Efficient production of d-(−)-lactic acid from broken rice by Lactobacillus delbrueckii using Ca(OH)2 as a neutralizing agent

Effects of Ca(OH)2, NH4OH, and NaOH as neutralizing agents for efficient recovery of lactic acid was investigated. Lactic acid was produced from broken rice in a simultaneous saccharification and fermentation (SSF) process with Lactobacillus delbrueckii. Consumption of glucose (from broken rice) by the cells and the cell growth were the best with Ca(OH)2 among the three neutralizing agents used. Maximum productivities of lactic acid reached with Ca(OH)2, NH4OH, and NaOH were 3.59 g l−1 h−1, 1.51 g 1−1 h−1, and 1.40 g l−1 h−1, respectively. Ca(OH)2 reduced the lactate molarity of the fermentation broth, and thus resulted in the highest lactic acid productivity. Furthermore, it was apparently clear that divalent cation (Ca2+) was more effective in neutralizing the cultures compared to monovalent (Na+ and NH3+) cations.