Ultrasound-Assisted enzymatic extraction of polysaccharides from agricultural By-Products: A comprehensive review

Polysaccharides are complex biopolymers of monosaccharide units linked through glycosidic bonds that serve roles in energy storage and diverse biological functions in living organisms. Agricultural by-products, including fruit peels, pomace, seeds, cereal brans, and plant residues, are abundant, renewable sources of bioactive polysaccharides with applications in the food, nutraceutical, and pharmaceutical sectors. These residual materials contain functional polysaccharides with antioxidant, immunomodulatory, prebiotic, and hypoglycemic properties. Conventional extraction methods have limitations, including prolonged processing times, excessive energy and solvent consumption, thermal degradation of heat-labile compounds, and scalability challenges. To address these constraints, ultrasound-assisted enzymatic extraction (UAEE) has emerged as a green extraction technology combining ultrasonic cavitation-induced mechanical disruption of plant cell walls with enzymatic hydrolysis for selective polysaccharide liberation. This review explains how enzyme-assisted extraction improves release by hydrolyzing cell-wall barriers (cellulase, hemicellulase, pectinase, and protease), often requiring optimized multi-enzyme cocktails and multivariate mixture designs to avoid antagonism. UAEE enhances extraction efficiency, reduces processing time, and operates under mild conditions that preserve structural integrity and bioactivity. Extraction performance is governed by the interplay of enzyme loading, pH, temperature, ultrasonic power, treatment time, and solid-liquid ratio, each of which displays a substrate-dependent optimum beyond which yield or structural integrity declines. Because the reported optima differ markedly with the botanical source and the target polysaccharide, they are best regarded as matrix-specific windows that require re-optimization for each feedstock rather than as universal set points. It evaluates UAEE applications, analyzes effectiveness across agricultural substrates, examines optimization methodologies, and discusses extracted polysaccharides, providing an overall sustainable framework.