Rennet, Microbial

Rennet, Microbial (nonpathogenic strain of Bacillus ce-reus) Produced as a white to tan, amorphous powder or a light yellow to dark brown liquid by controlled fermentation using Bacillus cereus. Soluble in water, but practically insoluble in alcohol, in chloroform, and in ether. Major active principle protease. Typical application used in the manufacture of cheese. 

Standard Preparation Use a standard-strength rennet, bovine rennet, microbial rennet (Endothia parasitica), or microbial rennet (Mucor species), as appropriate for the preparation to be assayed. Such standards, which are available from commercial coagulant manufacturers, should be of known activity. Dilute the standard-strength material 1 to 200 with water, and mix. Equilibrate to 300 before use, and prepare no more than 2 h before use. 

Rennet, Microbial (nonpathogenic strain of Bacillus cereus), 21 Rennet, Microbial (Endothia parasitica), 21... 

Rennet, Microbial (Rhizomucor (Mucor) sp.), 21 Erythrosine, 26 Ethone, 72... 

S3)21 Rennet, Microbial (Endothia parasitica), 132, 788, (S3)21 Rennet, Microbial (Rhizomucor (Mucor) sp.), 132, (S3)21 Rennet, Microbial (nonpathogenic strain of Bacillus cereus), 132,... 

Microbial rennets from a number of producers, eg. Novo Nordisk, Gist Brocades, and Miles, have been available since the 1970s and have proved satisfactory for the production of different kinds of cheese. Their price is considerably lower than that of chymosin. Their properties have proven very similar to those of chymosin (89,90), and only slight modifications of the traditional cheesemaking technique are required in practice. 

Animal Proteases. These include the pancreatic trypsins and the rennets, which are produced in both ultrapure and industrial bulk qualities. Again, the prospects for large increases in supply depend on the political and agricultural policies that control the production of livestock for slaughter. Currently, these enzymes cannot meet demand on a world basis adequately, with the result that the more price sensitive users have increasing interest in microbial enzymes. 

Microbial coagulants are now useful and are responsible for about one third of all the cheese produced worldwide, but suffer from the disadvantage of being too stable and so are threatened commercially by improved methods of produdng chymosin by recombinant DNA technology. The use of thermally destabilized microbial rennets results in residual enzyme levels in the milk product similar to or below those encountered when calf rennet is use (55). An unexpected benefit has been an increase on some occasions of the specificity of the microbial enzyme, making it virtually indistinguishable from the action of calf rennet. Also some microbial rennets help impart a flavor that is popular with consumers. 

Coagulant. Most of the coagulant is lost in the whey but some is retained in the curd. Approximately 6% of added chymosin is normally retained in Cheddar and similar varieties, including Dutch types the amount of rennet retained increases as the pH at whey drainage is reduced. As much as 20% of added chymosin is retained in high-moisture, low-pH cheese, e.g. Camembert. Only about 3% of microbial rennet substitutes is retained in the curd and the level retained is independent of pH. 

Branner-Jorgensen, S., Schneider, P. and Eigtved, P. 1980. A method of modifying the thermal destabilization of microbial rennet and a method of cheese making using rennet so modified. U.K. Pat. Appl. 2,045,772A. 

Prins, J. and Nielsen, T. K. 1970. Microbial rennet. Mucor miehei. Process Biochem. 5, 34-35. 

Vanderpoorten, R. and Weckx, M. 1972. Breakdown of casein by rennet and microbial milk-clotting enzymes. Neth. Milk Dairy J. 26, 47-59. 

Chymosin produces cheese free of bitter flavor and of excellent texture. The use of other acid proteases such as pepsin and many of the microbial rennets in the coagulation step often leads to bitter flavor and a soft texture after ripening. 

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