Identification of a collagenase produced by Bacillus cereus R75E isolated from human colostrum

Recent studies have shown that the human colostrum and milk are a continuous supply of commensal, mutualistic and/or potentially probiotic bacteria to the infant gut. The diversity of complex bacterial communities in human milk can be used for the screening of novel bacteria with a potential interest for industry. Here, a protease-producing strain R75E was isolated from human colostrum and identified as Bacillus cereus based on its morphological, physiological and biochemical properties and molecular characterization. B. cereus R75E was found to produce 2 types of proteases with molecular weights of 106 and 95 kDa. Tandem mass spectrometry analysis has shown that both of these proteases belong to the 965-aa collagenase (GenBank accession no. KDB42252.1) of B. cereus. By PCR, the B. cereus R75E collagenase was identified just in the same DNA sequence as 965-aa collagenase. Its high sensitivity to EDTA verified that the enzyme is metalloprotease as expected by protein domain analysis. The present collagenase demonstrated high efficiency for the degradation of the native type I collagen, suggesting its potential applications to the degradation of animal organisms.