关键词: 纤维素降解菌, 低温, 酶活性, 分离筛选, 芽孢杆菌, 假单胞菌

Abstract: [Objective] To screen low-temperature cellulose-degrading bacteria suitable for efficient composting of manure and straw in the Inner Mongolia region. [Methods] Using sodium carboxymethyl cellulose （CMC-Na） as the carbon source, bacterial strains were isolated and preliminarily screened from deciduous humic soil, naturally composted sheep manure, and cattle manure in Inner Mongolia under 18 ℃ culture conditions. Further screening was conducted using the cellulose Congo red degradation zone test, and the taxonomic identity of the isolates was determined via 16S rDNA sequence analysis. The filter paper strip degradation test was employed for additional screening of the isolates. The carboxymethyl cellulase （CMCase） activity of the screened cellulose-degrading strains was measured using the 3,5-dinitrosalicylic acid （DNS） colorimetric method. Finally, low-temperature strains with high cellulose degradation capabilities were obtained. [Results] Under 18 ℃ culture conditions, 30 cellulose-degrading bacterial strains were initially isolated. Following the cellulose Congo red degradation zone test, 15 strains with superior cellulose degradation abilities were selected, belonging to the classes Bacilli, Gammaproteobacteria, Actinobacteria, Flavobacteria, and Betaproteobacteria. Among these, Bacilli and Gammaproteobacteria were the primary dominant groups, with Actinobacteria as the secondary dominant group. At the genus level, Bacillus was the primary dominant genus, followed by Pseudomonas as the secondary dominant genus. Further screening of the 15 isolates using the filter paper strip degradation test yielded 7 strains with enhanced cellulose degradation capabilities. After culturing at 18 ℃, the CMCase activity of these strains was measured, identifying three highly efficient low-temperature cellulose-degrading strains: F-1-1 （Bacillus）, Y10 （Bacillus）, and T11 （Pseudomonas）, with CMCase activities of （29.25±0.98）, （20.73±0.27）, and （20.60±0.14） U/mL, respectively. These three strains also exhibited higher CMCase activity than other strains when cultured at 30 ℃. [Conclusion] This study elucidates the diversity and cellulose degradation capabilities of culturable cellulose-degrading bacteria in certain regions of Inner Mongolia under low-temperature conditions.The three low-temperature strains with high CMCase activity identified in this study represent promising candidates for the development of microbial agents for efficient low-temperature cellulose degradation in manure composting fermentation.

Key words: cellulose-degrading bacteria, low temperature, enzyme activity, isolation and screening, Bacillus, Pseudomonas