Optimized Co-Fermentation of Seed Melon and Z. bungeanum Seed Meal with Saccharomyces cerevisiae L23: Valorization into Functional Feed with Enhanced Antioxidant Activity

This study aimed to enhance the value of agricultural by-products by developing seed melon compound fermented feed (SMFF) using Saccharomyces cerevisiae L23. A two-stage optimization strategy was implemented. First, seed melon juice seed culture medium (SMCM) composition and fermentation conditions were optimized to maximize S. cerevisiae L23 biomass through single-factor and response surface methodology (RSM) approaches. The SMCM medium was optimized to contain 0.06% MgSO4·7H2O, 0.2% KH2PO4, 0.65% (NH4)2SO4, 0.1% pectinase, and 1.0% urea, and fermentation conditions with inoculation amount, fermentation time, fermentation temperature, and glucose addition were 6%, 28 h, 30 °C, and 0.5%, respectively. Furthermore, SMFF fermentation parameters were optimized via RSM, achieving S. cerevisiae L23 (10.35 lg CFU/g) and sensory evaluation score (83.1) at substrate ratio of 7:3 (seed melon juice: Zanthoxylum bungeanum seed meal), inoculation amount of 8%, and fermentation time of 36 h. Fermentation process significantly improved the nutritional profile of SMFF, increasing crude protein (13%) and vitamin C (VC) content (21%) while reducing neutral detergent fiber/acid detergent fiber (NDF/ADF) levels. SMFF also improved in vitro antioxidant capacity, with higher DPPH, ABTS, hydroxyl radical, and superoxide anion scavenging activities compared to SMFF control. This process efficiently valorized agricultural by-products into nutritionally enriched functional feed.