(655g) Keynote: High Performance of Sugar Utilization to Produce D-Lactic Acid By Sporolactobacillus Terrae SBT-1

Naturally, lactic acid occurs in two isomeric forms, i.e., L(+)- and D(-)-isomer, which can be utilized in numerous applications. In specific application, an optically pure lactic acid isomer has been desired. The production of optically pure L(+)- or D(-)-lactic acid can be achieved by the microbial fermentation, depending on the appropriate species and cultivation conditions. Although the technology of lactic acid production has long been developed, some limitations are being discussed, including substrate inhibition, yield and productivity reduction, end product inhibition, and decreased optical purity of lactic acid. Thereby, this study was encouraged to discover more potential microbe which presents the ability of lactic acid production with highly enantiomeric pure D(-)-isomer. The in-house bacteria isolate, Sporolactobacillus terrae SBT-1 was isolated from tree bark samples in Thailand. It was found as a potential D-lactic acid producer under batch fermentation using glucose medium (120 g/L) and anaerobic cultivation condition with mixing by presenting a final lactate titer of 120.9 g/L, yield of 1.00 g/g, productivity of 6.05 g/L·h and 100% D-lactate isomer. Interestingly, S. terrae SBT-1 exhibited an excellent performance of sugars utilization at high concentrations under batch culture with no exhibition of catabolite repression. The maximum lactic acid titer (190.5 g/L) was obtained when using the highest initial sucrose concentration (240 g/L) in the fermentation medium. Additionally, there is no by-products formation during the fermentation stage by S. terrae SBT-1. It should be noted that S. terrae SBT-1 can be accounted for further advantages.