Dominant Functional Microbial Communities In Natural Lignocellulosic Composts Revealed By Integrated

In China, tons of wastes derived from agriculture and animal husbandry are produced every year. The most common way to deal with these organic wastes is stacking or burning, leading to the serious pollution of soil, water as well as air. Besides, due to the large-scale land intensification and crop growth in successive years, meanwhile lacking of the crop rotation system, the soil fertility was greatly overdraught and the water and soil loss was more and more severe. To solve the current environmental issue caused by agriculture and animal husbandry, the efficient and environmental benign method is urgently needed. Composting technology which can perform the biotransformation of organic wastes and turn them into excellent organic fertilizer, is therefore a promising method for the innocent treatment and recycling of agriculture and animal husbandry wastes.Composting process is mainly driven by microbial communities. During the process of transformation of different organic materials including crop straw and livestock manure, diverse microbes cooperatively degrade the substrates. However, the studies of compost communities are still less systematic and comprehensive so far. To solve this problem, in this paper series of studies of microbial communities in natural lignocellulosic composts were performed, and the main results were listed as follow:1. Successfully using meta-omics to identify the dominant functional microbial communities in natural maize straw compostsUsing the integrated meta-omics including metagenomics and metaproteomics, the dynamic changes of composition and structure of microbial communities in natural maize straw composts with spatio-temporal variation were tracked, and the function of dominant communities was identified. The results indicated that during the composting process, a stable and simple structure of compost communities developed, composed of Thermomyces, Thermobifida and Thermopolyspora, which were also the functional microbes in lignocellulose degradation. Thermomyces lanuginosuswas the most dominant fungus in hemicellulose degradation, and Thermobifida fuscawas the most dominant cellulose degrader. The meta-omics can link the composition and function of microbial communities, therefore the dominant functional microbes can be located in composts. Besides, the meta-omics can also be used for the study of microbial communities in other habitats, and has wide universality.2. A 90 m3 large-scale fermentor was successfully used for the industrialized application of compostsWith a 90 m3 large-scale fermentor, the corncob and cow dung composts with a height of 3.3 m was performed, and meta-omics was applied for the study of microbial communities. The results showed that by fermentor compost, the fermentation cycle could be shortened from 42 days to 11 days, greatly improving the composting efficiency. In addition, the meta-omic results indicated that obvious species succession of compost communities occurred with time and depth. In fermentor compost, the most dominant microbes included the bacteria Thermobifida and Bacillus, as well as the fungi Thermomyces and Aspergillus. The genus Thermobifida was the dominant cellulose degrader in fermentor compost.This study successfully reformed the tranditional composting technology, and realized the modernization of composting process. Besides, the meta-omic results could provide guiding significance to the production of microbial agents.3. The meta-omic study of wheat straw compost communties revealed that due to the high heterogeneity of structure, as well as high content of lignocellulose and silicon, wheat straw composts were less efficient when compared with maize straw compostsBased on the results of maize straw composts, the dynamic changes of microbial communities in wheat straw compost were tracked by integrated meta-omics. Compared with maize straw composts, the species succession of micrbial communities did not occur in wheat straw composts. The lignocellulose was just partly degraded, and the compost temperature was lower than 60℃, thus the composts were failed to perform the innocent treatment of substrates. Thus the pathogenic Bacteroidetes and Proteobacteria were the dominant microbes among the composting process. These results revealed that compared with maize straw composts, wheat straw composts had less efficient degradation rate, which might be due to the wax arounding the surface of wheat straw.4. The meta-omic studies of microbial communities in chicken manure composts revealed that Bacillus was the dominant functional microbeChicken manure contains high ratio of nitrogen and low water content, which makes it an excellent substrate for composting. Using the chicken manure from poultry farms as a substrate for composting, the microbial communities in which were studied by meta-omics. The results indicated that obvious species succession occurred over time and depth. Firmicutes was the most dominant microbe in compost, represented of Bacillus. The results of zymogram also showed that the most dominant protein bands were belonged to this genus. Therefore, the Bacillus was the most dominant functional microbe in this kind of chicken manure composts. These results also indicated that different composting substrates had significant influence on microbial communities. This study has great theoretical value in researching the rapid management of livestock manure.5. The analysis of expression profile of the dominant degrading fungus T. lanuginosusshowed that natural substrates were the excellent inducer of xylanases secreted by this speciesT. lanuginosusis the dominant hemicellulose degrader in natural maize straw composts. In this study the expression profile of T. lanuginosuswas researched. The results showed that when cultivated by liquid fermentation, T. lanuginosuscould use xylose as a substrate to reach the maximum mass growth. Compared with liquid fermentation by simple substrates, when fermented by natural complicated substrates, better growth situation was observed. In addition, both of maize straw and wheat bran could induce the high expression of xylanase. These results lay the foundation for further study of the ecological function mechanism and function of T. lanuginosus in composts.