(529b) Efficient D-Lactic Acid Production By Sporolactobacillus Terrae SBT-1 from Alternative Carbon Feedstocks

Lactic acid is an important industrial product that is widely used in food, cosmetic, pharmaceutical, textile, leather, and industrial applications. Naturally, lactic acid is a chiral carbon compound which can be found in two different isomeric forms: L and D isomer. D-lactic acid has long been known as a precusor of the stereocomplex polylactic acid (PLA) which is a biodegradable polymer and mainly used in food packaging and many plastic utensils. With these advantages of D-lactic acid, increasing demand for lactic acid has been growing reported. Industrially, lactic acid is currrenly derived from bacterial fermentation. Nevertheless, lactic acid industry has the current limitations and challenges for cost-efficient microbial production of optically pure D-lactic acid. The main limitations to effective fermentation are regarded to the use of alternative fermentation substrates and unrealiability of the fermentation performance. To overcome these problems, the use of inexpensive fermentation substrate, such as cassava pulp hydrolysate, is highly recommened for developing of a cost-effective lactic acid production process. With the aim of this study, D-lactic acid production by S. terrae SBT-1 under the difference of two carbon sources was studied in flask cultures. Both carbon sources, cassava pulp hydrolysate (CPH) and cellulosic sugar BG (CBT BG), each at an initial concentration of 120 g/L, were used to evaluate the performance of SBT-1 for D-lactic acid production, compared with commercial glucose. The highest performance of SBT-1 for D-lactic acid production was obtained from the use of CPH as a carbon substrate with a maximum lactic acid titer of 108.16 g/L within 24 h of fermentation time, with a yield of 0.90 g/g, productivity of 4.51 g/L/h, and optical D-isomer of 99.12 %ee. Furthermore, increasing initial carbon substrate either CPH or CBT BG concentration at 240 g/L could promote lactic acid production of SBT-1 with a titer of 200.04 g/L and 190.05 g/L, yield of 0.84 g/g and 0.90 g/g, productivity of 4.17 g/L/h and 2.64 g/L/h within 48 h and 72 h, respectively. Additionally, evaluation of lactic acid fermentation performance by SBT-1 cultivated in sterile fermention medium containing different carbon substrates was also performed. The results revealed that heat-steriled media could influence the fermentation performance which was beneficial for lactic acid production of SBT-1. Furthermore, the present study could observe that an alternative generation of feedstocks in biotechnological production is sensitivity to the heat sterilization process, possibly accompanied by altering their chemical compositions contained in hydrolysate.