PURPOSE:To obtain in high yield from culture solution serine protease having excellent characteristics by high-density culture of neutral and alkaline double protease defective strain under special conditions. CONSTITUTION:As a result of the study of high-density culture of neutral and alkaline double protease defective strain, culture of bacteria has been accomplished at a weight of =35g/l on a dry basis if the dissolved oxygen concentration is maintained at 0-5wt.% and glucose is added bit by bit to the system to diminish its concentration variation. The protease produced by the bacteria in the culture solution has a molecular weight of 44000-45000 determined by the gel filtration or SDS polyacrylamide gel electrophoresis technique, has an optimum active pH of 9-11 with casein as substrate, and has a N-terminated amino acid sequence of the formula.
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