Abstract:

[Objective] The aim of this study was to screen high-efficient cellulose-degrading bacterial and fungal strains suitable for use in northern China at room and low temperatures. [Method] Using sodium carboxymethyl cellulose medium, bacteria and fungi capable of degrading cellulose were isolated and preliminary screened from the samples of humus soil, rice straw, sheep feces and donkey feces collected from Inner Mongolia. The species of the obtained bacterial and fungal strains were molecularly identified by using 16S rDNA and ITS gene sequence analysis, respectively. The strains were further screened on cellulose Congo-red agar medium and by filter paper degradation test. 3,5-dinitrosalicylic acid （DNS） colorimetry was used to measure the cellulase activities of the strains. [Result] A total of 44 cellulose-degrading strains, comprising 43 bacterial strains and 1 fungal strain, were isolated. Of these, 27 strains were isolated at 30 ℃ and exhibited cellulose-degrading ability at room temperature, and 17 strains were isolated at 18 ℃ and exhibited cellulose-degrading ability at low temperature. At the genus level, Bacillus was the first dominant genus among room temperature cellulose-degrading bacteria, followed by Pseudomonas. Among low temperature cellulose-degrading bacteria, Pseudomonas was the first dominant genus, followed by Acinetobacter and Bacillus. A total of 35 strains with improved cellulose-degrading efficiency were subsequently identified using cellulose Congo-red agar medium and filter paper degradation test. Furtherly, 3 strains, T-8-2 （Bacillus spp.）, LF-7 （Bacillus spp.） and LF-5 （Aspergillus spp.）, with higher carboxymethyl cellulase （CMCase） activities were isolated by DNS colorimetry, with CMCase activities of （169.24 ± 2.18）, （136.79 ± 2.05） and （116.01 ± 0.52） U/mL, respectively. These 3 strains also had higher activities of β-Gase, FPA and C₁. [Conclusion] This study characterizes the community composition and cellulose-degrading ability of the culturable cellulose-degrading bacteria and fungi in Inner Mongolia. The screened 3 strains exhibiting cellulose-degrading ability at room temperature with high activities of CMCase, β-Gase, FPA and C₁ can be used as potential strains for effectively degrading cellulose in the development of fermentation agents for manure composting.

Key words: cellulose-degrading strain, room temperature, low temperature, isolation and screening, carboxymethyl cellulase activity