Lactobacillus plantarum-derived α-amylase inhibitor significantly improves the physiological health and glucose metabolism of large yellow croaker (Larimichthys crocea) under a high-starch diet

This study aimed to investigate the effects of an α-amylase inhibitor (α-AI) produced by Lactobacillus plantarum M89, isolated from the intestine of large yellow croaker ( Larimichthys crocea ), on the growth and health of the fish. The α-AI, which showed 87 % stable inhibitory activity under high-temperature treatment, was supplemented into the diet at a concentration of 4 g/kg. After an 8-week feeding trial, the α-AI group exhibited significantly improved growth performance, including higher final body weight, weight gain rate, specific growth rate, and condition factor, alongside a lower feed conversion ratio. The inhibitor also enhanced liver glycogen content, upregulated key gluconeogenesis genes (glucose-6-phosphatase and pyruvate decarboxylase), and improved antioxidant status by reducing serum malondialdehyde and increasing superoxide dismutase and glutathione peroxidase activities. Furthermore, dietary α-AI improved liver and intestinal morphology, reduced viscerosomatic and hepatosomatic indices, and modulated intestinal microbiota. The α-AI group showed a higher survival rate after a bacterial challenge. The findings demonstrate that dietary supplementation with the L. plantarum M89-derived α-AI can enhance growth, antioxidant capacity, organ health, and potentially disease resistance in L. crocea . • Lactobacillus plantarum M89 was isolated from intestinal tract of healthy large yellow croaker. • L. plantarum M89 produces α-amylase inhibitor. • L. plantarum M89-derived α-amylase inhibitor improves growth and health of Larimichthys crocea .