Monitoring the Degradation of Commercial Microbial Rennet Preparations

Abstract

Fractionation on a DEAE-Sephadex A-50 column was used to study the degradation of microbial rennets derived from Mucor miehei. A comparison was made between the crude culture filtrate, derived from the growth of the microorganism in submerged culture condition on wheat bran medium, and commercial preparation Marzyme and Rennilase. The elution protein profiles lacked some of the peaks associated with the crude culture filtrate however, the milk-coagulating activity eluted out at approximately the same NaCl molarity (.45 M). Each brand name product had a characteristic elution pattern, which did not vary between their thermostable and thermolabile enzyme preparations. With storage at 4°C the elution protein profiles of the thermolabile enzyme preparations changed in a distinctive manner characteristic of the brand name. With the Marzyme series, the milk-coagulating activity eluted out at the same NaCl molarity, whereas other established peaks increased in area. The milk-coagulating activity, from Rennilase, eluted from the column at a lower NaCl concentration (.35 M). The changes were evidence of enzyme degradation, which was manifested by a general decrease in specific enzyme activity. By using column chromatography it was possible to monitor the stages of degradation with time. © 1989, American Dairy Science Association. All rights reserved.