Evaluation of marine macro alga, Ulva fasciata against bio-luminescent causing Vibrio harveyi during Penaeus monodon larviculture

Abstract

Vibrio harveyi is one of the major disease causing bacterium in shrimp larviculture and grow-out practices. V. harveyi produces many virulence cum pathogenic factors. Application of antibiotics against luminescence causes development of antibiotic resistance among V. harveyi. Therefore, it is obligatory to develop bio-inhibitory agents as substitute in lieu of antibiotics. Under this study, Ulva fasciata was collected and extracted for crude compounds, 300 µg extract showed 12.3 mm of bioinhibition against V. harveyi through “agar well diffusion assay”. Further, U. fasciata extract at 300 µg/ml was treated against V. harveyi in LB broth and showed reductions on phospholipase and proteolysis. Production of bio-luminescence was reduced to 7.3, 7.7, 13.0, 17.0 counts per second (CPS) and growth also reduced to 24.91%. Further, U. fasciata extract at 200 g/ml was tested against V. harveyi during Penaeus monodon larviculture and showed 32.40% reduction in the cumulative percentage mortality on postlarvae due to V. harveyi. Chemical constituents of U. fasciata was characterized by FTIR and GCMS. GC-MS analysis, reported to contain organic compounds such as Bis(2-ethylhexyl) phthalate was highest (88.42%), followed by 1,2- benzenedicarboxylic acid- butyl (2.47%). Therefore, it was concluded that U. fasciata may be a better bio-inhibitory agent against V. harveyi in shrimp larviculture.