Optimization of Laccase-mediated Benzo[a]pyrene Oxidation and the Bioremedial Application in Aged Polycyclic Aromatic Hydrocarbons-contaminated Soil

Abstract

Laccase is a polyphenol oxidase with the ability to oxidize a broad range of persistent organic pollutants, including benzo[a]pyrene, the most carcinogenic, mutagenic and teratogenic polycyclic aromatic hydrocarbons (PAHs). In this study, the reaction conditions for benzo [a]pyrene oxidation by laccase from Trametes versicolor were optimized in a liquid medium by a series of single factor experiments. The maximal benzo[a]pyrene oxidation rate was observed at 40• C, pH 4, 10% of acetonitrile and an incubation time of more than 24 hr, and the benzo[a]pyrene oxidation was enhanced significantly by the addition of a mediator, 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonicacid) (ABTS). Laccase was also applied to aged PAHs polluted soil to examine the efficiency of enzymatic bioremediation. The results showed that the enzyme was still effective in the degradation of anthracene, benzo[a]pyrene and benzo [a]anthracene in soil. Moreover, the degradation rate of most PAHs increased by the addition of ABTS. Our results indicated that the bioremediation of PAHs contaminated soil using laccase is feasible but a suboptimal pH might be a limiting factor in the enzymatic treatment of soil.

Laccase oxidation and removal of toxicants released during combustion processes

“…This may be influenced by a number of factors including the redox potential of these substrates, which is higher than that of laccase (Li et al, 2010) as well as the reaction conditions. For example, laccase from Trametes versicolor with a redox potential similar to that of T. villosa (Reinhammar, 1972;Collins and Kotterman, 1996;Li et al, 2010) used here was able to effectively oxidize benzo[a]pyrene and benz[a]anthracene although the same authors were also surprised to note that pyrene with lower redox potential was not oxidized. In contrast, Majcherczyk et al, 1998 reported oxidation of pyrene using the same T. versicolor laccase.…”

Enzymatic Catalysis of Hydrocarbons Oxidation “in vitro” (Review)

“…Moreover, the degradation rate of most PAHs increased by the addition of ABTS. These results indicated that the bioremediation of PAHs contaminated soil using laccase is feasible but suboptimal pH might be a limiting factor in the enzymatic treatment of soil [36].…”

“…In the study [36] the reaction conditions for benzo[α]pyrene oxidation by laccase from Trametes versicolor were optimized in a liquid medium by a series of single-factor experiments. The maximal benzo[α]pyrene oxidation rate was observed at 313 K, pH 4, 10% of acetonitrile and an incubation time of more than 24 hr, and the benzo[α]pyrene oxidation was enhanced significantly by the addition of a mediator, 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonicacid) (ABTS).…”

Microbial Ecology of Hydrocarbon Degradation in the Soil: A Review

“…For example, naphthalene is the simplest with two rings and is the most soluble of the PAHs (Mrozik et al, 2003). On the other hand, benzo[a]pyrene, a typical high molecular weight PAHs with five rings, is one of the most recalcitrant and toxic PAHs (Li et al, 2010). The chemical properties of individual PAHs are reliant in part upon molecular size (that is their no.…”