Synergistic Effects of Microbial and Enzymatic Hydrolysis on the Growth Performance and Nutrient Utilization of BSF and Soybean in Macrobrachium rosenbergii: Mitigating Oxidative Stress and Enabling Metabolic Energy-Sparing

Abstract

The present study aimed to investigate the synergy effect of the use of BSF (Hermetia illucens) and SB (soybean) in combination as a fish meal and supplementing the feeding with microbial solid-state fermentation (MSF) using a co-inoculant of Rhizopus microsporus and Lactobacillus reuteri in feeding Macrobrachium rosenbergii. Sustainable BSF is limited by a tough, crystal-like alpha-chitin lattice responsible for damage to the structure of the intestine; SB harbors antinutritional properties causing systemic inflammation. The biological optimum was T6 (50% fermented BSF/SB and bromelain), which had the highest final weight (18.80 ± 1.26 g), specific growth rate (1.18 ± 0.17%/day), and feed conversion ratio (2.24 ± 0.30). FTIR spectra and SEM confirmed that fermentation was effective in reducing the chitinous matrix, resulting in an energy-sparing effect. This was manifested by a marked decrease in the endogenous secretion of protease from 6.88 ± 0.60 to 3.89 ± 0.14 mU/min/mg protein, with metabolic energy focused on somatic growth. However, the raw diets (T3 and T4) caused mechanical chitin abrasion and chemical irritations, which led to the highest level of MDA (3.18 ± 0.37μmol/g protein). T6 had the lowest oxidative stress (1.41 ± 0.04 μmol/g protein), and full replacement (T7) promoted metabolic overload and hyperlipidemia (73.53 ± 11.16 mg/dL triglycerides). In addition, fermentation promoted the integrity of the exoskeleton by generating prebiotic chito-oligosaccharides (maximum chitin yield 24.77 ± 2.15%). The results presented here confirm the potential of the 50% synergistic replacement approach, in combination with microbial and enzymatic bioprocessing, as a validated pathway for sustainable and efficient aquaculture.