GROWTH MEDIUM OPTIMIZATION FOR BIOMASS PRODUCTION OF A PROBIOTIC BACTERIUM, LACTOBACILLUS RHAMNOSUS ATCC 7469

This study was undertaken to determine the glucose, yeast extract, tryptone and Tween 80 concentrations in a cultivation medium for optimal biomass production of a probiotic bacterium, Lactobacillus rhamnosusATCC 7469. Using response surface methodology, a central composite rotatable design was applied to allocate treatment combinations. A polynomial regression model containing linear, quadratic, cubic and quartic terms was used for analysis of the experimental data. Effects involving all four factors evaluated were found to be significant and the strongest effect was given by tryptone concentration. Estimated optimum conditions of the factors for the growth of L.rhamnosus were as follows: glucose=4.4% (w/v), yeast extract=6.0% (w/v), tryptone=6.0% (w/v) and Tween 80=1.1mL/L. The optimum-point medium gave higher counts of viable cells, specific growth rate and biomass productivity than de Man, Rogosa and Sharpe and the center-point media. Practical ApplicationsWith increasing demand for food products containing probiotic microorganisms from health-conscious consumers, there arises a need to establish effective fermentation techniques for probiotic biomass production. Medium formulation, fermentation parameters and fermentor design play important roles to ensure optimal results. This study highlights a statistical approach to optimizing medium formulation for a probiotic lactic acid bacteria strain, which is known for its high nutritional demands. The optimal medium formulation obtained from this study can be used for improving Lactobacillus rhamnosus fermentation as it is capable of producing more viable cells than de Man, Rogosa and Sharpe medium, which is generally recognized and used as a suitable medium for lactic acid bacteria cultivation.