Sàng lọc các chủng vi khuẩn lactic từ ruột một số loài cá da trơn có tiềm năng sử dụng làm probiotic

Abstract

The research was conduted to isolate and screen acid lactic bacteria which had antimicrobial activity against pathogens Edwarsiella ictaluri and Aeromonas hydrophila causing Bacillary necrosis pangasius (BNP) and Hemorrhagic disease in cultured Tra catfish in the gastroinstestinal tracts of wild freshwater catfish. As the result, 96 strains of lactic acid bacteria (LAB) were selected which had inhibitory activity against indicator bacteria Escherichia coli with 29 strains isolated from Stripped catfish (Pangasius hypophthalmus (Sauvage, 1878)), 24 strains from Mystus nemurus (Valenciennes, 1839), 21 strains from Pangasius larnaudii (Bocourt, 1866), 12 strains from Clarias macrocephalus (Gunther, 1864) and 8 strains from Pangasius larnaudii (Bocourt, 1866). The result of gram staining and biochemical characteristic tests illustrated most of selected strains of lactic acid bacteria were gram-positive; spherical, oval, short rod or long rod shape; negative oxidase and negative catalase. Result from determination of antagonist activity and bacteriocin producing, there were 46 strains showed the inhibitory activity against A. hydrophia, 42 strains could inhibit E. ictaluri which were Gram-possitive, spherical or rod in shape and e specially, three strains of obtained LAB presented the antibacterial activities (produced bacteriocin) which all of them inhibited A.hydrophia and only one of three strains could inhibit E. ictaluri when the culture supernatants were neutralized to pH 6.5-7.0. Nucleotide sequences of their 16sRNA showed 100% (548/548bp) and 99% (551/552bp) homology to Lactobacillus reuteri HFI-LD5 CL2, CL 2.20, respectively and 100% (539/539bp) homology to Lactobacillus fermentum JCM- 1173 CT3.7.