Effect of different indigenous microorganisms and its composite microbes on degradation of corn straw

Abstract: In nature, there are a large number of microorganisms that can decompose the cellulose of the wood, including bacteria, fungi and actinomycetes. It has been found that the bacteria bacillus and pseudomonas, streptomyces, fungi and other microorganisms are playing an important role in the aerobic fermentation process at different stages. In this study, 8 kinds of microorganisms were selected to construct efficient composite microbes for corn straw degradation. They were identified to be Gloeophyllum trabeum, Bacillus circulans, Pseudomonas aeruginosa, Streptomyces badius, Phanerochaete chrysosporium, Coriolus versicolor, Trichoderma viride and Aspergillus niger. Lignocellulose degradation rate of single strain and the antagonism between different strains were firstly analyzed. The 90 mL liquid for the expanding culture was added to the triangular flask containing 30 g corn straws, which was then put in the incubator with constant temperature of 30℃ and humidity controlled at more than 80% for 35 d. Corn straws treated by pretreatment of microorganisms were sampled for determination of cellulose, hemicellulose and lignin every 5 days. The results showed that the degradation rates of hemicellulose reached up to 47.81% and 37.53% after the fermentation processes with Aspergillus niger and Trichoderma viride respectively, and those of cellulose reached 38.96% and 46.32% respectively. The lignin degradation rates reached up to 43.56% and 39.17% respectively after pretreatments with Phanerochaete chrysosporium and Coriolus versicolor. The bacteria and actinomycetes in this study did not have a great ability to degrade corn straws. The results showed that corn straws were not completely degraded in the process of pretreatment by microorganisms. Because of the complex structure of lignocellulose, the degradation of corn straws required the participation of many kinds of microorganisms. However, the construction of composite microbes was not a simple superposition of microorganisms. The antagonism was determined for microorganisms by ?at-stand and Oxford plate methods. No antagonistic reaction was observed between the fungi, actinomycetes and bacteria used in this study, which provided the basis for the construction of the composite microbes. Then, a group of composite microbes were preliminarily constructed to degrade the corn straws for 15 d. The results from the scanning electron microscopy (SEM) turned out that the structure of pretreated straw changed a lot and some cracks and cavities which increased the availability of lignocellulose were found. The degradation rate of lignin, cellulose and hemicellulose in the corn straw gradually increased in the process of the pretreatment with composite microbes. After the pretreatment process, the degradation rates of hemicellulose, cellulose and lignin reached up to 48.53%, 36.38% and 40.11% respectively. While increasing the lignin degradation rate, the consumption of cellulose was reduced, which was more conducive to the subsequent anaerobic fermentation. The research provides the reference for the degradation and utilization of straw biomass.