Valorization of food waste for cost-effective reducing sugar recovery in a two-stage enzymatic hydrolysis platform

The recycling of low-cost resources from waste biomass is a promising strategy towards circular bioeconomy. Food waste is an ideal candidate to produce cost-effective glucose. However several problems such as insolubility of macromolecular substances hindered the valorization of food waste. To recover reducing sugar efficiently, a two-stage enzymatic hydrolysis platform was developed, where the alpha-amylase was used at the first stage and glucoamylase followed. Results showed that the enzymatic hydrolysis was more efficient in comparison with acidic and alkali hydrolysis. The optimum pH and dosage for alpha-amylase and glucoamylase were determined to be 5.5 and 150 U/g total solid (TS), and 4.0 and 150 U/g-TS, respectively. The hybrid hydrolysis was more effective in catalyzing starch, obtaining the highest reducing sugar concentration of 204.2 g/L. Analysis of the physicochemical structures indicated that the solid particles could be broken thoroughly by the two enzymes, resulting in sharp decrease of the particle size and viscosity compared with the control. The mass balance and economic assessment verified the feasibility and profitability of the two stage enzymatic hydrolysis. The features of the two-stage platform widened the door to the further production of value-added biochemicals using the sugars recovered from food wastes.