Characterization of a novel protease from Bacillus cereus and evaluation of an eco-friendly hydrolysis of a brewery byproduct

Abstract

Proteases and proteolytic enzymes constitute one of the most important groups of enzymes and are attracting worldwide attention in attempts to exploit their physiological and biotechnological applications. In this study, partial purifications and biochemical and antimicrobial characterizations of a protease from Bacillus cereus spp., originally isolated from fermented cabbage, were carried out. The crude extract obtained after purification, involving ammonium sulphate precipitation and dialysis, was designated as a partially purified protease (PPP). The obtained PPP had a specific activity of 0.395-2.539 U/g at 32°C, with maximum activities for the fractions precipitated at 60 and 80% ammonium sulphate. The PPP activity ranged between 20 and 55°C, with an optimum temperature at 40°C. At 60°C, the PPP retained more than 30% of its activity. The optimum pH for the PPP was achieved at pH9, indicating the alkaline source of the enzyme. Protease production was specifically dependent on the calcium concentration in the culture medium. Also the robustness of the protease on brewer's spent grain hydrolysis was demonstrated. This suggests a potential eco-friendly application of the enzyme. Finally, it was found that the PPP inhibited the growth of Escherichia coli O157:H7. This novel property of the PPP liberated by the B. cereus spp. could provide important future benefits to industry.