Response Surface Methodology (RSM) was used in the study to optimize the production of vanillin from isoeugenol through fermentation by Aspergillus niger I-1472. Three factors were studied which include amount of isoeugenol, resin (Amberlite XAD-4) and Span 80. During fermentation, isoeugenol as substrate were vortexed with Span 80 and added into the culture on Day 4. Resin (Amberlite XAD-4) was added into the medium the following day. The predicted optimum medium combination consisted of 3.61 g/L of isoeugenol, 5.8% (g/ mL) of Amberlite XAD-4 resin and 0.37% of Span 80 with an expected vanillin production of 0.137 g/L. Verification test showed that the model produced similar predicted and experimental values.
This study was undertaken to optimize yeast extract, glucose, and vitamin concentrations; and also culture pH for maximizing the growth of a probiotic bacterium, Lactobacillus rhamnosus, and to assess the effects of these factors by using response surface methodology. A central composite design was used as an experimental design for the allocation of treatment combinations. A polynomial regression model with cubic and quartic terms was used for analysis of the experimental data. It was found that the effects involving yeast extract, glucose, vitamins and pH on the growth of L. rhamnosus were significant, and the strongest effect was given by the yeast extract concentration. Estimated optimum conditions of the factors for the growth of L. rhamnosus are as follows: pH=6.9; vitamin solution=1.28% (v/v); glucose=5.01% (w/v) and yeast extract=6.0% (w/v).