| Summary: | In the paper, the fermentation conditions and fermentation medium of bacillus subtilis protease production were optimized to improve the outcome of the protease produced from bacillus subtilis to provide premium raw materials for the subsequent preparation of chitin from crab shell. The optimal fermentation conditions are temperature at 39°C, pH value of 7.5, fermentation time of 60h, inoculum size of 5%, filling volume of 80/250mL, and rotational speed at 180r/min; the optimal medium component ratio is 1.25% for starch mass concentration, 1% for yeast paste mass concentration, and 0.3% for sodium dihydrogen phosphate mass concentration. The activity of protease produced from bacillus subtilis GC021 is 174.87U/mL under the optimal fermentation conditions and at the optimal medium component ratio.
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