Contrasting characteristics of anthracene and pyrene degradation by wood rot fungus Pycnoporus sanguineus H1

Abstract

This investigation evaluates the contrasting metabolic characteristics of anthracene and pyrene by wood rot fungus Pycnoporus sanguineus H1. Under in vivo conditions, P. sanguineus H1 degraded 67.5% of the anthracene and showed maximal laccase activity of 1568.2 U L−1. When piperonyl butoxide (PB) was added to the liquid cultures, the anthracene degradation rate increased to 73.1% and maximal laccase activity increased to 2034.3 U L−1. For pyrene, the degradation rate was 31.1%; however, after PB addition, the value decreased to 5.3% while maximal laccase activity increased to 1625.3 U L−1 from 1469.1 U L−1. Under in vitro conditions, the extracellular liquid culture (10 kDa membrane, ultra-filtered) transformed 59.9% of the anthracene, while addition of 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) enhanced the anthracene transformation rate up to 92.0%. The extracellular liquid did not convert the pyrene, however, suggesting that anthracene is modified extracellularly, (likely via laccase) while pyrene is not. Whole mycelium, as well as homogenized mycelium and microsomal proteins, transformed both anthracene and pyrene; conversion was inhibited to some extent by the PB, implying that cytochrome P450 participates in intracellular PAHs transformation. Additional evidence that ABTS enhances anthracene transformation by homogenized mycelium suggests that mycelium-associated laccase cooperates in the intracellular degradation of anthracene. These results altogether elucidate the metabolism of PAHs by P. sanguineus via extracellular laccase, intracellular cytochrome P450, and mycelium-associated laccase.