Growth management of white-rot fungus Phlebia brevispora improved degradation of high-molecular-weight polycyclic aromatic hydrocarbons

The effect of co-culturing white-rot fungus Phlebia brevispora with growth-promoting bacterial strains Enterobacter sp. TN3W-14 and Pseudomonas sp. TN3W-8 on the degradation of polycyclic aromatic hydrocarbons (PAHs) was evaluated in liquid culture. In axenic cultures, P. brevispora strains TN3F and TMIC33929 showed high degradation of phenanthrene (> 98%) within 15 days, and degraded 65% and 63% of pyrene, and 12% and 8% of benzo(a)pyrene, respectively. This low level of degradation ability toward benzo(a)pyrene was improved significantly by co-culturing the fungi with a mixture of bacterial strains TN3W-8 and TN3W-14 (mixed bacterial co-culture; MBC). Within 15 days, P. brevispora TN3F with MBC achieved about 86% pyrene and 53% benzo(a)pyrene degradation; P. brevispora TMIC33929 with MBC showed 92% pyrene and 72% benzo(a)pyrene degradation. The MBC alone degraded little PAH, as its growth was inhibited by PAH; however, its co-culture with P. brevispora improved mycelial growth of the fungus, which led to improved degradation of the PAHs. A possible dihydrodiol metabolite of pyrene from fungal cultures suggests that hydroxylation was the first step in the degradation of pyrene by P. brevispora.