Isolation, Fermentation Optimization and Performance Studies of a Novel Biosurfactant Producing Strain Bacillus amyloliquefaciens

Petroleum hydrocarbon is the main source of energy in the world, as well as the main pollutant of soil and water. Accidental spills, uncontrolled landfills or improper storage and leaking underground storage tanks can all lead to contamination1. Compared with physicochemical methods, bioremediation has gained increasing interest in dealing with petroleum hydrocarbons, as it is environmentally friendly, cost-effective, efficient, while the end products of this process are mostly not harmful to environment2. Bioremediation refers to the complete elimination or conversion of toxic recalcitrant compounds into non-toxic forms by a bacterium or a microbial consortium3. However, microbial biodegradation is usually impeded by the limited low water solubility of petroleum hydrocarbon and limited capacity of bacteria to access and degrade the substrate4. The bioavailability of hydrocarbons can be enhanced by adding biosurfactant to the contaminated ecosystems to facilitate the uptake of bacteria5. Also, the biosurfactant can help the oil recovery process during water flooding in the oil field. Biosurfactants are a diverse group of surface-active chemical compounds with unique biochemical properties and are produced by a wide variety of microorganisms6. Based on the chemical composition and microbial origin, biosurfactants are classified as glycolipids, lipopeptides, fatty acids, polymeric type and particulate biosurfactants7. The most commonly isolated biosurfactants are glycolipids and lipopeptides, such as rhamnolipids8, sophorolipids9, surfactin and iturin10. Lipopeptides are effective biosurfactants which are usually produced by Bacillus strains. Biosurfactants are amphiphilic compounds containing both hydrophilic and hydrophobic moieties in their structure and can reduce both surface and intersurface tensions which make them useful in emulsification processes6. They can form micelles to facilitate the process of emulsification of hydrocarbons in aqueous phase and enhance their availability for microbial uptake and degradation11, the enhancement of biosurfactants is probably due to the increase in cell surface hydrophobicity that allows direct contact between the cell and the hydrocarbons12. Hence, they have potential for application in the degradation of hydrocarbon pollutants. Compared with chemically synthesized surfactants, biosurfactants are of better environmental compatibility, higher foaming activity, lower toxicity, higher selectivity, biodegradability and specific activity in extreme conditions (temperatures, pH, and salinities)13,14. These attributes make biosurfactants promising alternatives to chemical surfactants Isolation, Fermentation Optimization and Performance Studies of a Novel Biosurfactant Producing Strain Bacillus amyloliquefaciens