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Influence of stirring speed, initial pH and fermentation time on obtaining microbial rennet from Rhizomucor miehei.

Abstract:

Chymosin is a protease (EC 3.4.23.4) that is required in the manufacture of cheese. Due to the high production costs of this enzyme, its obtention has been investigated in microbial fermentation processes, such as those generated by Rhizomucor miehei. Researchers have pointed out that this enzyme has a high milk coagulation activity and its production is affected by some operational parameters. Therefore, in this work, the effect of the agitation speed, the initial pH of the culture medium and the fermentation time in obtaining the microbial rennet produced by Rhizomucor miehei was studied. For this, a factorial 22 design completely random was selected, the initial pH (4.0 and 6.0), the agitation speed (200 and 300 rpm), the variation of pH, the glucose consumption and the enzymatic activity at 0, 24, 48 and 72 hours of fermentation were determined. The results showed that the highest enzymatic activity was obtained after 72 hours of fermentation with an initial pH of 4.0 and agitation of 300 rpm (p < 0.05). Likewise, it was determined that the interaction of the agitation speed, initial pH and fermentation time had a highly significant influence on the enzymatic activity (p < 0.01) and that there is no linear correlation between the rate of glucose consumption in the medium and the enzymatic activity obtained. Finally, it was observed that supplementing the medium with lactose decreased the coagulant activity of the milk’s protease enzyme.