Enzyme for dairy processing: “microbial rennet” used in cheese making is most commonly produced by which microorganism group?

Introduction / Context:
Rennet substitutes used in cheese manufacture include microbial proteases that mimic the milk-clotting action of chymosin. Recognizing the common microbial sources of these enzymes is essential for dairy biotechnology and for understanding labeling such as “microbial rennet” on cheese packages.

Given Data / Assumptions:

• Microbial rennets are usually aspartic proteases.
• Species frequently cited include Mucor miehei and Mucor pusillus (zygomycetous molds).
• Other genera produce industrial enzymes, but not the classical “microbial rennet” used for clotting casein.

Concept / Approach:
The best-known commercial microbial rennets originate from Mucor species. These enzymes provide reliable milk-clotting, are produced at scale by fermentation, and are widely accepted for vegetarian cheese production. Although Aspergillus species produce many industrial enzymes, they are not the prototypical source for rennet used in cheesemaking.

Step-by-Step Solution:

Verification / Alternative check:
Product datasheets for microbial rennet often specify Mucor miehei or Mucor pusillus–derived enzymes, confirming the industry standard.

Why Other Options Are Wrong:

• Aspergillus spp: Important enzyme producers (amylases, proteases) but not the classical microbial rennet source.
• Bacillus spp: Yield neutral/alkaline proteases used in detergents/foods, not typical rennet substitutes.
• Saccharomyces spp: Yeasts for brewing/baking; not rennet producers.
• Penicillium spp: Important in cheese ripening (e.g., P. roqueforti), not rennet production.

Common Pitfalls:
Confusing ripening molds with clotting enzyme sources; assuming any protease works equally well—specific milk-clotting activity and low proteolysis on casein are critical.

Final Answer:
Mucor spp