Effects of surfactant and temperature on biotransformation kinetics of anthracene and pyrene

The biotransformation and mineralization of a mixture of two polycyclic aromatic hydrocarbons (PAHs), anthracene and pyrene, which are known contaminants of soil and groundwater, by an enrichment culture in the presence or absence of 100 mg l−1 Tergitol NP-10, a non-ionic surfactant, and at temperatures of 10 °C and 25 °C were investigated. The overall biotransformation of 2 mg l−1 total PAHs with free cell suspensions in batch culture was greater than 97.2% at both examined temperatures. At 25 °C, the overall mineralization of anthracene was 48.8% and that of pyrene was 66.1%. However, the decrease of temperature to 10 °C had a negative effect on the mineralization of PAHs and reduced it to 18.5% and 61.5% for anthracene and pyrene, respectively. Using a higher PAHs concentration of 20 mg l−1 at 25 °C, the overall biotransformation of anthracene was 80.7% and that of pyrene was 100%, where only 17.3% anthracene and 7.6% pyrene were mineralized to carbon dioxide and water. The addition of surfactant at 25 °C increased the overall mineralization of anthracene and pyrene to 33.0% and 27.6%, respectively. However, the addition of surfactant at 10 °C had a negative impact on the overall biotransformation of anthracene and pyrene, reducing them to 20.6% and 14.0%, respectively. These results have significant implications in the bioremediation of PAHs-contaminated sites.