Enzymatic Hydrolysis of Cellulose and Proteins in Spent Coffee Grounds

Abstract

This study investigated the enzymatic hydrolysis of polysaccharides and proteins in spent coffee grounds (SCG) to enhance bioavailability and digestibility for potential food additive applications. Using Viscozyme® L, a commercial lignocellulosic enzyme cocktail, the research explored how process modifications impact enzymatic efficiency. Two pre-treatments were examined: Alcalase® (a protease enzymatic pre-treatment) and particle size fractionation (a physical pre-treatment). Apparent Michaelis-Menten kinetics were employed to model enzymatic reaction kinetics in these insoluble systems. The effects of enzyme/substrate ratio on polysaccharide hydrolysis efficiency were systematically evaluated at the manufacturer's recommended pH and temperature. The study was conducted at 50°C, pH 4.8, with varying enzyme loadings and a reaction time of 24 hours. Results showed that particle size reduction through fractionation achieved the highest degree of hydrolysis (27.87%) and sugar yield at a Viscozyme® L loading of 0.01mL/g, highlighting its potential for industrial applications. Alcalase® pre-treatment demonstrated a moderate improvement in lignocellulose hydrolysis efficiency, likely due to increased accessibility of carbohydrates to enzymes following protein structure breakdown. Kinetic modeling revealed that smaller particle sizes resulted in higher reaction rates and lower apparent Km values, indicating improved enzyme-substrate interactions. The research demonstrates the potential of SCG as a valuable resource for the food industry, offering a pathway to valorize this abundant waste stream.