Aquaculture Reports (Jun 2023)
Evaluation of probiotic potentiality of GM-Lac (Lactobacillus and Bifidobacterium) in juvenile Asian seabass Lates calcarifer
Abstract
This study was conducted to evaluate the probiotic potentiality of GM-Lac (a mixture that comprises four lactic acid bacteria (LAB) strains– Limosilactobacillus fermentum GMNL-93, Lactiplantibacillus plantarum GMNL-141, Lacticaseibacillus casei GMNL-277, and Bifidobacterium lactis GMNL-550) applied in fish aquaculture. First, the four LAB isolates (GMNL-93, −141, −277, and −550) constituting GM-Lac were tested individually for antimicrobial activity in vitro. Then, GM-Lac was incorporated in fish feed at a dose of 5 × 106 cfu (g feed)−1 and fed to Asian seabass (Lates calcarifer) juveniles for eight weeks to assess the effects on growth performance, gastrointestinal (GI) histology and microflora, muscle amino acid composition, and disease resistance. According to the result of the zone of inhibition test, each GMNL strain presented noticeable antimicrobial activity against bacterial pathogens common in aquaculture. After the 8-week feeding trial, the fish in the GM-Lac group had higher final weight (p < 0.05), percent weight gain, specific growth rate, and feed intake than the fish in the Ctrl group, along with higher microvillus length in GI tract (p < 0.05) and greater total amino acid concentration in muscle. Furthermore, the relative abundance of microbial phyla in the GI tract of the fish fed with GM-Lac changed significantly, accompanied by increasing probiotic bacteria and decreasing pathogenic bacteria in the intestine and pyloric caeca. In the challenge test, the fish receiving GM-Lac all survived without any clinical symptoms when challenged with Streptococcus iniae. This study concludes that GM-Lac (the combination of L. fermentum GMNL-93, L. plantarum GMNL-141, L. casei GMNL-277, and B. lactis GMNL-550) is recommended as a probiotic supplement with high potential in aquaculture practice, which has antimicrobial activities against aquatic pathogens and benefits in enhancing growth performance, intestinal health, muscle amino acid composition, and disease resistance in juvenile Asian seabass.
