Simplification and optimization of deMan Rogosa Sharpe (MRS) medium for enhanced production of bacteriocin by Weissella paramesenteroides DFR-8.

Abstract

Complex growth medium such as deMan Rogosa Sharpe (MRS) medium, commonly used for cultivation of fastidious lactic acid bacteria (LAB) interfere in bacteriocin purification. Sometimes all the ingredients of a defined medium are not required by all LAB strains for bacteriocin production. In the present study, composition of the MRS medium for the production of bacteriocin by Weissella paramesenteroides DFR-8, an isolate from cucumber (Cucumis sativus), was simplified and optimized with a step-wise strategy. In the first step, production profile, effect of incubation temperature, various C and N sources were investigated. In the second step, central composite rotatable design was employed to decide the optimal concentration of 3 key components (glucose, tryptone and pH) and the experimental results were fitted with a second order polynomial regression equation. According to the set criteria, the predicted bacteriocin titer from a medium containing 7.99% glucose, 9% tryptone, pH 7.5 (91.9% desirability) was 540 AU/ml and the observed bacteriocin titer was 538 AU/ml that indicated the validity of the developed model. Using optimized medium, bacteriocin titer of 674.5 AU/ml could be achieved after 72 h of fermentation that is nearly 2.5 fold higher than that obtained from unmodified MRS medium.