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Proteolytic enzymes from fermentation of fish plant wastes Wah-On, Howard Christopher

Abstract

A clarified, nonheat coagulable fish medium derived from condensed fish solubles (B.C. Packers, Richmond, B.C.) was explored for its potential use as the major component of a fermentation medium for the production of proteolytic enzymes. The organism used was a pure strain of Sorangium. Factors affecting the bacterial metabolic activity and consequently the rate and extent of protease formation were studied. Statistically designed experiments showed that both calcium and glucose had a significant effect on growth and protease formation, the latter supplementary nutrient being the more influential. Of the six carbohydrate sources (glucose, mannose, galactose, xylose, arabinose, and soluble starch) tested, only glucose and mannose were utilized for further growth. Neither initial pH (in the range 4 to 8) nor inoculum age (16 to 24 hrs) significantly affect the maximum yield of protease. Kinetic studies with the optimum medium in 250 ml Erlenneyer flasks and in a 7-litre fermentor revealed that growth was biphasic with an initial fast growth followed by a slower secondary growth. The staged growth was attributed to the initial, fast utilization of easily available nutrients (such as amino acids) originally present in the medium, followed by a second, slower reaction in which the larger polypeptide units in the medium were digested. Since the inflection in the growth curve was entirely eliminated by increasing the agitation and/or aeration rate(s), it was thought that dissolved oxygen concentration and rate of oxygen transfer might be the rate limiting factors. Kinetic analysis of the data showed that product formation was not associated by any direct mechanism with carbohydrate utilization. Protease formation was highest with an agitation rate of 500 rpm and an aeration rate of 2 litre of air per minute, which corresponded to an oxygen transfer coefficient of 0.805 millimoles O₂/atm. min. l. Recommendations for further work are suggested.

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