Antimicrobial activity and partial characterization of bacteriocin-like inhibitory substances (BLIS) produced by Bifidobacterium infantis BCRC 14602

Bifidobacterium infantis BCRC 14602 was found to produce a bacteriocin-like inhibitory substance (BLIS) with inhibitory activities against a wide range of Gram- positive and Gram-negative bacteria. An activity level of 400 AU/ml in the middle of the exponential phase (i.e. 6 h) and maximum activity (1600 AU/ml) at the beginning of the stationary phase (i.e. 16 h) was recorded in MRS broth at 37 °C. BLIS was partially purified by a two-step purification protocol resulting in a specific activity of 31,605 AU/mg and a purification fold of 120. Based on Tricine–SDS–PAGE, the BLIS is approximately 3.0 kDa in size. Complete inactivation of BLIS activity was observed after treatment with proteolytic enzymes, but not with catalase, α-amylase and lipase. The adsorption of the BLIS to the producer cells was strongly affected by the pH of the broth culture of which 100% adsorption to the killed cells occured between pH 6.0 and 7.0, whereas at pH values below 6.0 and above 7.0, the adsorption ratio decreased to 43 and 60%, respectively. BLIS showed high temperature stability up to 121 °C for 15 min with no loss in its activity, and had pH stability in the range of 4–10. The temperature and heat stability of BLIS makes it useful for applications in food processing technologies and food safety control applications.