Light-regulated synthesis of extra- and intracellular enzymes related to wood degradation by the white rot fungus Cerrena unicolor during solid-state fermentation on ash sawdust-based medium.

The light-dependent metabolism of the white rot basidiomycete Cerrena unicolor FCL139 has already been demonstrated using transcriptomic and Biolog-based approaches. To further analyze the influence of light on C. unicolor wood degradation, we measured the activity of an array of CAZymes (carbohydrate-active enzymes) and enzymes involved in the redox system of fungal cells associated with lignolysis. Extra- and intracellular enzymatic extracts were obtained from solid-state ash sawdust C. unicolor cultures cultivated for 14 days under red, blue, green, or white light conditions, or in the dark. Light greatly influenced the synthesis of MnP, total cellulases, endo-1,4-ß-glucanase, endo-1,4-ß-xylanase, catalase, and superoxide dismutase. The production of MnP and catalase was evidently stimulated by white light. It is also worth noticing that blue light caused a gradual increase in the activity of total cellulases throughout the entire period of C. unicolor growth. Moreover, endo-1,4-ß-glucanase showed the highest activity on day 13 of fungus cultivation and the production of laccase and ß-glucosidase appeared to be the least influenced by light. However, the strongest activity of the endo-1,4-ß-xylanase was observed in the dark. It seemed that light not only influenced the regulation of the synthesis of the wood-degrading enzymes at different levels, but also acted indirectly by affecting production of enzymes managing harmful lignin by-products causing oxidative stress. The ability of the fungus to decompose woody plant material is clearly influenced by environmental factors.

Lignin degradation: microorganisms, enzymes involved, genomes analysis and evolution.

Extensive research efforts have been dedicated to describing degradation of wood, which is a complex process; hence, microorganisms have evolved different enzymatic and non-enzymatic strategies to utilize this plentiful plant material. This review describes a number of fungal and bacterial organisms which have developed both competitive and mutualistic strategies for the decomposition of wood and to thrive in different ecological niches. Through the analysis of the enzymatic machinery engaged in wood degradation, it was possible to elucidate different strategies of wood decomposition which often depend on ecological niches inhabited by given organism. Moreover, a detailed description of low molecular weight compounds is presented, which gives these organisms not only an advantage in wood degradation processes, but seems rather to be a new evolutionatory alternative to enzymatic combustion. Through analysis of genomics and secretomic data, it was possible to underline the probable importance of certain wood-degrading enzymes produced by different fungal organisms, potentially giving them advantage in their ecological niches. The paper highlights different fungal strategies of wood degradation, which possibly correlates to the number of genes coding for secretory enzymes. Furthermore, investigation of the evolution of wood-degrading organisms has been described.

Characterization of Cellobiose Dehydrogenase from a Biotechnologically Important Cerrena unicolor Strain.

Cellobiose dehydrogenase (CDH), a secreted flavocytochrome produced by a number of wood-degrading fungi, was detected in the culture supernatant of a biotechnologically important strain of Cerrena unicolor grown in a modified cellulose-based liquid medium. The enzyme was purified as two active fractions: CuCDH-FAD (flavin domain) (1.51-fold) with recovery of 8.35 % and CuCDH (flavo-heme enzyme) (21.21-fold) with recovery of 73.41 %. As CDH from other wood-rotting fungi, the intact form of cellobiose dehydrogenase of C. unicolor is a monomeric protein containing one flavin and one heme b with molecular mass 97 kDa and pI = 4.55. The enzyme is glycosylated (8.2 %) mainly with mannose and glucosamine residues. Moreover, the cellobiose dehydrogenase gene cdh1 and its corresponding cDNA from the fungus C. unicolor were isolated, cloned, and characterized. The 2316-bp full-length cDNA of cdh1 encoded a mature CDH protein containing 771 amino acids preceded by a signal peptide consisting of 18 amino acids. Moreover, both active fractions were characterized in terms of kinetics, temperature and pH optima, and antioxidant properties.

Characterization of cellobiose dehydrogenase and its FAD-domain from the ligninolytic basidiomycete Pycnoporus sanguineus.

Cellobiose dehydrogenase (CDH), an extracellular flavocytochrome produced by several wood-degrading fungi, was detected in the culture supernatant of the selective delignifier Pycnoporus sanguineus maintained on a cellulose-based liquid medium. Cellobiose dehydrogenase was purified as two active fractions: CDH1-FAD (flavin domain) (40.4 fold) with recovery of 10.9% and CDH1 (flavo-heme enzyme) (54.7 fold) with recovery of 9.8%. As determined by SDS-PAGE, the molecular mass of the purified enzyme was found to be 113.4kDa and its isoelectric point was 4.2, whereas these values for the FAD-domain were 82.7kDa and pI=6.7. The carbohydrate content of the purified enzymes was 9.2%. In this work, the cellobiose dehydrogenase gene cdh1 and its corresponding cDNA from fungus P. sanguineus were isolated, cloned, and characterized. The 2310bp full-length cDNA of cdh1 encoded a mature CDH protein containing 769 amino acids, which was preceded by a signal peptide of 19 amino acids. Moreover, both active fractions were characterized in terms of kinetics, temperature and pH optima, and antioxidant properties.