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.

Production, characterization, and applications of bioemulsifiers (BE) and biosurfactants (BS) produced by Acinetobacter spp.: A review

“…Maximum emulsification activity noted for Acinetobacter junii SC14 is 1759.8 EU ml −1 followed by A. calcoaceticus BD4, i.e., 593 EU ml −1 . Emulsification activity in % is also recorded for some BE and it was found that A. calcoaceticus RAG‐l showed maximum activity, i.e., 80.75% followed by two other strains such as A. calcoaceticus MM5 and A. beijerinckii ZRS, i.e., 80% . Most of the BE showed applications in degradation of variety of oils and aromatic as well as aliphatic hydrocarbons.…”

“…All carbon sources used by different strains of Acinetobacter showed influence on bioemulsifier production and helped in increasing yield of the same. Among all BE, maximum yield recorded is 5.16 g L −1 for lipoprotein bioemulsifier produced by A. beijerinckii ZRS, followed by lipoglycan nature of bioemulsifier (5.05 g L −1 ) produced by Acinetobacter baumanii AC5 . Hayder, reported use of 1% olive oil and sesame oil (edible oil) in production media increased yield of bioemulsifier to the maximum extent .…”

“…Zhao et al reported hexadecane as sole source of carbon used for its production. Like carbon source, nitrogen source is also another important parameter for maximum bioemulsifier production . The nitrogen source was reported to influence the production of lipoglycan bioemulsifier.…”

“…It is also important to note that carbon and nitrogen sources not only increase production yield but also influence emulsification activity of BE . Effect of pH on the stability and production of BE was studied for some of the BE.…”

“…The biosurfactant obtained from A. beijerinckii ZRS was responsible for increasing the rate of crude oil degradation from 37.5 to 58.3% in span of 56 days. As the biosurfactant was able to retain its properties even at wide range of high salinities, i.e., up to 5% (w/v) Na + and 24% Ca 2+ , it was concluded that this biosurfactant has ability to play a critical role in bioremediation of marine environments for example coastal areas polluted by oil spillage .…”