Modulation of jade perch microbiota using encapsulated, host-derived microbial compositions

Abstract

The exacerbation of infection-related losses due to global warming and aquaculture intensification have necessitated effective mitigation strategies. Among these strategies, host-derived probiotics as a bio-remediation agent are promising to enhance fish disease resistance by competitively occupying adhesion sites, providing nutritional benefits, and producing antimicrobial substances that combat pathogens in the native environments of the probiotics. This research started by screening bacteria from the gut microbiota of Singapore’s newly farmed freshwater jade perch (Scortum barcoo). These isolates were evaluated for their efficacy against various freshwater pathogens, and their safety profiles were also thoroughly assessed to ensure their suitability for practical implementation. Considering the viability of probiotics in fish feed during storage and feeding is unreliable without encapsulation, selecting appropriate encapsulants becomes crucial for maintaining probiotic activity. Despite the importance of probiotic encapsulation, to the best of our knowledge, no reports have investigated the interactions between common encapsulants and the gut microbiota of aquacultured fish. This aspect has yet to be adequately addressed. This research looked into the metabolic interactions of widely used polysaccharide encapsulants with the gut microbiota of fish, focusing on evaluating the production of short chain fatty acids (SCFAs) and the effects on the composition of the gut microflora. The encapsulants with metabolic functionality were subsequently employed to encapsulate the probiotics, examining two encapsulation methods: needle extrusion and spray drying. The probiotics were effectively protected within the simulated gastric fluid (SGF) in both cases. At the same time, the spray drying method proved to be more successful in ensuring adequate release of the probiotics within the simulated intestinal fluid (SIF). This research demonstrated the framework for making informed decisions on the combination of probiotics and encapsulants tailored to specific fish species. This approach is anticipated to improve feed efficiency and overall productivity significantly. Further in vivo feeding trials will be required to assess the practical applicability of encapsulated probiotics in aquaculture.