Comparison of low and high molecular weight biosurfactants effects on the biodegradation efficiency of petroleum hydrocarbons

BACKGROUND AND OBJECTIVESLow molecular weight (LMW) surface-active agents reduce surface and interfacial tension, and high molecular weight (HMW) types effectively emulsify and mix hydrophobic compounds in the aqueous phase (Kumar et al., ۲۰۲۱). This study was aimed to compare the efficiency of bacteria producing LMW and HMW biosurfactants in degrading petroleum hydrocarbons.MATERIALS AND METHODSFor this purpose, ۱۸ bacterial isolates (isolated from different oil-contaminated areas) ability to produce LMW and HMW biosurfactants were evaluated based on the oil spreading and emulsion index (E۲۴) tests, respectively. The ability of isolates to degrade petroleum hydrocarbons was also determined in a crude oil enriched mineral salt medium (Aparna et al., ۲۰۱۲). Finally, the LMW and HMW surface-active biomolecules producing ability correlated with the hydrocarbons biodegradation efficiency.RESULTS AND DISCUSSIONThe results showed that seven isolates had a high ability to produce LMW biosurfactants and ۱۱ isolates showed higher ability to produce HMW biosurfactants. Among them, three isolates were able to simultaneously produce LMW and HMW biosurfactants. The highest rate of oil degradation (۹۲.۲%) was observed in Bacillus sp. İsolate, that had also the highest HMW biosurfactant production rate (E۲۴=۹۹%). The correlation test revealed a significant negative and positive correlation (r=-۰.۴۵* and r=۰.۵۸**)) between degradin efficiency and LMW and HMW biosurfactants producing, respectively. HMW surface-active agents emulsify stably the hydrophobic compunds in the aqueous phase, cause a better mixing of hydrocarbons in the liquid environment, lead to an increased bioavailabilty of hydrocarbons and their subsequent biodegradation (Sakhaei et al., ۲۰۲۲). While LMW biosurfactants can improve the hydrocarbons desorpsion from soil mineral or organic matrix by reducing surface and interfacial tension (Bagheri et al., ۲۰۲۲).CONCLUSIONThe results showed that bacteria producing HMW biosurfactants have a better ability to degrade hydrocarbons and can be considered as an effective indicator in the design and develop of biological products to clean up polluted water sources. However, investigation of enzymatic activity and other associated traits with hydrocarbon degradation is necessary for better understanding and accurate selection.