Surfactants double the biodegradation rate of persistent polycyclic aromatic hydrocarbons (PAHs) by a white-rot fungus Phanerochaete sordida

Polycyclic aromatic hydrocarbons (PAHs) are persistent in the environment and are toxic to humans and animals, rendering its remediation necessary but challenging. A white-rot fungus excellent in lignin degradation, Phanerochaete sordida YK-624, was chosen to improve biodegradation of high molecular weight thus persistent PAHs, assisted by surfactants. Efficacy to degrade three PAHs, phenanthrene, pyrene and benzo(a)pyrene, representing 3-, 4-, and 5-ring structure, was compared in liquid culture at low (5 mg L-1) and high (50 mg L-1) concentrations with or without fungi and/or surfactants. At the low concentration, phenanthrene and pyrene were completely degraded by P. sordida YK-624 after 8 and 16 day incubation, while 88.9% benzo(a)pyrene degradation was observed by 24 days. Degradation of phenanthrene, pyrene and benzo(a)pyrene at the high concentration reached 89.2%, 61.9% and 28.6%, respectively, after 32 day incubation. In addition, the t(1/2) of phenanthrene were 1.17 or 11.55 days, while the t(1/2) of pyrene and benzo(a)pyrene were 1.93 or 17.33 days and 7.70 or 69.30 days, for low or high concentrations, respectively. The highest mycelial biomass at 46.1 mg was observed in incubation of 5 mg L-1 benzo(a)pyrene, exceeding the biomass in the control by 10 mg, suggesting that P. sordida YK-624 might utilize PAHs as a substrate for growth. With increasing concentration of cytochrome P450s inhibitor piperonyl butoxide (PB), the degradation of PAHs decreased, demonstrating the involvement of cytochrome P450s. For instance, the removals of phenanthrene, pyrene and benzo(a)pyrene at the low concentration were 85.7%, 36.3% and 49.0% in the presence of 500 mg L-1 PB at 24 days, compared with the controls of 100%, 100%, and 88.9%, respectively. Furthermore, three nonionic surfactants enhanced benzo(a)pyrene degradation. The 32 day degradation of benzo(a)pyrene was increased to 62.4%, 41.9% and 53.3% when 1 g L-1 Brij 30, 1 g L-1 Triton X-100, and 2 g L-1 Tween 80 were added. Benzo(a)pyrene degradation was increased approximately twofold by the addition of 1 g L-1 Brij 30. Thus, P. sordida YK-624 holds the potential for bioremediation of persistent PAHs, especially with the addition of nonionic surfactants.

Automated summary

In this study, a white-rot fungus Phanerochaete sordida YK-624 was used to enhance the biodegradation of high molecular weight and persistent PAHs. The addition of nonionic surfactants significantly improved the degradation of benzo(a)pyrene. This finding suggests that P. sordida YK-624 has the potential for bioremediation of persistent PAHs.