Metabolic evolution of Lactobacillus pentosus for lactic acid production from raw glycerol

High costs are the bottlenecks of traditional lactic acid fermentation process using glucose and starch as raw material. Production of lactic acid from raw glycerol, a byproduct of biodiesel, can significantly decrease the costs of fermentation. Therefore, there is a need to overcome the disadvantages of low cell growth rate, biomass of strains, as well as low productive rate and yield of lactic acid. In this work, metabolic evolution of Lactobacillus pentosus R3-8 screened by our group was carried out by adding high concentration raw glycerol and lactic acid. The 60th generation evolved strain using raw glycerol, tolerated 130 g·L-1 raw glycerol, with 1.23 folds enhancement of biomass. The 50th generation evolved strain using lactic acid can tolerate 20 g·L-1 lactic acid with 18% increase in biomass. The growth curves of 60th generation evolved strain using raw glycerol cultivated in 5 L bioreactor indicated that the lactic acid concentration, yield and productivity were 45.0 g·L-1, 0.989 g·g-1 and 0.47 g·L-1·h-1, respectively. Fed-batch cultivation of 60th generation evolved strain using raw glycerol achieved 83.8 g·L-1 lactic acid, which was two folds of batch cultivation with the same strain. ©, 2015, Chemical Industry Press. All right reserved.