Activity assay for nisin-like acidic bacteriocins using an optimal pH-conditioned gel matrix

Abstract

A new zymography for detecting nisin-like acidic bacteriocins was developed using a tricine–sodium dodecyl sulfate (SDS) gel and an acidic gel matrix (pH 4.0). After electrophoresis, proteins in the tricine gel were electrotransferred to an optimal pH-conditioned gel matrix (OP–CGM). The OP–CGM was overlaid with indicator cells (Bacillus cereus) embedded in nutrient broth soft agar (0.8%, w/v). Antibacterial activity shown as a growth inhibition using B. cereus was detected at approximately 3.8kDa. Because nisin is unstable in buffers at pH values over 6.0, the common electrophoretic systems, SDS–polyacrylamide gel electrophoresis and tricine gel, are not suitable for detection of nisin-like acidic bacteriocins.