Ultrasound-Assisted Hydrolysis of Food Waste using Glucoamylase: Statistical Optimization and Mechanistic Analysis with Molecular Simulations

Abstract

Food waste represents a promising and cost-effective resource for synthesizing value-added products through a fermentative pathway. Preceding fermentation, the hydrolysis of food waste into monomeric sugars is a crucial step. This study presents a comprehensive investigation of food waste hydrolysis, encompassing experimental and computational approaches, using glucoamylase (GLCM) enzyme. Initial optimization of hydrolysis parameters was conducted through the Box-Behnken design of experiments, resulting in a total reducing sugar yield (TRS) of 263.4 mg/g biomass under optimized conditions within 42 hours. Sonication of hydrolysis mixture at 35 kHz at 20% duty cycle, yielded a 4x reduction in hydrolysis time with 22% enhancement in TRS yield (320 mg/g biomass). Analysis of GLCMs secondary structure revealed sonication-induced changes through FTIR spectra deconvolution in both control and test experiments. Sonication led to a reduction in -helix content and an increase in random coil content. Molecular dynamics simulations, including molecular docking, unveiled the majority of amino acid residues associated with the GLCM binding pocket in the -helix and random coil regions. Consequently, sonication widened the binding pockets, facilitating easier transport of substrate and product. This effect translated into improved reaction kinetics in food waste hydrolysis. Research HighlightsO_LIStatistical optimization of food waste hydrolysis: TRS yield = 263.4 mg/g in 42 h C_LIO_LI4x reduction of hydrolysis time, 22% rise in TRS yield with 35 kHz sonication C_LIO_LISonication reduced -helix content & increased random coil content of glucoamylase C_LIO_LIMolecular docking simulation to deduce mechanism of ultrasound-assisted hydrolysis C_LIO_LIMD simulations reveal widening of binding pockets and enhancing catalytic efficiency C_LI