Screening of microalgae with the potential as anti quorum sensing and anti-vibrio agent in shrimp culture.

Vibriosis is a major bacterial disease that causes significant mortality in farmed shrimp worldwide. Numerous studies have explored strategies to prevent mass mortalities associated with vibriosis outbreaks. This study aimed to identify microalgal species with immunostimulant and anti-Vibrio properties for shrimp culture. Microalgal screening began with centrifugal supernatant extraction, followed by metabolite extraction using ethyl acetate. The metabolites were subjected to an anti-quorum sensing (QS) bioassay via the disc diffusion method, using Chromobacterium violaceum as an indicator strain on LB agar. Clear inhibition zones around the discs indicated anti-QS activity. Anti-Vibrio activity was assessed using the microalgae metabolites, with Vibrio harveyi as the target strain on TSA medium. Microalgal supernatant extracts were further tested for anti-Vibrio activity under both in vitro and in vivo conditions. The experiment followed a completely randomized design with five treatments and three replicates. Based on the bioassays, Melosira sp., Porphyridium sp., and Phaeodactylum tricornutum demonstrated the ability to inhibit Vibrio growth. Challenge test results indicated that extracts of P. tricornutum and Porphyridium sp. have strong potential to suppress pathogenic Vibrio in shrimp aquaculture.