Thesis (M.Sc.)--Chulalongkorn University, 2015

Lactic acid has long been widely used in food and pharmaceutical industries. In addition, lactic acid is the major backbone in bioplastic industry. Unlike those available for existing markets, lactic acid for bioplastic is required to be low cost but high optical purity. With these constraints, one should develop the viable bioprocess that yield lactate at high production yield, rate, and optical purity. In this study, Bacillus aerolacticus BC-001, a potent lactic acid producing strain, was tested for simultaneous fermentation and recovery of lactic acid to further improve lactic acid production. It was found that with cell recycle to the fermentor during repeated batch culture with supplemented glucose, the fermentation process could be prolonged for another 39 h with increasing lactate titer and productivity up to 101.83 g/L and 11.8 g/L×h, respectively. Thus, this avoided the short cycle time in batch operation for lactate fermentation using B. aerolacticus BC-001 and eventually the production cost. Lactic acid was simultaneously recovered after discharged from the fermentor. After cell and protein separation were removed from the broth by filtration unit before the broth entered Amberlite IRA-400 anionic resin column where lactate was recovered from sodium lactate in the form of free acid. The broth containing sodium lactate was loaded at the flowrate of 2.0 mL/min and removed by 1 M HCl at the flowrate of 1.0 mL/min resulted in the total recovery percentage of 54.34%. The downstream lactate recovery units were successfully optimized to operate at the pH (6.0-6.5) and temperature (approximately 50 °C) similarly to those controlled in the fermentor to avoid chemical usage and high energy consumption. The findings from this study described the plausible process platform for simple yet efficient simultaneous lactate fermentation and recovery to the industrial level.