Screening of a cellulose-degrading bacterium and its degradation effect on sugarcane leaf

【Objective】 To screen bacteria with degradation effects on sugarcane leaves，and to provide reference for application of bacteria in sugarcane leaf returning and development of efficient biological decomposition agents and cellulase preparation products for sugarcane leaf in field.【Method】Medium with sugarcane leaf powder as the only carbon source was used to enrich cellulose-degrading bacteria of sugarcane leaf decomposition in field. Cellulose-degrading bacteria were preliminarily screened using Congo red medium and rescreened via determination of carboxymethyl cellulose （CMCase）activity，and according to analysis of morphological characteristics and 16S rDNA sequences，systematic taxonomic classification position of the screened bacteria were made clear. Weight loss rate of sugarcane leaves after fermentation treatment was analyzed and transmission electron microscope and scanning electron microscope were used to observe the change of sugarcane leaf ultrastructure， so as to make clear effects of the strain on sugarcane leaf degradation.【Result】 Through preliminary screening and rescreening，a strain of CMCase-producing strain XW005 with cellulase activity of 80.51 U/mL was obtained. According to analysis of 16S rDNA gene sequence and phylogenetic analysis，XW005 strain was identified as bacterium Brucella intermedia（NCBI accession number：MW538324.1）. Electron microscopic observation of sugarcane leaf microstructure showed that epidermis of sugarcane leaves under fermentation treatment of the strain cracked，while vascular bundles and plasma membrane disintegrated，the damaged leaves were loosened，the flat surface was destroyed，and the dense structure became loose. The results of sugarcane leaf degradation test showed that after 20 d of fermentation treatment，the weight loss rate of sugarcane leaves under the strain treatment reached 45.09%.【Conclusion】 XW005 is a bacterium capable of degrading cellulose and it can effectively degrade sugarcane leaves at room temperature， which has potential of development and prospect for application.