Harvesting BaCaseinase from Bacillus altitudinis 41KF2b for production of bovine casein hydrolysate with potential bioactivities

Recently, casein-derived hydrolases (BCH) have shown great potential for developing natural alternative treatments to treat metabolic syndrome. The present work aimed to isolate microorganisms that produce an extracellular caseinase from soil samples of rice root systems. The caseinase activity was determined by skim milk agar (SMA) assay. The BLASTn tool was used for phylogenetic analysis. The caseinase was purified by ammonium sulphate precipitation. The caseinase kinetics was determined to produce casein-derived hydrolases (BCH). The BCH revealed the antioxidant and the angiotensin I-converting enzyme inhibitory (ACE-I) activities. Our screening yielded caseinase secreted by a bacterial strain with 99% homology to Bacillus altitudinis 41KF2b called BaCaseinase. We then purified and determined the stability and kinetics of the BaCaseinase. It presented a Michaelis constant (Km) of 1.108 mg/mL, and a maximum velocity (Vm) of 21.27 × 104 U/mg at 45°C and pH 8. Next, we used the purified BaCaseinase to produce a bovine casein hydrolysate (BCH). The BCH showed three half-maximal inhibitory concentrations, including (IC50) of 0.60 ± 0.003 mg/mL for 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity, 0.13 ± 0.003 mg/mL for 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) scavenging activity, and 0.43 ± 0.002 mg/mL for ACE-I activity. The purified BaCaseinase is a heat-stable enzyme. This enzyme could digest bovine casein under multiple extreme conditions (an alkaline pH and a wide temperature range) to produce BCH that has both antioxidant and ACE-I activities. This enzyme shows promise for producing new hydrolysates, with the potential to treat metabolic syndrome.