Determination of the best nutrient medium for the production of L-lactic acid from beet molasses a statistical approach

Optimization studies have been carried out for the production of L-lactic acid from the fermentation of beet molasses by Lactobacillus delbrueckii. A PLACKETT -BURMAN Design and a Central Composite Design have been used to determine the most suitable nutrient medium for obtaining a maximum cell concentration. A second-order polynomial empirical model relating both the cell and nutrient concentrations was formulated. The variables selected for the study were Yeast Extract, Peptone, Tween 80 (antifoam), MgSO₄ · 7H₂O, MnSO₄·4H₂O, FeSO₄ · 7H₂O and K₂HPO₄/KH₂PO₄. Among them, only Yeast Extract and Peptone were found to significantly affect the cell concentration. A maximum cell yield was found when the concentrations of Yeast Extract and Peptone were, respectively, 5.31 g/l and 5.08 g/l. All conclusions are restricted to the experimental range studied.