Characterization of Antimicrobial Bioactive Compounds and Antibacterial Potential of Ulva fasciata Delile Isolated from West Coast of Kanyakumari, India

Six seaweed species, Bryopsis plumose (Hudson)C.Agardh, Caulerpa racemose (Forskall) J.Agardh, Ulva fasciata Delile, Sargassum longifolium (Turner) C. Agardh, Gracilaria corticate (J.Agardh) J. Agardh and Sargassum wightii Greville ex J. Agardh were collected at Kadiyapattinum Coast of Kanyakumari District. They were shade dried, powdered and extracted with 100% methanol and screened the phytochemicals by standard analytical protocols. Among the seaweeds, U. fasciata showed the presence of alkaloids, glycosides, phenols, steroids, tannins and terpenoids also found in rich of total protein and carbohydrate. Based on the initial screening U. fasciata was selected for further antimicrobial study and serially extracted with methanol, chloroform, ethyl acetate, acetone and hexane and screened antibacterial and antifungal activity. Among the selected solvents, methanol extract of U. fasciata showed high activity against Staphylococcus aureus, Bacillus sp., Klebsiella pneumonia and Aeromonas hydrophila. The methanol extracts effectively controlled the bacterial pathogens at the zone of inhibition of 8.11, 11.33, 13.87 and 17.76 mm against Bacillus sp., S. aureus, K. pneumonia and A. hydrophila respectively. Antifungal screening result revealed that, very least activities, less than 3mm were observed against the fungal pathogens, Candida albicans, Rhizopus oryzae and Aspergillus flavus. Fourier-Transform Infrared Spectroscopy revealed the presence of alcohol, alkenes, aromatic, amine, phenyl, ether, methylene, primary amines, and aliphatic chloro compound in the methanolic extract of U. fasciata. In order to characterize the antimicrobial protein, crude extract was purified through sephadex G-75 gel filtration chromatography and characterized the antimicrobial protein found to be 13 kDa. Further the methanolic extract of U. fasciata at different concentrations (100,200 & 400 mg/Kg) was incorporated the diets were fed to the ornamental gold fish Carassius auratus for 30 days and challenged with virulent A. hydrophila and studied the survival, specific bacterial load reduction. The highest concentrations of U. fasciata diets fed fishes had significantly (P<0.05) improved survival and reduced Aeromonas count in the blood. This study concluded that, U. fasciata extract improve survival and also helped to reduce the Aeromonas load at in vivo level which was useful to develop antibacterial diets in the fresh water aquaculture industry.