Đánh giá tiềm năng probiotic của vi khuẩn phân lập từ hệ tiêu hóa của hàu Thái Bình Dương <i>Crassotrea Gigas</i> nuôi tại Ninh Hòa, Khánh Hòa, Việt Nam

Abstract

This study focuses on assessing the probiotic potential of bacteria isolated from the digestive system of Pacific oysters (Crassostrea gigas) cultivated in the Ninh Hoa region, Khanh Hoa, Vietnam, aimed at developing probiotic products for hatchery growth and depuration process of commercial oyster. Through isolation procedures using Marine agar medium, the research collected 22 bacterial strains from the oyster digestive system, comprising 15 gram-positive strains and 7 gram-negative strains. Criteria such as antibacterial activity, extracellular enzyme production, hemolytic activity, and salt tolerance were used to screen the bacterial strains for potential probiotic. Antibacterial activity against Vibrio parahaemolyticus and extracellular enzyme production (protease, amylase, cellulase) were evaluated using agar diffusion methods. Hemolytic activity was determined on Blood agar medium. Salt tolerance was assessed by measuring turbidity at a wavelength of 600nm. Following the screening process, three strains—BS2, N5, and N7—demonstrated resistance to Vibrio parahaemolyticus ATCC 43996, with salt tolerance up to 4% NaCl concentration, and exhibited extracellular enzyme production of protease, cellulase, and amylase. Furthermore, these three strains tested negative in hemolysis assays using blood agar plates. Upon 16S rRNA sequencing, N5 and N7 were identified as Bacillus cereus with a 100% similarity, while BS2 was classified as Enterobacter hormaechei with a 99.93% similarity.