Abstract: Lactobacillus reuteri IMAU10240 is a potential probiotic lactic acid bacterium (LAB). This study aimed to achieve high viable counts of L. reuteri IMAU10240 by optimization of the composition of deMan Rogosa Sharpe (MRS) medium and culture conditions for industrialization application of this strain. The optimization was done using one-factor-at-a-time method, orthogonal array design and response surface methodology. The optimal medium composition was determined as follows (g/L): sucrose 100.00, soy peptone 13.25, yeast extract powder 8.84, yeast peptone 13.25, Na2HPO4 19.85, citric acid 2.58, MgSO4·7H2O 0.40, MnSO4·5H2O 0.12, glycerol 2.76, Tween-80 1.00, and L-cysteine hydrochloride 0.50, and the optimal culture conditions were 7–8 h culture at 37 ℃ and constant pH 5.5 under nitrogen atmosphere. In small-scale and pilot-scale experiments, the optimized conditions yielded a viable cell count of 7.57 × 109 CFU/mL, which increased to 2.59 × 1011 CFU/g after lyophilization. The enrichment medium and culture conditions can?be further verified in industrial production.

Key words: Lactobacillus reuteri, enrichment medium, high cell density fermentation