Surfactin for enhanced removal of aromatic hydrocarbons during biodegradation of crude oil

Abstract

Oil biodegradation studies using the powerful surfactant have mainly focused on saturated hydrocarbons or parent aromatic hydrocarbons, but not specifically on the position or degree of alkyl substitution of aromatic hydrocarbons. Removal of substituted aromatic hydrocarbons remains a controversial topic in biodegradation. In this study, the effect of surfactin addition on specific alkylated aromatic isomers and saturated hydrocarbons was observed in aerobic biodegradation experiments with four species of bacteria. The relative susceptibility of the individual alkylphenanthrene, alkyldibenzothiophene and methyltriaromatic steroid isomers to biodegradation was determined by their depletion rates. The results show that different bacteria induce removal of alkylated aromatic hydrocarbons and alteration of other petroleum hydrocarbons in various ways. Bacillus amyloliquefaciens strain BC is the best for biodegradation of general petroleum hydrocarbons, because it can convert n-alkanes, n-alkylcyclohexanes, isoprenoids, and aromatic hydrocarbons. Achromobacter strain J3 can degrade methylphenanthrenes, methyltriaromatic steroids, triaromatic steroids, and steranes better than other bacteria. Citrobacter sp strain J1 induces the highest degradation rate for dimethylphenanthrenes, trimethylphenanthrenes, and dimethyldibenzothiophenes, and Brucella melitensis strain J2 selectively degrades methyldibenzothiophenes. Surfactin addition increases the biodegradation rate of alkylaromatic hydrocarbons by 1.5–87.2%, and can significantly enhance the biodegradation of alkylphenanthrenes, alkyldibenzothiophenes and methyltriaromatic steroids. Alkyldibenzothiophenes can be used as markers for determining the levels of biodegradation of crude oils, and when used in conjunction with triaromatic steroids are a powerful indicator of the biodegradation of petroleum. The use of surfactin for enhancing the removal of aromatic hydrocarbons provides a wide range of applications in the environmental remediation and petroleum industry.