Safety Evaluation of Milk-clotting Enzymes Produced by Aspergillus niger and Penicillium Spp through Solid State Fermentation for Cheese Production

Abstract

Milk-clotting enzymes (MCEs) play a crucial role in cheese production, facilitating the coagulation of milk, traditionally sourced from animal rennet. Soil samples were collected from Sidi Mamman Assarakawa and Sidi Akibu farms, while wheat bran was obtained from Sokoto Central Market. Fungi were isolated using serial dilution and cultured on Potato Dextrose Agar (PDA) with chloramphenicol (0.05 g/L). A potential milk-clotting enzyme (MCE)--producing fungi were screened using Skim Milk Agar, and the potential isolates that showed clear zones were identified based on macroscopic and microscopic characteristics using lacto-phenol cotton blue staining and subjected to solid-state fermentation using wheat bran as a substrate to produce MCEs. The crude enzyme extracts were evaluated for aflatoxin B1 content using ELISA. A total of 12 fungal isolates were obtained from soil samples collected from the dairy farms. Among them, two isolates (SMA 3 and SA 4) demonstrated significant proteolytic activity, forming clear zones of 8.0 mm and 6.0 mm, respectively. The isolates were respectively identified as Aspergillus niger and Penicillium spp with Aflatoxin B1 content of 7.1  0.02 from Aspergillus niger and 7.6  0.05 from Penicillium spp This study indicates the safe utilization of Aspergillus niger and Penicillium spp enzymes in solid-state fermentation for cheese production in Nigeria, providing a local and economically viable alternative in the dairy industry.