Growth medium optimization using response surface methodology for a probiotic bacteria, lactobacillus rhamnosus ATCC 7469

Abstract

Response Surface Methodology was used in this study to optimize the fermentation medium for a probiotic microorganism, Lactobacillus rhamnosus ATCC 7469. The response was the growth of L. rhamnosus, represented by log 10 (the number of viable cells ml/'} and the jour factors evaluated were glucose, yeast extract, triptone and Tween 80. A central composite design was used as an experimental design for the allocation of 31 treatment combinations. A polynomial regression model with cubic and quartic terms was used for analysis of the experimental data. An optimized medium formulation was produced from the model Y = 9.62 + 0.1 1XI- 0.07X2 + 0.10X3 - 0.05X/ - 0.02X/ + 0.06X/ - O.OlX/ + 0.05XIX2 - 0.09XIX3 + 0.04XjX, + 0.03X2X3. The optimum-point medium comprised 4.4% (w/v) glucose, 6.0% (w/v) yeast extract, 6.0% (w/v) triptone and 0.11% (v/v) Tween 80. A validation test which was carried out to compare the growth of the bacteria in the optimum-point medium, de Mann, Rogosa, Sharpe (MRS) medium and center point medium showed that growth in the optimum- poillt medium produced the largest number of viable cells.