Phytoremediation of diesel-contaminated soil and saccharification of the resulting biomass

In this study, we aimed to identify plant species capable of remediating diesel-contaminated soil and to convert their biomass to bioethanol. Three plant species (Pinus densiflora, Populus tomentiglandulosa, and Thuja orientalis) were grown on an area of soil contaminated with 6000 mg/kg of diesel to assess the effects of addition of a microbial consortium and fertilizer on remediation efficacy. Diesel-contaminated soil resulted in reduced plant biomass for most of the tested plants. However, in diesel-contaminated P. densiflora pots containing the microbial consortium, shoot biomass was greater than that in pots treated with diesel alone. Additionally, fertilizer application was found to be the most important factor for efficient diesel degradation. Plant biomass in diesel-contaminated soil was pretreated and used as a substrate for hydrolysis using lignocellulases from Armillaria gemina, a newly isolated fungal strain. The strain showed the highest β-glucosidase (15 U/mL), cellobiohydrolase (34 U/mL), endoglucanase (146 U/mL), endoxylanase (1270 U/mL), laccase (0.16 U/mL), mannanase (57 U/mL), lignin peroxidase (0.31 U/mL) and filter paper (1.72 U/mL) activities. The highest saccharification yield was obtained with P. densiflora (52%). The A. gemina enzymes hydrolyzed the woody biomass used for phytoremediation and resulted in a high level of reducing sugar (375 mg/g-substrate).