Effective phenanthrene and pyrene biodegradation using Enterobacter sp. MM087 (KT933254) isolated from used engine oil contaminated soil

Abstract

Phenanthrene and pyrene are low and high molecular weights polycyclic aromatic hydrocarbons (PAHs) being classified as priority organic pollutants in the environment. This study was aimed to optimizing PAHs biodegradation conditions and then identifying intermediate metabolites using effective Enterobacter sp. MM087 (KT933254). Biodegradation quantitative experiments were carried out using colorimetric assay and the intermediate metabolites were identified based on gas chromatography mass spectrophotometer (GC–MS). Enterobacter sp. MM087 initially degraded 80.2% phenanthrene (500mg/L) and 59.7% pyrene (250mg/L) within 24h. Further enhancement of the culture conditions involving agitation, temperature, pH, inoculums volume and salinity was carried out using response surface methodology (RSM) based on central composite design (CCD). The CCD optimizations allowed the interactions among the culture conditions which eventually resulted in 100% degradation in each of the phenanthrene and pyrene thereby released non-hazardous metabolites. Correlation between the predicted and actual results further validated the CCD optimization. The phenanthrene metabolites identified were 3,4-dihydroxyphenathrene, phthalate, pyruvic acid and acetic acid. Pyrene metabolites identified involved pyrene cis-4,5-dihydrodiol, 3,4-dihydroxyphenathrene, phthalate, pyruvic acid, acetic acid and formic acid. The biodegradation experiments were finally validated using numerical optimizations. Enterobacter sp. MM087 was found to rapidly degrade 500mg/L phenanthrene and 250mg/L pyrene within 24h which makes it a very efficient and rapid PAHs degrader.