Characterization of protease activity of Lactococcus lactis species isolated from raw camel’s milk

Abstract

Background and Objective: The effect of physical and nutritional factors on the protease activity of lactic acid bacteria was evaluated by overlay assay under different temperatures, pH and modified growth medium. The aim was to find better conditions for the proteolysis of new indigenous lactic acid bacteria strains isolated from raw camel’s milk and this in order to develop new flavors for dairy products. Materials and Methods: Strains including Lactococcus lactis, Lactococcus cremoris and Lactococcus garviae were isolated from raw camel’s milk and screened for the optimization. Results: The results showed that Lactococcus strains had a good potential of proteolysis and that maximal protease activity occurrence was after an incubation period of 24 h at a temperature of 37°C and a pH of 7.2. Among the different carbon sources, lactose and glucose seemed to be the best for all Lactococcus strains. Likewise, casein and yeast extract revealed as the optimal nitrogen sources for best protease enzyme production for all the tested isolates. Furthermore, the association of glucose and yeast extract was good for protease activity but the one of lactose and casein was the best. Conclusion: Best protease activity of Lactococcus species isolated from raw camel’s milk was at 37°C after 24 h of incubation at pH 7.2 and in medium containing lactose (5 g L-1) with casein (5 g L-1).