed that Bacillus,Ascomycota and Aspergillus all played a major role in lignocellulose degradation,and the abundance of these three kinds of bacteria was always significantly positively correlated with the activity of endoglucanase.Cellulose degrading bacteria and hemicellulose degrading bacteria promote the degradation of lignin in composting by activating the strains with lignocellulose degradation function such as Bacillus,Ascomycota and Aspergillus in composting,so as to promote them to produce more degrading enzymes,so as to improve the efficiency and quality of composting.In conclusion,the addition of cellulose degrading bacteria and hemicellulose degrading bacteria activated most of the microorganisms with lignocellulose degradation function in the silkworm excrement mulberry branch composting system,changed the community structure and function,accelerated the degradation of lignocellulose,It promotes the decomposition of silkworm sand mulberry branch compost,which is of great significance for the green and sustainable development of Guangxi’s silkworm industry.