Ligninolytic enzymes production during polycyclic aromatic hydrocarbons degradation: effect of soil pH, soil amendments and fungal co-cultivation

Abstract

Soil microorganisms play an important role in the degradation of PAHs and use various metabolic pathways for this process. The effect of soil pH, different soil amendments and the co-cultivation of fungi on the degradation of PAHs in soil and on the activity of ligninolytic enzymes was evaluated. For that purpose, three fungi were studied: Trichoderma viride, Penicillium chrysogenum and Agrocybe aegerita. Biodegradation assays with a mixture of 200 ppm PAHs (fluorene, pyrene, chrysene, and benzo[a]pyrene-50 ppm each) were set up at room temperature for 8 weeks. The maximum laccase activity by solid state fermentation-SSF (7.43 U/g) was obtained by A. aegerita on kiwi peels with 2 weeks and the highest manganese peroxidase activity (7.21 U/g) was reached in 4 weeks, both at pH 7. Fluorene, pyrene, and benzo[a]pyrene achieved higher degradation rates in soil at pH 5, while chrysene was more degradable at pH 7. About 85-90% of the PAHs were degraded by fungal remediation. The highest degradation of fluorene was achieved by co-cultivation of A. aegerita and P. chrysogenum, remaining 14% undegradable. Around 13% of pyrene stay undegradable by A. aegerita and T. viride and by A. aegerita and P. chrysogenum, both systems supported in kiwi peels, while 11% of chrysene remained in soil by the cocultivation of these fungi, supported by peanut shells.Regarding benzo[a]pyrene, 13% remained in soil after treatment with A. aegerita. Despite the increase in degradation of some PAHs with co-cultivation, higher enzyme production during degradation was observed when fungi were cultivated alone.

Bioprospection of ligninolytic enzymes from marine origin filamentous fungi

“…has the capacity to produce manganese peroxidase in a solid culture medium, however it did not show activity for Lacase. The same result was found by Vipotnik et al (2021), where it was not possible to detect Lac for P. chrysogenum in 2 weeks of incubation in solid fermentation under the influence of pH 7.…”

Variations in lignin monomer contents and stable hydrogen isotope ratios in methoxy groups during the biodegradation of garden biomass

“…Usually, a multi-species symbiotic mixture is the best approach to promote diverse enzyme production and synergistic effects 43 . This could be why co-cultivation of different species can trigger more responses to chemical signals than would be possible with a single fungus or bacterium 44 .

Figure 1 The changes in degradation weight loss ( DWL ) and net degradation loss ( NDL , the difference in the DWL value between the inoculation experiment and the uninoculated control) for garden biomass during the 15-day experiments, with measurements at 2-day intervals.

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Soil pH and Soluble Organic Matter Shifts Exerted by Heating Affect Microbial Response

“…Apart from the natural adaptation of the original microbial community that certainly could be affecting CFU proliferation, fire-induced pH changes could affect some enzymatic activities essential for degrading compounds that could be limiting microbial growth in this treatment, such as PAHs. In fact, fungal population appears to play an important role in PAH degradation, with an important role in its lignolytic activities as laccase [ 80 , 81 ]. The pH effect on PAHs’ degradation appears to depend on different factors, such as organism species or the PAH compound.…”