Abstract:[Background] The development and screening of elite probiotics is the research hotspot of animal husbandry, and the potential function of probiotics has been extensively explored. [Objective] To isolate and screen the strains with good tolerance and high yield of extracellular protease and study their biological and enzymatic properties, so as to provide strain resources for the preparation of microbial protease and the development of microecological preparations. [Methods] Fresh feces samples were collected from healthy minks, from which the target strains were preliminarily screened with casein-containing medium and re-screened with optimized Folin method. The biological characteristics of the strains screened out were studied. The strains with high protease yield and good tolerance were obtained and identified by routine and molecular methods. Finally, the enzymatic properties of the protease were studied. [Results] A Bacillus strain with high protease yield and good tolerance was obtained and identified as B. subtilis (number 3). In the initial fermentation medium, the protease showed that the optimal reaction performance at 70 ℃ and pH 9.0, with the activity improved by K+ and inhibited by Cu2+ and Fe2+. In addition, 20% organic solvent did not deactivate the protease. [Conclusion] A B. subtilis strain with good biological characteristics, enzymatic characterization, and alkaline protease activity was isolated from mink feces. The findings of this study provide a basis for the production and application of this strain.
