Screening and Identification of Gossypol-degrading Bacteria and Studies on Solid State Fermentation of Cottonseed Meal

Objective: The purpose of this study was to isolate bacteria capable of degrading gossypol and study their growth and degradation characteristics and detoxification effect on gossypol in cottonseed meal, which provided basis for further study on the mechanism of gossypol degradation by microorganisms. Methods: Gossypol acetate was used as the sole carbon source. A bacterium with gossypol degradation ability was isolated with dilution-plate method from soil samples collected from cotton producing areas in Shandong Province. The isolated bacterium was preliminarily identified by physiological and biochemical characteristics as well as 16S rRNA gene phylogenetic analysis. The degradation of gossypol in the solid-state fermentation of cottonseed meal was determined by high performance liquid chromatography. Results: A gossypol-degrading bacterium designated as YL01 was screened and identified as Raoultella sp. In addition to gossypol, this bacterium could also grow with catechol, protocatechuic acid and p-benzoquinone as the only carbon source. The rate of microbial degradation of gossypol was 48% when YL01 was grown in mineral salts medium with gossypol as sole carbon source for 10 d. The gossypol content in cottonseed meal decreased by 43% and the protein content increased by 10% within 8 d through solid-state fermentation. Conclusion: Raoultella sp. YL01 could degrade gossypol and show potential application value in eliminating gossypol in cottonseed meal by biological treatment technology.