Response surface optimization of D(-)-lactic acid production from Lactobacillus SMI8 using corn steep liquor and yeast autolysate as nitrogen sources

Abstract

The production of D (-)-lactic acid from Lactobacillus LMI8 sp. was optimizated by central composite design, using two low-cost nitrogen sources: corn steep liquor (CSL) and yeast autolysate (YA). The fermentation were performed in 250 mL Erlenmeyer flasks containing 100 mL of production medium, maintained at 200 rpm and 37±1°C for 48 h. After data analysis by surface response method, it was revealed that Lactic acid production was significantly affected by the isolated CSL as well as the interaction between CSL and YA and the maximal production of D(-) lactic acid was 41.42 g/L – a value located at the central point, which corresponded to 15 g/L of CSL and 5 g/L of YA. Key words: D(-)-Lactic acid, Lactobacillus, Corn steep liquor, yeast autolysate, response surface methodology.