Biosurfactant Production by Streptomyces sp. CGS B11 Using Molasses and Spent Yeast Medium

Biosurfactants are considered a good alternative to highly-polluting petroleum-based surfactants that are toxic and non-biodegradable in nature. However, the high production cost of biosurfactants limits its potential for commercialization. The use of a highly efficient biosurfactant-producing actinomycetes isolate, combined with the utilization of low-cost substrates such as agro- industrial wastes, may aid in lowering the overall production cost. In this study, twenty-eight (28) actinomycetes isolated from distillery wastes and soil samples were screened for the production of extracellular biosurfactants. Based on the preliminary screening experiment, isolate CGS B11 – molecularly identified as Streptomyces angustmyceticus – produced the biosurfactant with the highest emulsification activity (E24). Subsequently, the best alternative carbon and nitrogen sources, salt supplement, and pH level were determined using one-factor-at-a-time (OFAT) experiments. The highest measured biosurfactant activity was observed in the medium containing molasses, spent yeast autolysate, and NaCl, and a pH level ranging from 6.0–7.0. Biosurfactant production was observed to be growth associated with maximum emulsification activity achieved after 4 d of fermentation (late log phase). FTIR (Fourier transform infrared) spectra and biochemical composition analyses of the S. angustmyceticus CGS B11 biosurfactant suggest that it belongs to the lipopeptide type of biosurfactants. S. angustmyceticus CGS B11 biosurfactant also showed resistance and high stability on a wide range of temperature, pH, and salinity, and the ability to form stable and dense emulsions with various oils tested. It has great potential for various applications such as in the food and pharmaceutical industries, and in oil recovery and bioremediation. The results of this study will hopefully serve as a basis for large-scale production of biosurfactants utilizing agro-industrial wastes in the country.