Rennin‐like milk coagulant enzyme produced by a local isolate of Mucor

Among 20 isolates of Mucor isolated from various environments in Jordan and found to produce a rennin‐like acid protease, known as Mucor rennin‐like enzyme (MRE), Mucor J20 was found to produce the highest level of MRE. The optimum incubation conditions for enzyme production in a fortified wheat bran mixture using solid‐state fermentation were 3–4 days at 30°C. The highest MRE activity (185–200 rennin units or RU) was produced in a medium containing wheat bran and lentil straw (1 : 1 w/w) moistened with whey, and incubated in clay pots at 30°C for 4 days. A slightly lower activity value (178 RU) was found when using a mineral salt solution or distilled water instead of whey, or when using wheat bran alone with whey. At pH 4, the MRE retained its complete activity (100%) for 6 weeks at 5°C and 10°C, and for 3 and 2 weeks at 20°C and 30°C, respectively. After heating at 60°C for 10 min, the enzyme lost its activity at all pH levels used (pH 2–8). The crude extract of MRE was successfully applied in the manufacture of a cheese curd.