Influence of washing on the valorization of fruit and vegetable waste by enzymatic hydrolysis

Half of the food produced in Europe for human consumption is thrown away. The transformation of residues derived from the agri-food sector into value-added products is an approach based on the circular economy that addresses this ethical, environmental and economic problem [1]. In this context, MixMatters project aims to valorize waste such as fruit and vegetable biomass (rich in complex sugar such as starch and cellulose) through a series of alternatives, including enzymatic hydrolysis. This study deals with the evaluation of the effect of a previous washing stage in the optimization of the enzymatic hydrolysis of this type of biomass generated in wholesale market (Spain). The experimentation was based on a previous test where it was observed that the high concentration of sugars (>70 g/L) in the starting sludge inactivated the catalytic capacity of the enzymes. After separation of the solid fraction by centrifugation, a glucose yield of 59% was obtained. As shown in Figure 1, the fruit and vegetable wastes were pretreated to obtain technically feasible feedstock. Dewatering was carried out in two steps by screw press and belt filter, and washing was carried out in three stages of centrifugation. In the optimization process, different enzyme activities were evaluated: gluco-amylase, α-amylase, cellulase, β-glucanase, pectinase, hemicellulase and endo-protease. Since washing was able to remove different hydrolysis inhibitors such as proteases, chelators, water soluble phenol generated during pretreatment [2], the type and amount of enzyme that maximized the release of sugars varied depending on the presence or absence of this step. Advancements in pretreatment and enzyme-assisted detoxification technologies have improved efficiency. However, there remains a need for cost-effective approaches that maximize sugar yield while minimizing inhibitory compounds, energy use, and enzyme consumption. References [1] Sánchez M. Laca A., Laca A., Díaz M. Clean-soil air water. 2021, 49 (8), 202000376. [2] Bhatia SK, Jagtap SS, Bedekar AA, et al. Bioresour Technol. 2020 Mar; 300:122724.