R. Gandhimathi

Optimization and production of a biosurfactant from the sponge-associated marine fungus Aspergillus ustus MSF3

Marine endosymbiotic fungi Aspergillus ustus (MSF3) which produce high yield of biosurfactant was isolated from the marine sponge Fasciospongia cavernosa collected from the peninsular coast of India. Maximum production of biosurfactant was obtained in Sabouraud dextrose broth. The optimized bioprocess conditions for the maximum production was pH 7.0, temperature 20 degrees C, salt concentration 3%, glucose and yeast extract as carbon source and nitrogen sources respectively. The response surface methodology based analysis of carbon and nitrogen ratio revealed that the carbon source can increase the biosurfactant yield. The biosurfactant produced by MSF3 was partially characterized as glycolipoprotein based on the estimation of macromolecules and TLC analysis. The partially purified biosurfactant showed broad spectrum of antimicrobial activity. The strain MSF3 can be used for the microbially enhanced oil recovery process.

Production and characterization of lipopeptide biosurfactant by a sponge-associated marine actinomycetes Nocardiopsis alba MSA10.

A sponge-associated marine actinomycetes Nocardiopsis alba MSA10 was screened and evaluated for the production of biosurfactant. Biosurfactant production was confirmed by conventional screening methods including hemolytic activity, drop collapsing test, oil displacement method, lipase production and emulsification index. The active compound was extracted with three solvents including ethyl acetate, diethyl ether and dichloromethane. The diethyl ether extract was fractionated by TLC and semi-preparative HPLC to isolate the pure compound. In TLC, a single discrete spot was obtained with the Rf 0.60 and it was extrapolated as valine. Based on the chemical characterization, the active compound was partially confirmed as lipopeptide. The optimum production was attained at pH 7, temperature 30°C, and 1% salinity with glucose and peptone supplementation as carbon and nitrogen sources, respectively. Considering the biosurfactant production potential of N. alba, the strain could be developed for large-scale production of lipopeptide biosurfactant.

Antimicrobial potential and seasonality of red algae collected from the southwest coast of India tested against shrimp, human and phytopathogens

Fifteen seaweeds belong to 13 families and 6 orders of the rhodophyta were sampled for one year from April 2007 to March 2008 along the southwest coast of India (Indian Ocean). The species were examined forin vitro antimicrobial activity against six pathogenicVibrio strains isolated from moribund tiger shrimp (Penaeus monodon), six type cultures (Microbial Type Culture Collection, MTCC) of prominent shrimpVibrio pathogens, 10 multidrug resistant clinical pathogens, four species ofCandida obtained from pulmonary TB patients and four species of plant pathogenic fungi to evaluate their potency to be used as natural antibiotics in pharmaceutical and agriculture field. Bioactivity was analyzed from crude extract of fresh and dried samples prepared from different polar and nonpolar solvents. Of these, four species of red algae (Asparagopsis taxiformis, Laurencia ceylanica, Laurencia brandenii, Hypnea valentiae) were found to be highly active. Broadest and highest activity was observed in the crude extract ofA. Taxiformis. Among the pathogens tested, shrimp pathogenicVibrios were the most susceptible organisms while phytopathogens were found to be little resistant. In the present study, methanol was found to be the best solvent for extracting antimicrobial metabolites from dried samples rather than fresh. Seasonal variation in the antimicrobial activity was observed with higher level of activity recorded fromA. Taxiformis between December and January. The active principle ofA. Taxiformis was purified in column chromatography, TLC and reverse phase HPLC. The individual HPLC peaks were subsequently tested against a panel of pathogenic microorganisms and the active constituent was identified by GC-MS. The antimicrobial profile ofA. Taxiformis suggested that lipophilic compound which was primarily composed of pyrrole-2-carboxylic acid, pentadecanoic acid and octadecanoic acid might have functional role in the chemical defence against microbial invasion and these compounds could be utilized for the development of medically potential products.