Abstract
Marine microalgae may produce antibacterial substances. At the exponential phase of growth, four species of marine microalgae were examined for their potential to create secondary metabolites that limit the growth of Vibrio harveyi: Nannochloropsis oceanica, Chaetoceros gracilis, Isochrysis sp., and Thalassiosira weissflogii. V. harveyi is a pathogenic bacteria that can cause severe mortality and loss in aquaculture. Disc diffusion assay and co-culture assay were used to determine antibacterial activity. On TSA % NaCl media, the disc impregnated with microalgae and extracted with ethanol, methanol, saline water, and dimethyl sulfoxide (DMSO) was tested against V. harveyi at concentrations of 1.0 × 105, 106 and 107 CFU mL−1. The disc diffusion assay revealed that N. oceanica extracted with ethanol had the largest inhibitory zone against V. harveyi. Meanwhile, only N. oceanica, Isochrysis sp., and T. weissflogii reduced the growth of V. harveyi (105 CFU mL−1) in the co-culture assay (p < 0.05). The current findings reveal that the hydrophilic chemicals in microalgae extract have antibiotic activity against the highly virulent V. harveyi, which causes vibriosis, a serious disease in farmed fish and aquaculture cultivation around the world.
Highlights
In recent years, the aquaculture business has grown quickly and is predicted to supply approximately 62% of fish for human demand and consumption by 2030 [1,2]
Vibriosis is associated with infections in fish, such as skin necrosis, ulceration, and scale drops on the abdomen caused by a variety of Vibrio spp., including Vibrio harveyi, V. vulnificus, V. parahaemolyticus, V. alginolyticus, V. penaeicida, and V. splendidus [5]
Previous studies have suggested that fatty acids [23], terpenoids, carbohydrates [24], peptides, polysaccharides, and alkaloids are responsible for antibacterial activity in microalgae [25]
Summary
The aquaculture business has grown quickly and is predicted to supply approximately 62% of fish for human demand and consumption by 2030 [1,2]. Vibriosis is one of the most prevalent bacterial diseases and is claimed to have damaged farmed marine fish in Malaysia, resulting in a USD 7.4 million loss in 1990 [3] and severe economic loss to Asian seabass farmers in 2017 [4]. Antibiotics and chemicals are frequently used by farmers to combat harmful organisms. They have been used sparingly since they are expensive, non-biodegradable, highly biomagnified, and antibiotic resistance has grown [7]. Antibiotic overuse can result in various environmental problems, including contamination of the culture environment, organism harm, and the development of bacterial resistance that can extend to the food chain [8]. Numerous techniques for controlling pathogenic vibriosis have been proposed, including phage therapy, short-chain fatty acid inhibition of bacterial growth, quorum-sensing disruption, probiotics, immunostimulants, vaccinations, and green water [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
