Rowley, David C
Biomedical and Pharmaceutical Sciences
Formulation; Aquaculture; Probiotics; Microbiology; Shellfish; Natural Products
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Oyster production in Rhode Island accounts for over $2.5 million in annual revenue, making it the top aquaculture product in the state. However, larval tank infections significantly constrain production and create substantial economic losses for commercial hatcheries. In most cases antibiotics may not be used to prevent or treat larval tank infections. A probiotic, or beneficial microbe which competes with pathogens, is a safer and “green” approach to preventing infections. Vibriosis, a common cause of oyster larval mortality, is the result of Vibrio species infections. Previous studies have shown that a native Rhode Island microbe, Bacillus pumilus RI06-95, protects oyster larvae against infection by the pathogen Vibrio tubiashii RE22. In this study, a freeze-dried formulation of this probiotic agent was evaluated for use in commercial hatchery tanks. Stability, dispersion and pilot-scale hatchery studies were performed to evaluate this product. A viability analysis of the freeze-dried product over time revealed that when stored at 4 ºC, the product will maintain viable probiotic cells at greater than the minimum effective concentration, 108 CFU/mL per single-use tube, for at least two months. The dispersion of this product in seawater was investigated using light microscopy, and qualitatively showed that the product readily and rapidly disperses within 30 seconds, without any shaking or added energy. A pilot-scale hatchery study revealed that the freeze-dried product increased survival of three-day-old and eight-day-old larvae after challenged with Vibrio tubiashii RE22 by 26 % (± 15 %) and 47 % (± 28 %) respectively, compared to larvae which received no probiotic treatment. Based on these results, we conclude that our freeze-dried formulation of Bacillus pumilus RI06-95 is a stable, easy-to-use, safe and efficacious probiotic product for sustainable oyster aquaculture.