Exploitation of agro-industrial wastes to produce low-cost microbial surfactants

Abstract

Biosurfactants have characteristic interfacial properties making them good emulsifiers, detergents, solubilizers, and foaming and wetting agents which could be exploited in industrial, agriculture, food, pharmaceutical, and personal-care sectors. Different microbial species have been reported to produce structurally diverse biosurfactants with different hydrophilic moieties and variations in length/composition of hydrophobic chains, thus providing options for wide range of applications. These surface-active molecules have functional properties similar to that of synthetic surfactants and retain their activities under extremes of temperature, pH, and salinity making them commercially promising biomolecules. Biosurfactants are envisaged as green alternatives to petrochemical-based toxic synthetic surfactants. The major deterrent to large-scale application of biosurfactants is their 10-30 % higher production cost than synthetic surfactants. The carbon and energy sources used in fermentation process generally account for 50 % of the overall biosurfactant production cost. Thus, efforts are being made to explore potential of renewable agricultural wastes and nutritionally rich low-value industrial by-products as substrates to bring down the overall production cost of biosurfactants. The abundant agro-industrial wastes, such as distillery wastes, plant oils, oil wastes, starchy substances, and whey, are the potential candidates as they are available throughout the year. The integrated approach of developing efficient microbial strains capable of growing on these alternative substrates and designing of low-cost nutritionally balanced optimized medium could significantly reduce the production cost of biosurfactants. The efforts to design efficient bioreactors for obtaining maximum biosurfactant yield using low downstream processing inputs could make the process economically viable. The application of biosurfactants for therapeutic and biomedical purposes demands high purity levels which increase the cost of downstream processing. However, application of biosurfactant preparations for field scale bioremediation does not need high level purity and thus would be in contention with chemical surfactants in future.