Integrated hydrothermal pretreatment and enzymatic hydrolysis for optimal succinic acid production from the liquid fraction of municipal food waste

The mechanically extracted liquid fraction of food waste (LFFW) contains high carbohydrates levels making it a promising substrate for biobased succinic acid (SA) production. This study aimed to maximize the efficiency of SA production from municipal household and restaurant food waste, by creating a multistep LFFW valorisation strategy. Thus, a parameter-optimized protocol for integrated hydrothermal pretreatment (acid or alkali) together with enzymatic hydrolysis of the LFFW was created. The highest monosaccharides concentration of 66.2 g L⁻¹ was achieved using 4 % sulfuric acid at 180 °C for 0.5 h, combined with enzymatic hydrolysis with amylase, cellulase, and cellobiose. However, due to direct enzymatic hydrolysis of the LFFW (monosaccharides concentration of 56.9 g L⁻¹), it could immediately be used for SA production without requiring additional downstreaming processes due to inhibitors (i.e., furfural, formic acid, and acetic acid). Subsequently, the comparison of SA production efficiency of Actinobacillus succinogenes 130Z, Basfia succiniciproducens, and Actinobacillus succinogenes CICC11014, using the LFFW hydrolysate as feedstock, showed that A. succinogenes 130z, had the higher SA production efficiency with a yield of 0.43 g SA g⁻¹ glucose. Finally, a further process optimization was realized by nutrients addition (i.e. yeast extract, NaHCO₃, Na₂HPO₄·2H₂O, and K₂HPO₄·3H₂O), achieving a 54 % higher SA production yield compared to the LFFW fermentation without nutrients addition. These novel multistep strategy of LFFW utilization, provides key insights for future SA production in food waste treatment facilities.