An innovative temperature control strategy to improve optically pure L-lactic acid production from food waste

Abstract

Fermentation of food waste to lactic acid (LA) is a strategy for resource recovery. However, the poor yield and optical activity (OA) of L-lactic acid (L-LA) are major bottlenecks for such efforts. This study focuses on enhancing L-LA yield and optical purity from the food waste without sterilization and inoculation at pilot-scale. First, the effects of temperature on LA production were explored. A higher LA yield but lower purity was obtained under mesophilic conditions, whereas the opposite results were represented at high temperature. On the basis of these findings, a novel two-stage temperature regulation strategy was developed that combined the benefits of both temperature conditions. This strategy not only ensured a L-LA yield of 0.371 g/g volatile solid, but also achieved a high optical purity of 98.0%. The underlying mechanism is that high temperature could enrich L-lactic acid bacteria (LAB) and inhibit LAB producing both L- and D-LA. Overall, this innovative strategy may be well-suited for generating optically pure L-LA from food waste fermentation.