Apple Biomass Valorization Using Bacillus subtilis AY1 Pectinase: Optimization, Modeling, and Application

Abstract

Valorization of fruit-derived biomass requires efficient biocatalysts capable of converting pectin-rich residues into value-added products and improving downstream food-processing operations. Bacillus subtilis AY1, isolated from decomposed apples, was optimized for extracellular pectinase production, followed by purification, biochemical characterization, mathematical modeling, stability evaluation, and apple juice clarification. Optimization increased activity from 0.543 ± 0.015 to 1.453 ± 0.176 U/mL, corresponding to a 167.5% increase. Purification yielded 33.18 U/mg specific activity, 3.16-fold enrichment, 24.85% recovery, and an apparent molecular mass of approximately 32 kDa. Maximum enzyme activity occurred at 45 °C, pH 6, 50 min, and 2.5% pectin. Thermal response-surface modeling revealed a significant temperature × time interaction, while the enzyme retained 27% activity after 186 days at 4 °C. Apple juice treatment achieved 54.5 ± 0.2% transmittance and significantly increased reducing capacity and 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity. The novelty lies in integrating biomass-derived bacterial isolation, process optimization, mathematical modeling, enzyme stability, and food application. Future work should evaluate enzyme immobilization, scale-up, and valorization of pectin-rich agro-industrial residues.