Meta‐fermentation system with a mixed culture for the production of optically pure l‐lactic acid can be reconstructed using the minimum isolates with a simplified pH control strategy

Meta‐l‐lactic acid fermentation from non‐treated kitchen refuse was reconstructed using a combination of isolated bacterial strains under several pH control strategies. The meta‐fermentation system was successfully reconstructed using a combination of Weizmannia coagulans MN‐07, Caldibacillus thermoamylovorans OM55‐6, and Caldibacillus hisashii N‐11 strains. Additionally, a simplified constant pH control strategy was employed, which decreased fermentation time and increased production. The optimum pH (6.5) for the reconstructed meta‐fermentation was favorable for the respective pure cultures of the three selected strains. The l‐lactic acid production performance of the reconstructed meta‐fermentation system was as follows: concentration, 24.5 g L−1; optical purity, 100%; productivity, 0.341 g L−1 h−1; yield, 1.06 g g−1. These results indicated that constant pH control was effective in the reconstructed meta‐fermentation with the best performance of l‐lactic acid production at pH optimal for the selected bacterial growth, while the switching from swing pH control would suppress the activities of unfavorable bacterial species in un‐isolated meta‐fermentation. Graphical and Lay Summary The meta‐fermentation system was successfully reconstructed using a combination of three strains isolated from the compost. Additionally, a simplified constant pH control strategy was effective in the reconstructed system with decreased fermentation time and increased production of l‐lactic acid at the optimum pH (6.5) value, which was favorable for the respective pure cultures of the three selected strains. The reconstructed meta‐LA fermentation system proposed in this study increases organic biomass recycling efficiency.