Characterization and application of a novel bioemulsifier in crude oil degradation by Acinetobacter beijerinckii ZRS

Abstract

Bioemulsifiers can be applicated in a variety of areas such as bioremediation and microbial-enhanced oil recovery. The present study was aimed at bioemulsifier production, optimization, stability studies, and applications of the bioemulsifier produced by one of these strains, Acinetobacter beijerinckii ZRS. When Acinetobacter beijerinckii ZRS is cultured with hexadecane as a carbon source, it produces a novel extracellular emulsifying agent that does not cause remarkable reductions in surface tension. In order to enhance bioemulsifier production, response surface methodology was applied to optimize the culture medium. The bioemulsifier was subjected to thin-layer chromatography, Fourier transform infrared spectroscopy (FTIR), gel filtration chromatography, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF), and nuclear magnetic resonance (NMR), which allowed for the identification of a novel polymeric bioemulsifier. The bioemulsifier retained its properties at a wide range of pH values, high temperatures and high salinities (up to 5% [w⁄v] Na(+) and 24% Ca(2+)). To deduce the role of this bioemulsifier in a coastal zone oil spill, the propagation of oil-degrading bacteria on oil-coated grains of gravel immersed in seawater was investigated in beach-simulating tanks. The bioemulsifier played a positive role in the degradation of these hydrocarbons and increasing the light crude oil degradation rate of the bacterial strain from 37.5 to 58.3% within 56 days. Therefore, this bioemulsifier shows strong potential to be used for bioremediation of oil pollution in marine environments.