Studies on synthesis of biosurfactants and their applications

Abstract

Surfactants are surface active compounds capable of reducing surface and interfacial tension at the interfaces between liquids, solids and gases, thereby allowing them to mix or disperse readily as emulsions in water or other liquids. The enormous market demand for surfactants is currently met by numerous synthetic, mainly petroleum based, chemical surfactants, which are toxic to environment and not easily biodegradable. In the present research work, studies were carried out on synthesis and culture media optimization of three industrially important biosurfactants sophorolipids, surfactin and rhamnolipids. After ascertaining the optimum process conditions, two unconventional substrates, waste frying sunflower oil and waste frying rice bran oil were employed as carbon substrates, and the yield of biosurfactants produced were reported. The objective of utilizing the waste frying oils is not only to decrease the product cost but to find an avenue to dispose eco hazardous waste. Glucose was found to be the best carbon source for the synthesis of surfactin from Bacillus subtilis MTCC 2423 at a concentration level of 3 g/l, which produced 1.285 g/l of surfactin. Glucose was found to be the best carbons substrate for Pseudomonas aeruginosa MTCC 2297. Optimum levels of glucose, sodium nitrate, temperature and pH were found to be 3.48 g/l, 0.39 g/l, 34.07and#8304;C, 7.4 respectively, by response surface methodology. Sophorolipids produced with glucose substrate (SL-G) has shown very good inhibitory action on Staphylococcus aureus and Micrococcus luteus at low concentrations. Average particle size produced as per the EDX analysis was found to be 20.81 nm. XRD analysis was used to study the nature of the silver nanoparticle. From the above studies it can be concluded that, waste frying oils can be profitably used to synthesize biosurfactants, which are required in bulk quantities for various medicinal, industrial and environmental applications.