Bioassay for the rapid detection of bacteriocins in fermentation broth

A bioassay for the rapid detection of bacteriocins by detecting efflux of K + ions from a bacteriocin-sensitive indicator strain was developed. There w as a rapid increase in concentration of K+ in the medium from approximately 1.6 to 9.5 mM when the crude bacteriocin was added to the sensitive strain . A bacteriocin activity of 8.25 AU ml(-1) produced the lowest detectable c oncentration of K+ (0.179 mM) and the smallest inhibition zone (0.4 mm). Th e smallest cell dry mass of the indicator strain capable of releasing a det ectable level of K+ (0.102 mM) was 0.76 mg. Detection of the bacteriocin by measuring the efflux of K+ compares well with the conventional agar well d iffusion assay. Low activities of bacteriocin and low amounts of the sensit ive indicator strain biomass can be used with this bioassay.