Studies on the Production of Microbial Rennet by Solid State Fermentation

Abstract

Due to acute shortage of calf rennet in recent years fungal rennets have received wide acceptability as calf rennet substitutes. A potent strain of Mucor miehei, a thermophilic fungus, was cultivated under Solid State fermentation conditions for the first time. The effect of some important nutritional parameters on the first time. the effect of some important nutritional parameters on the production of milk clotting activity was investigated. Milk clotting enzyme also known as acid protease is obtained from fungi and is similar to either pepsin or chymosin. Chymosin is the main milk clotting component of the calf rennet or rennet extract. It is known that the action of chymosin on kappa casein of milk is primarily responsible for the formation of cheese coagulation (Anstrup 1980). Studies were conducted in submerged fermentation conditions and found that rennet production on solid state fermentation was cheaper than produced in submerged fermentation. The proteolytic activity of rennet produced in submerged fermentation and solid state fermentation was also compared, and reported that rennet produced on solid state fermentation was having less proteolytic activity than the submerged grown culture. The effect of some important nutritional parameters on the production of milk clotting activity was investigated. Six complex type carbon sources were tried and wheat flour at 90:10 ratio gave a milk clotting activity of 34000 SU/g of dry moldy bran. Among the inorganicand organic nitrogen sources tried, organic sources favored higher enzyme production. The maximum milk clotting enzyme activity obtained was 58,000 su/g. The euzyme had a high ratio of milk clotting to proteolytic activity comparable to the commercial fungal rennets in the market. The cheese prepared from the enzyme was favorably evaluated in organoleptic tests.