Lactic acid production from dining-hall food waste by Lactobacillus plantarum using response surface methodology

BACKGROUND: Food waste generally has a high starch content and is rich in nutritional compounds, including lipids and proteins. It therefore represents a potential renewable resource. In this study, dining-hall food waste was used as a substrate for lactic acid production, and response surface methodology was employed to optimise the fermentation conditions. RESULTS: Lactic acid biosynthesis was significantly affected by the interaction of protease and temperature. Protease, temperature and CaCO3 had significant linear effects on lactic acid production, while alpha-amylase and yeast extract had insignificant effects. The optimal conditions were found to be an a-amylase activity of 13.86 U g(-1) dried food waste, a protease activity of 2.12 U g(-1) dried food waste, a temperature of 29.31 degrees C and a CaCO3 concentration of 62.67 g L-1, which resulted in a maximum lactic acid concentration of 98.51 g L-1 (88.75% yield). An increase in inoculum size would be appropriate for accelerating the depletion of initial soluble carbohydrate to enhance the efficiency of alpha-amylase in dining-hall food waste fermentation. CONCLUSION: A suitable regression model for lactic acid production was developed based on the experimental results. Dining-hall food waste was found to be a good substrate for lactic acid fermentation with high product yield and without nutrient supplementation. (C) 2008 Society of Chemical Industry