Abstract: 【Objective】 To identify and verify the functions of the multifunctional straw-degrading strain LF-4,addressing issues such as slow straw decomposition,excessive residue,and potential threats to subsequent crops during the process of straw returning to the field.【Methods】 Strain LF-4 was isolated from rapeseed straw. Its cellulose-degrading capability was measured using the Congo Red staining method,aniline blue decolorization method,and filter paper disintegration assay. The strain was identified through morphological and molecular biological methods. Its cellulase activity and straw degradation capability were determined. The growth-promoting,antagonistic,and phosphate-solubilizing functions of the strain were verified using the salkowski colorimetric method and the plate confrontation assay.【Results】 Strain LF-4 exhibited robust cellulose-degrading capacity and was identified as Bacillus velezensis. Its peak cellulase activity reached 207.45 U/mL,and the indoor degradation rate of rapeseed straw reached 53.04% after 30 d of liquid fermentation. Strain LF-4 demonstrated growth-promoting,phosphate-solubilizing,and protease-producing functions,with an indole-3-acetic acid （IAA） yield of 10.26 mg/L,and displayed a broad antimicrobial spectrum,with a maximum inhibition rate of 67.19%.【Conclusion】 The core characteristic of B. velezensis LF-4 is the strong cellulose-degrading capability,and it also possesses growth-promoting,antagonistic,and phosphate-solubilizing functions.

Key words: Straw, Degrading strain, Cellulose degradation, Growth-promotion, Bacillus velezensis