Biodegradation of polycyclic aromatic hydrocarbons by Acremonium sp. activity

Chihuahua State is the largest apple producer in Mexico. To prevent apples from freezing during the winter, petroleum-based fuels are used to heat the orchards. In this research work, a microorganism isolated from inside of a fuel plastic container was identified through morphological analysis as the fungus Acremonium sp. By cultivating the fungus in potato dextrose agar medium (PDA), we were able to study the biodegradation rates of three polycyclic aromatic hydrocarbons (PAHs). The isolated microorganism was incubated at 28 ºC in M9 mineral liquid medium using phenanthrene, anthracene, and pyrene as the only carbon source at a concentration of 50 µg/mL. Degradation of PAHs was monitored using an environmentally friendly reverse phase ultra-high-performance liquid chromatography (UHPLC) system, with a C18 column, 30% water acidified at 0.1% with trifluoroacetic acid, and 70% acetonitrile as the mobile phase, 40 ºC column temperature, and UV detection at 254 nm. After 30 days of biodegradation (optimal time), the final mean concentration for individual degradation experiments were 2.51 µg/mL phenanthrene, 3.02 µg/mL anthracene and 5.53 µg/mL pyrene. Those final concentrations indicate degradation percentile of 95%, 94%, and 89%, respectively. Biodegradation experiments combining all three PAHs showed similarly high degradation percentiles of 93%, 94%, and 85% for phenanthrene, anthracene, and pyrene, respectively. The dry weight average at day 30 in the individual and combined degradation experiments was 2.34 mg/mg PAHs degraded.