EFFECTS OF OPTIMIZATION OF NUTRITIONAL REQUIREMENTS AND INFLUENCE OF ENVIRONMENTAL PARAMETERS ON BIOSURFACTANTS DERIVED FROM MARINE BACTERIA

In the present study, biosurfactant-producing microorganisms such as KM1 (Bacillus licheniformis – Kasemedu 1), KM2 (Bacillus subtilis – Kasemedu 2), ER1 (Pseudomonas aeruginosa – Ennore site 1), ER1B (Pseudomonas mendocina – Ennore site 1) and ER9 (Streptococcus lactis – Ennore site 2) were subjected to optimization studies. The optimization study was carried out using various carbon, nitrogen sources, pH, temperature, hydrocarbons, and trace elements. The effect of dry cell biomass, biosurfactant production, emulsification activity, and surface tension were studied. Among the five isolates, KM2 and ER1 grew well in sucrose at 1% concentration. Production and activity of the biosurfactant were found to a maximum at pH 7.0, and an additional increase in pH during bacterial growth does not affect the surfactant activity till pH 8.5±0.2; however, a decrease in pH showed a significant effect on the surfactant activity. The optimum temperature was identified as 37°C for all the isolates and below and above this temperature markedly affects the biosurfactant production and activity. Observations on reduction in surfactant activity with an increase in agitation above 200 rpm, were reasoned to the reduced uptake of nutrients during agitation. After 36 hours of incubation, the biosurfactant activity of all five isolates was highly pronounced and reduces the surface tension of water to lower than 33 mN/m. The isolate KM2 reduces the surface tension still lower to 23 mN/m.