Optimization of Some Culture Conditions and Medium Composition for the Production of Bacitracin from Lactobacillus helveticus DF

Abstract

The objective of this study was to evaluate the effects of some culture conditions and components of the culture medium on the production of bacteriocin from Lactobacillus helveticus DF to get maximum bacteriocin yield. The results showed that the best culture conditions for maximum bacteriocin production were; pH 6, incubation temperature 37°C, incubation period 48 hours and the best culture medium MRS at anaerobic condition. Optimization of the medium ingredients was also investigated.The production of active antimicrobial peptide bacteriocin, active against Gram positive and Gram negative microorganisms including  P.aeruginosa (B) and  E. Feacalis (A), by L. helveticus DF isolated from feces of infants is influenced by complex nitrogen sources and carbon sources in the production medium. Medium components, especially pepton, beef extract and yeast extract, and their concentration contributed to increase in the production during the stationary phase. The Optimal nitrogen sources for their production were 1.5% , 2%, 2% (w/v) of pepton, beef extract and yeast extract respectively, accordingly, the present result evidenced that the increment in bacteriocin production was attributed with nitrogen source. Bacteriocin production by L. helveticus DF emphasized that, the higher bacteriocin yield was attained in the medium supplied with Tween 80 compared to medium without addition of tween 80, optimal concentration for their production 0.75%. Carbon source supplementation in culture media favored the maximum bacteriocin yield by L. helveticus DF, maximum bacteriocin yield when cultured in MRS supplemented with glucose and mannose (2%w/v). Bacteriocin production was affected differently by the presence of different concentrations of K2HPO4 or KH2PO4. Optimal bacteriocin production was recorded in the presence of 0.25% K2HPO4. The results of this study showed that the best production medium was named modified MRS medium which composed of 2% glucose, 2% mannose, 1.5% peptone, 2% yeast extract, 2% beef extract, 0.25% K2HPO4 and 0.75% tween 80, adjusted at pH 6 and incubated at 37°C for 48 hours (under anaerobic conditions) and with inoculum size of 4 % of cells number 1×109 cell/ml. After optimization, Bacteriocin activity was increase to 80 and 160 AU\ML against E. Feacalis (A) and P.aeruginosa (B) respectively.