Lactic acid production from food waste using the lactogenic Escherichia coli strain JU15: optimization of reducing sugar recovery

BACKGROUND d‐Lactic acid (DLA) has numerous industrial applications, including production of biodegradable polylactic acid, which is one of the most promising biodegradable polymers. Looking for alternative feedstocks is a high priority and recent focus has been on its biological synthesis and biotechnological valorization from food waste (FW) materials. In this study, a response surface methodology (RSM) approach and central composite design (CCD) were performed to hydrolyze FW, obtaining released reducing sugars (RRS) for DLA production using the lactogenic Escherichia coli strain JU15. RESULTS After an optimized sulfuric acid‐based pretreatment methodology using RSM and CCD, FW was utilized to obtain the maximum concentration of RRS, obtaining liquors containing glucose (85.59%), fructose (5.48%) and arabinose (8.92%) with an efficiency of ∼98% total sugar conversion from hydrolysis of FW. As the total sugar sources obtained titers of 26.85 ± 1.28 g L−1 (DNS) and DLA production was 22.66 ± 1.01g L−1, the DLA yield was 0.99 g g −1 total sugar. While arabinose was discretely consumed, with a remaining concentration of 0.36 ± 0.02 g L−1 after culture, the production of DLA through bacterial fermentation of the FW hydrolysates by the JU15 strain showed total depletion of glucose and fructose, achieving a maximum DLA production of 22.66 g L−1, with a maximum volumetric productivity of 0.73 g L−1 h−1 at 36 h. CONCLUSION This study provides an experimental optimization of a pretreatment to obtain released reducing sugars to lactic acid production from food waste as feedstock using the lactogenic E. coli strain JU15. © 2021 Society of Chemical Industry (SCI).