(750c) A Novel Lactic Acid Species, Terrilactibacillus Tamarindi Sp. Nov., Enable to Produce Optically Pure D-Lactic Acid

Lactic acid is a versatile organic acid which contains the chiral properties, including L-isomer and D-isomer. Recently, lactic acid is emerged in the variety of applications; in particular, its demand is driven by rapid expansion of poly(lactic acid) (PLA) market. PLA is synthesized by polymerization of lactic acid and employed for various applications including packaging, cosmetic, and pharmaceutical industries due to its biodegradability nature. The lactic acid molecule has a chiral carbon that confers optical purity. It can be found in two different optical isomers including L(+)-lactic acid and D(-)-lactic acid. Highly optically pure lactic acid is required for the synthesis of high-quality plastic, and poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) are produced from L-lactic acid and D-lactic acid, respectively. Microbial fermentation has been extensively used as the major route for the synthesis of optically pure lactic acid. In comparison of L-lactic acid, the production of optically pure D-lactic acid has attracted to develop due to the demand for producing thermostable PLA, but large-scale production of D-lactic acid has not yet been commercialized. To date, the promising D-lactic acid-producing bacteria are recognized in the genus Lactobacillus and Sporolactobacillus, which represent a high level of D-lactic acid production and the optical purity with >99.5%. Additionally, the novel D-lactic acid producers, Terrilactibacillus laevilacticus was also reported as a potential strain to be used in industrial D-lactic acid fermentation. Later, previous screening studies in Thailand have isolated novel D-lactic acid-producing strains from bark of Tamarindus indica which could be identified as a novel species of Terrilactibacillus, namely Terrilactibacillus tamarindi sp. nov. The type strain is BCM23-1^T, identified as a gram-staining-positive, catalase-positive, facultative anaerobic, terminal-spore-forming rod and homofermentative bacteria. In this study, strain BCM23-1^T was examined the efficient D-lactic acid production under various fermentation conditions. Under anaerobic cultivation, strain BCM23-1^T showed a good fermentation performance in glucose medium (120 g/L) with a final concentration of 90.25 g/L, yield of 0.75 g/g glucose, productivity of 3.76 g/L·h, and optical purity of 100% D-lactic acid at 24 h fermentation time.