APPLICATION OF BIOSURFACTANT IN OIL SPILL MANAGEMENT

Abstract

ABSTRACT Surfactants are surface active agents which reduce surface tension and interfacial tension between two immiscible phases and help in emulsification. Toxicity, nonbiodegradability, and limited structural types of chemical surfactants have initiated the need for effective substitutes. Biosurfactants, which are synthesized by specific microbial cultures, have surface active properties comparable to chemical surfactants. They are compounds that can help in oil spill cleanup operations without presenting the problems posed by chemical surfactants. Two bacterial cultures were isolated from oil-contaminated soil and were used for biosurfactant production. The biosurfactants produced by the Bacillus licheniformis, BS1, and Pseudomonas aeruginosa, BS2, in mineral media containing glucose as the carbon source belong to the class of lipoprotein and glycolipid, respectively. They were found to reduce the surface and interfacial tension of water and water-hexadecane systems from 72 dynes/cm and 40 dynes/cm to 28 to 30 dynes/cm and 1 to 3 dynes/cm, respectively. These results were comparable with chemical surfactants with respect to surface tension reduction (Slic Gone 34 dynes/cm and Castrol 30 dynes/cm). The low interfacial tension allows the formation of stable emulsion. The two cultures were grown on different substrates, namely, glucose, mannitol, glycerol, hexadecane, oily sludge, and crude oil. Emulsion formation of hexadecane in water was tested with the cell-free broth containing biosurfactant from the respective substrate broths. Emulsions of 56 percent stability to 100 percent stability were obtained from these biosurfactant-containing broths. Both biosurfactants were able to emulsify crude oil. A surfactant's ability to form a stable emulsion is the first step in oil spill cleanup. The emulsified oil can then be acted upon very easily by the microorganisms under study. Therefore, the biosurfactants produced by the microorganisms under study offer a good potential for use in oil spill cleanup.