Identification and characterisation of putative probiotic for use in aquacultured fish

• Main Author: Lim, Chiun Hao
• Other Authors: Loo Say Chye Joachim
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Science::Biological sciences::Microbiology; Engineering::Materials
• Online Access: https://hdl.handle.net/10356/156295
• Institution: Nanyang Technological University

The aquaculture industry is turning to the use of probiotics to promote good health among fish and improve their productivity. Among the different types of probiotics, host-derived probiotics promise improved efficacy towards specific fish species, compared to commercial or terrestrial-derived probiotics. Hence, to fully utilise the benefits of host-derived probiotics, this study aimed to identify and characterise potential probiotic strains of fish gut origin that can improve the disease resistance of Jade Perch, one of the newly farmed fish species in Singapore. Potential probiotics were isolated from the gut of five adult Jade Perches and tested for their antimicrobial properties against fish pathogens including Aeromonas sobria, Streptococcus iniae, and Streptococcus agalactiae. The final probiotic candidate was identified using 16S rRNA sequencing and Whole-Genome Sequencing. It was also characterised in terms of its biosafety and viability in different harsh conditions. The isolate that can inhibit the growth of A. sobria and S. iniae was identified to be Enterococcus hirae. It contains no virulence genes, antibiotic resistance genes, and mobile genetic elements. E. hirae presents good viability in environments of pH 3.0 and above, and with temperatures of 30°C to 45°C. It is found to be viable in simulated intestinal fluid, but not in simulated gastric fluid. The use of E. hirae as a probiotic for Jade Perch is promising as it is both safe and effective. More work is required, however, to explore suitable encapsulation techniques to protect the probiotic against a very low pH environment and gastric fluids. Future in vivo feeding trials are also recommended to test for its efficacy as a probiotic for Jade Perch under natural conditions.