Diets fermented by crab-derived lactic acid bacteria enhance growth, modulate the gut microbiota, and improve hepato-intestinal health in Eriocheir sinensis

Abstract

Proper fermentation of aquafeed using functional probiotics can enhance crustacean health and feed utilization. In this study, two crab-derived lactic acid bacteria (LAB) strains, Lactiplantibacillus plantarum MW 2406C and Lactobacillus brevis Myh YC-01, were used for feed fermentation. Furthermore, their effects on the growth performance, intestinal microbiota, and hepato-intestinal health of Eriocheir sinensis were evaluated. A total of 300 crabs (initial body weight: 75.53 ± 0.10 g) were randomly assigned to five dietary groups, with six replicates of 10 crabs each: non-fermented diet (NFD); sterile fermented diet (SFD), a basal diet fermented without bacterial inoculation and only added with sterilized broth and water; L. plantarum-fermented diet (PFD), a basal diet augmented with L. plantarum at 1 × 106 CFU/g; L. brevis-fermented diet (BFD), a basal diet augmented with L. brevis at 1 × 106 CFU/g; and mixture of fermented diet (MFD), fermented with L. plantarum and L. brevis in a 1:1 ratio, with a total bacterial concentration of 1 × 106 CFU/g. After feeding for 12 weeks, both the PFD and MFD groups had significantly higher digestive and antioxidant enzyme activities (P < 0.05). Moreover, the PFD and MFD groups showed upregulated expression of immune-related genes (hsp70, crustin, alf1, propo, toll1, toll2, and pelle) and intestinal barrier-related genes (pt, zo-1, and pm) (P < 0.05). Similarly, the absolute real-time quantitative PCR quantification and 16S rRNA sequencing analysis showed that fermented diets reshaped the gut microbiota by enriching beneficial taxa, suppressing potential pathogens, and increasing the detectable abundance of the supplemented LAB strains in the intestinal contents. This study also established a lipopolysaccharide (LPS)-induced model of crab enteritis to investigate the mechanisms by which the strains alleviate intestinal inflammation. The results revealed that fermented diets attenuated LPS-induced inflammatory responses by reducing the expression of inflammation-related genes (ilf2, litaf, and p38mapk) and restoring the expression of genes associated with the gut barrier (pt, zo-1, and pm), potentially by modulating the NF-κB and PI3K/AKT/mTOR signaling pathway. In conclusion, functional compound diets fermented with crab-derived LAB strains represent a promising and effective strategy for enhancing growth performance, modulating gut microbiota composition, and improving hepato-intestinal health in crab aquaculture.