Degradation of PAHs by ligninolytic enzymes of Irpex lacteus

Abstract

The ligninolytic fungus Irpex lacteus was shown as an efficient degrader of oligocyclic aromatic hydrocarbons (PAHs; 'polycyclic aromatic hydrocarbons') possessing 3-6 aromatic rings in complex liquid media. The strain produced mainly Mn-dependent peroxidase in media without pollutants. Activity of ligninolytic enzymes was higher in a N-limited medium. However, after contamination with PAHs (especially pyrene) the values increased and significant activity of Mn-independent peroxidase appeared in the complex medium. Other factors (such as the increase in nitrogen concentration or the presence of solvent(s) for dissolution of PAHs) had no effect. Cytochrome P-450 was detected in the microsomal fraction of biomass grown in the complex medium. The rate of PAH degradation was also affected by the presence of various combinations of PAHs. However, independently of the enzyme activities, anthracene was shown to have a positive influence on degradation of pyrene and fluoranthene.

Characterization of a Novel Dye-Decolorizing Peroxidase (DyP)-Type Enzyme from Irpex lacteus and Its Application in Enzymatic Hydrolysis of Wheat Straw

“…I. lacteus reduced peroxidase production until the third week of incubation, when MnP production increased again, together with a peak of DyP, which was able to oxidize high-redox-potential substrates such as anthraquinones. DyP appeared when the carbon/nitrogen ratio in the cultures was very low, which is in accordance with the production profile reported by Cajthaml et al (8) in I. lacteus liquid cultures spiked with polycyclic aromatic hydrocarbons (PAHs). Laccase was not detected, which suggests that both DyP and MnP are the main oxidative enzymes secreted by I. lacteus under these culture conditions.…”

Influence of PAHs on ligninolytic enzymes of the fungus Pleurotus ostreatus D1

“…Such compounds were also showed to be products of PAH degradation [35]. The study of influence of some products from PAH degradation [44][45][46] on laccase production revealed that the presence of phthalic acid or 2,2'-diphenic acid did not result in a noticeable increase in laccase production by P. ostreatus D1 and that catechol inhibited it completely.…”

“…However the presence of chrysene, benzo[a]anthracene, benzo[a]pyrene or benzo[g,h,i]perylene did not affect the ligninolytic enzyme activity. Authors attributed this to a lower solubility that significantly influences the availability of the compounds for the organisms [35].…”

“…Generally, the greatest effects were observed after 3 days of cultivation for laccase and after 10 days for versatile peroxidase. The PAH-degradation products themselves are possible biological inducers [35]. Therefore, complete characterization of these compounds is necessary for a complete assessment of the remediation processes.…”

“…For example, the addition of the mixture containing anthracene, fluoranthene, phenanthrene and pyrene resulted in increased ligninolytic enzyme activity and a significantly higher activity of Mn-independent peroxidase appeared. In the case of individual PAH -pyrene the stimulation of Mn-dependent and Mn-independent peroxidases was also observed [35].…”