Polycyclic aromatic hydrocarbons degradation by marine-derived basidiomycetes: optimization of the degradation process

ABSTRACT Pyrene and benzo[a]pyrene (BaP) are high molecular weight polycyclic aromatic hydrocarbons (PAHs) recalcitrant to microbial attack. Although studies related to the microbial degradation of PAHs have been carried out in the last decades, little is known about degradation of these environmental pollutants by fungi from marine origin. Therefore, this study aimed to select one PAHs degrader among three marine-derived basidiomycete fungi and to study its pyrene detoxification/degradation. Marasmiellus sp. CBMAI 1062 showed higher levels of pyrene and BaP degradation and was subjected to studies related to pyrene degradation optimization using experimental design, acute toxicity, organic carbon removal (TOC), and metabolite evaluation. The experimental design resulted in an efficient pyrene degradation, reducing the experiment time while the PAH concentration applied in the assays was increased. The selected fungus was able to degrade almost 100% of pyrene (0.08 mg mL-1) after 48 h of incubation under saline condition, without generating toxic compounds and with a TOC reduction of 17%. Intermediate metabolites of pyrene degradation were identified, suggesting that the fungus degraded the compound via the cytochrome P450 system and epoxide hydrolases. These results highlight the relevance of marine-derived fungi in the field of PAH bioremediation, adding value to the blue biotechnology.

Anaerobic biodegradation of benzo(a)pyrene by a novel Cellulosimicrobium cellulans CWS2 isolated from polycyclic aromatic hydrocarbon-contaminated soil

Abstract Cellulosimicrobium cellulans CWS2, a novel strain capable of utilizing benzo(a)pyrene (BaP) as the sole carbon and energy source under nitrate-reducing conditions, was isolated from PAH-contaminated soil. Temperature and pH significantly affected BaP biodegradation, and the strain exhibited enhanced biodegradation ability at temperatures above 30 °C and between pH 7 and 10. The highest BaP removal rate (78.8%) was observed in 13 days when the initial BaP concentration was 10 mg/L, and the strain degraded BaP at constant rate even at a higher concentration (50 mg/L). Metal exposure experimental results illustrated that Cd(II) was the only metal ion that significantly inhibited biodegradation of BaP. The addition of 0.5 and 1.0 g/L glucose enhanced BaP biodegradation, while the addition of low-molecular-weight organic acids with stronger acidity reduced BaP removal rates during co-metabolic biodegradation. The addition of phenanthrene and pyrene, which were degraded to some extent by the strain, showed no distinct effect on BaP biodegradation. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that the five rings of BaP opened, producing compounds with one to four rings which were more bioavailable. Thus, the strain exhibited strong BaP degradation capability and has great potential in the remediation of BaP-/PAH-contaminated environments.

Modulatory effects of different doses of alpha-tocopherol on benzo(a)pyrene-DNA adduct formation in the pulmonary tissue of cigarette smoke inhaling mice.

Cigarette smoke (CS) has been established as one of the major risk factors for many pathologies including lung cancer in humans and experimental animals. In view of the discrepancy about the role of alpha-tocopherol (AT) in carcinogenesis, the present study was designed to investigate the effects of different doses of AT on benzo(a)pyrene-DNA [B(a)P-DNA] adduct formation in lungs of CS inhaling mice. Extent of carcinogen-DNA adduct formation has been considered as an index for carcinogenesis. Feeding of 35 IU AT/kg body weight increased B(a)P-DNA adducts formation significantly whereas feeding of 5 IU AT/kg body weight did not altered much the B(a)P-DNA adduct levels when both were compared to the control counterparts. With CS inhalation, the B(a)P-DNA adducts formation increased in all the groups when compared to their respective sham counterparts. Interestingly, in CS exposed groups, there was least increase in B(a)P-DNA adducts formation in 5 IU AT/kg fed animals followed by the control and 35 IU AT/kg body weight fed groups respectively. The results suggest that higher doses of AT accentuate DNA adduct formation in CS inhaling mice.