Characterisation of crude bacteriocin produced by Pediococcus pentosaceus 2A2 in enriched molasses medium

The objectives of the present work were to determine the optimal molasses concentration as carbon source in enriched molasses medium for bacteriocin production by Pediococcus pentosaceus 2A2, and to evaluate the characteristic of bacteriocin produced. Enriched molasses medium was based on MRS (de Man Rogosa and Sharpe) broth, and molasses was used instead of glucose as carbon source. Bacteriocin production was performed in enriched molasses media containing various molasses concentrations (10% to 50%) added with 0.5% meat extract, 3% yeast extract, 1% peptone, Tween 80 and minerals, and incubated at 37°C for 24 h. The cellfree supernatants (CFS) of the culture were further examined for antibacterial activities against Listeria monocytogenes ATCC 7644, expressed as the diameter of inhibition zone using the disc diffusion method. The results showed that CFS produced in medium containing 30% molasses demonstrated high antibacterial activity but was not significantly different as compared to the control medium. The CFS was then precipitated using gradient concentration (20% to 90%) of ammonium sulphate, centrifuged (12,000 g, 15 min, 4°C), followed by dialysis through 2.0 kDa cut off membrane to obtain crude bacteriocin for characterisation study. Crude bacteriocins produced in enriched medium containing 30% molasses and MRS broth were stable either to heat treatments (30 min at 80°C, 15 min at 100°C and 121°C) or pH (2.0; 4.0 and 6.0). The present work gave evident that molasses have the potential to be used as low-cost component for bacteriocin production by P. pentosaceus 2A2. In addition, as compared to sodium benzoate and sodium nitrite, the antibacterial activity of crude bacteriocin against tested bacteria was also significantly higher, indicated that it may be promising to be applied in food.