The Dynamics Of Microbial Communities In Different Composts And Analysis Of Extracellular Enzymes Of Predominant Filamentous Fungi

Compost is a lignocellulose degrading system driven by the activities of microbes. In this study, the dynamic changes of microbiota from three composts with different substrates, including chicken manure, mushroom residue and corn straw with compost materials, temporal and spatial variation were researched by high-throughput sequencing approach. Meanwhile, a strain was isolated from maize straw compost and identified as Thermomyces lanuginosus, the function of exoenzymes of which was studied under different substrate condition as well. In addition, the endo-xylanase XYNA secreted by this species was cloned and expressed in Pichia pastoris GS115 to determine its enzymatic properties. This work can provide direction to microbial agent compound and the optimization of high-producing strain, and the materials to the improvement of the thermostability of xylanase.In this paper, the following work was performed:1. Dynamics of microbial communities in three kinds of compostThe microbial communities in mushroom residue composting, chicken manure composting and straw biomass composting were different. However, frrnicutes, actinomyces, acteroidetes and poteobacteria was the main four big community in quantity. In mushroom residue composting, acteroidetes and poteobacteria was preponderant in its microbial community. We improved the content of nitrogen source in chicken manure composting. And results suggested, acteroidetes and poteobacteria obviously decresed, and firmicutes occupied highest percentage followed by actinomyces. In corn straw biomass composting, the preponderant communiy was actinomyces fungi mainly from ascomycetes in corn straw compost, especially Thermomyces lanuginosus is main filamentous fungi.2. A strain of Thermomyces lanuginosus was isolated from the corn straw compost.Thermomyces lanuginosus can secrete many thermophilic degrading enzymes and is important to degrade lignocellulose. A strain of Thermomyces lanuginosus was isolated from corn straw compost, named sduw-01.3. The composition and function of exoenzymes secreted by T. lanuginosus under different substrates conditionThe strain T. lanuginosus was cultured in liquid culture used xylose, xylitol and arabinose as sole carbon source respectively, and we found that xylose could induce more xylanases than other two monosaccharides, while xylitol induced least xylanase expression. When it was cultured in more complex substrates for solid fermentation, including com straw, wheat bran and the mixture of them, the highest content of xylanases was obtained under the mixture condition. Besides, proteases were detected in crude enzymes of all these six substrates, and more content were obtained under solid fermentation condition.4. Xylanase XYNA was expressed in Pichia Pastoris strain GS115.The RNA was extracted and reversed into cDNA. Then xynA was amplified used the cDNA as template and was expressed in pichia GS115 successfully. After concentration and purification of xylanase XYNA, enzymology properties showed that the its optimum temperature was 70 ℃, its optimum pH was 6.2. Enzyme activity could keep 100% of after being treaded for 2 hours under 60 ℃. The main products of the degradation of xylan was mainly xylobiose and xylotriose, containing a few xylose and xylotetraose.