Abstract:

MRS medium for Lactobacillus reuteri is an enrichment medium. It is essential for industrial fermentation to simplify medium composition and optimize selected constituents and culture conditions. Based on traditional MRS medium, nitrogen sources were optimized through single factor experiments. Plackett-Burman and central composite designs were then used to optimize medium and cultureconditions for exploring the growth of L. reuteri CG001. Finally, the growth metabolism of L. reuteri CG001 was investigated under optimized conditions. Results indicated that the concentrations of yeast extract, glucose, manganese sulfate and culture temperature were the most important factors affecting the growth of L. reuteri CG001. According to response surface analysis, the optimal conditions were 20 g/L yeast extract, 20 g/L glucose, 7 g/L sodium acetate, 1 g/L ammonium citrate, 3 g/L K2HPO4, 0.2 g/L magnesium sulfate, 0.23 g/L manganese sulfate, 1 g/L Tween-80, initial pH 6.2, and culture temperature of 38.6 ℃. The final cell amount reached up to 0.984 g/L under the optimal conditions, which exhibited 1.102-fold improvement. An “S”-shaped pattern of the growth curve for L. reuteri CG001 in fermentor was observed. Cell growth was at the logarithmic phase during the period of 4－12 h, followed by a balance state between glucose metabolism and cell growth.

Key words: Lactobacillus reuteri, Plackett-Burman, central composite design, response surface methodology, optimization