Production of Extracellular Rennin-Like Enzyme by a Newly Isolate Mucor circinelloides (von Tieghem) and its Application in Camembert Cheese Making

Introduction: Aspartic proteases produced by different non-pathogenic fungi belonging to mucorales, are commonly used as milk-coagulants. The present study aims to optimize conditions for milk-clotting protease production by a new strain of Mucor genus and to assess its ability in soft cheese making. Materials and Methods: About 20 fungal strains isolated from soil were investigated for their potential to produce milk-clotting proteases for further applications in cheese making. The hyper producer strain Mucor circinelloides 2095-2047 was selected for optimization of rennin-like enzyme production under solid-state fermentation (SSF) using the stepwise modifications of the selected parameters. The enzyme produced under the optimal conditions was partially purified and then applied in Camembert cheese making trials compared to the crude extract and commercial rennet. Results: The maximum milk-curdling activity achieved after optimization (571.43 SU/mL) was obtained using wheat bran (10 g) as the mainly source of carbon containing 1% galactose; moistened with the M-9 solution (pH 6.0) and incubated at 30°C for 96 hours. The enzyme of M. circinelloides was partially purified with a high recovery of 105% and 6.23-fold purity after (NH4)2SO4 fractionation and dialysis. The physicochemical properties of the three produced cheeses were very close. A low sensory quality of cheese was obtained with the crude extract which was getting better using the pre-purified enzyme. This extract was able to develop a very close or even a similar sensory quality to that obtained by the commercial rennet. Conclusions: According to findings, it is possible to propose the purified enzyme of M. circinelloides as a new alternative for rennet, but further optimization, purification and cheese production tests are required.