Fungi Useful for the Purification of the Lignin Fraction from Residues of Bioethanol Production

Lignocellulosic residues, deriving from the production of biofuels, represent a precious source and being able to purify and exploit them is crucial for a more sustainable supply of lignin. The aim of this work was to increase the efficiency of the biological treatment of lignocellulosic residues to obtain purified lignin which can be used in biotechnological applications. The study evaluated the activity of two Ascomycota fungal strains on a bioethanol production waste material rich in lignocellulosic residues (LRR). The tested fungi were Trichoderma asperellum 1020, isolated from a hydroponic plant culture and Paecilomyces variotii 1030, isolated from a sample of lignin purified by chemical methods. The degradation ability of the selected fungi was verified by measuring their consumption of reducing sugars over 3 months, while the purification was assessed by measuring the degradation of reducing sugars and the activity of the secretome (endo-β-1,4-glucanase, β-glucosidase, β-1,3-glucanase, endo-1,4-β-xylanase, pectinase). Both strains appear to use almost all the available reducing sugars in the first 4 days after inoculation and a decrease of the reducing sugars up to 70% was obtained in the samples treated with T. asperellum 1020. The quantification of enzymes secreted revealed that P. variotii 1030 has greater potential in the degradation of cellulose and pectin, while T. asperellum 1020 degrades preferably pectin and carbohydrate residues. These strains act on the components of LRR and are particularly promising to processes lignocellulosic residues.