Isolation of a Duganella sp. of degrading cellulose bacterium at low temperatures and analysis of its degradation capacity

Abstract:

[Background] Low temperatures are one of the main factors limiting microbial degradation of straw returned to the field in cold regions. [Objective] To obtain the bacterial strains capable of degrading cellulose at low temperatures to improve the straw reutilization in cold regions. [Methods] The soil samples were collected in winter for strain enrichment with sodium carboxymethyl cellulose (CMC-Na) as the sole carbon source. The pure culture of the strain was obtained by the dilution-plate coating method, and the enzyme production conditions of the strain were optimized by single factor and orthogonal tests. [Results] A cellulose-degrading strain was obtained at 15 ℃ and identified as Duganella sp. The optimal enzyme production conditions of the strain were incubation with the liquid loading volume of 50/100 mL and inoculum volume of 12.5% at 15 ℃ and initial pH 7.0, under which the highest CMC enzyme activity was 398.2 U/mL, 40.45% higher than that before optimization. The degradation rates of filter paper, rice straw, and maize straw by the strain were 19.24%, 9.48%, and 7.30%, respectively, under optimal culture conditions. [Conclusion] This study provides new strain resources for straw degrading microbial resources in cold regions, as well as data reference for subsequent research on low temperature cellulose-degrading strains.

Key words:low temperature;cellulose degradation;optimization of enzyme production conditions