Plant ash modulates enzymatic hydrolysis of food waste for bioactive polysaccharide recovery

Existing food waste (FW) treatments, e.g., composting and anaerobic digestion, could enable nutrient and energy recovery, whereas the selective recovery of high-value bioactive polysaccharides (BPS) from FW has received limited attention. The alkaline nature of plant ash (PA) may regulate FW hydrolysis process and favor BPS accumulation, but this potential remains unexplored. In this study, a PA-modulated enzymatic hydrolysis strategy was developed to enable targeted BPS recovery. PA-modulated enzymatic hydrolysis increased the BPS yield from 2.29 ± 0.07% to 7.73 ± 0.14% (w/w), representing a 2.38-fold increase over enzymatic hydrolysis alone. Combined analyses revealed that PA-regulated pH selectively attenuated glucoamylase-driven terminal saccharification while preserving α-amylase-mediated polysaccharide release, thereby redirecting enzymatic hydrolysis toward BPS preservation. The recovered BPS at 2.0 mg/mL exhibited excellent antioxidant activity, achieving scavenging efficiencies of 54.46 ± 3.28%, 86.33 ± 2.14%, 43.93 ± 1.20%, and 41.01 ± 1.77% against DPPH, ABTS, •OH, and •O₂^- radicals, respectively. Furthermore, incorporation of the recovered BPS into polyvinyl alcohol (PVA) significantly enhanced the tensile strength (36.89 ± 1.56 MPa) and UV-A shielding efficiency (89.42 ± 0.33%) of biodegradable composite mulching films, demonstrating its potential as multifunctional bio-based additive for sustainable agricultural materials. This work established a novel strategy for selectively recovering BPS from FW for sustainable FW valorization.