Isolation of potential probionts from brackishwater enriched with high levels of carbon source

Abstract

The majority of shrimp producers utilize probiotics derived from terrestrial sources as part of their aquaculture management. The beneficial effects of terrestrial probiotics on shrimp may be affected due to environmental differences between the cultivated species and the source of the probiotics. To ensure maximum effects on the host, it is essential to use probionts derived from the host or the environment of the cultured organism. Consequently, the objective of this study was to isolate and characterize potential probionts from brackishwater by enriching the water with organic sources containing a high ratio of carbon to nitrogen (C:N). Six 10-li containers were filled with brackishwater from an estuary for a mesocosm experiment. To stimulate bacterial growth, water was enriched with either molasses or brown sugar at a C:N ratio of 15. After twenty days, all heterotrophic bacteria in the enriched water were enumerated. The <i>in vitro</i> antagonistic activities of distinct bacterial colonies against <i>Vibrio harveyi</i>, a crustacean pathogen, were evaluated on fresh Nutrient Agar plates containing 1% sodium chloride. There were 10 bacterial isolates with <i>in vitro</i> antibacterial activity. These bacterial isolates are categorized as belonging to the putative genera <i>Acinetobacter</i>, <i>Pseudomonas</i>, <i>Sphingobium</i>, and <i>Rheinheimera</i>. The implications of this study suggest that enriching brackishwater with organic carbon sources at high C:N ratios may increase the likelihood of isolating and developing potential probionts for shrimp aquaculture.