Experimental design for optimization of D-lactic acid production using a UV-light selected strain

Abstract

Lactic acid is a molecule with several applications in different industries. Many applications require high isomeric purity, in order to attain the need properties of the final product. L-lactic acid production has already been extensively studied, however, D-lactic acid production remains a challenge since the majority of the strains used in lactic acid production are L producers. Bearing all this in mind, this study presents UV-light as an alternative tool to enhance D-lactic acid production. Different UV-light selected strains from Sporolactobacillus nakayamae subsp. nakayamae were studied in order to obtain high D-lactic acid concentration. Preliminary tests were performed using different carbon and nitrogen sources. Further, an experimental design was used to optimize the medium composition. As result, the selected strain presented a better D-lactic acid production compared to the natural strain, with 97% of isomeric purity. The maximal production of D-lactic acid reached 74.46g/L from clarified sugarcane juice and yeast extract, with a productivity of 3.10g/Lh.