Optimization of lactic acid production from tea waste by Lactobacillus plantarum MTCC 6161 in solid state fermentation by central composite design

The present study investigates the potential use of tea waste for the production of lactic acid using Lactobacillus plantarum MTCC 6161.The tea waste comprise of tannin, which acts as a carbon source, which upon microbial activity gets converted to glucose. In this study, initially the effects of four process variables namely yeast extract concentration, moisture content, substrate concentration, and (NH4)2SO4 concentration were studied using fractional factorial design (FFD). From FFD it was found out that yeast extract concentration, moisture content and substrate concentrations had statistically significant effect on lactic acid concentration in the final product. Consequently, these variables were optimized through response surface methodology. A central composite design was used for this purpose. A quadratic model was proposed to predict the lactic acid concentration. Maximum lactic acid concentration was achieved when amount of yeast extract , amount of substrate (tea waste) , and moisture content were 0.2 g, 11 g and 80% respectively. Corresponding lactic acid concentration was estimated to be 13.82 g/L. The results thus suggest that tea waste, otherwise waste, can be used to produce lactic acid.