In the present study, the polysaccharide-hydrolyzing secretomes of Irpex lacteus (Fr.) Fr. (1828) BCC104, Pycnoporus coccineus (Fr.) Bondartsev and Singer (1941) BCC310, and Schizophyllum commune Fr. (1815) BCC632 were analyzed in submerged fermentation conditions to elucidate the effect of chemically and structurally different carbon sources on the expression of cellulases and xylanase. Among polymeric substrates, crystalline cellulose appeared to be the best carbon source providing the highest endoglucanase, total cellulase, and xylanase activities. Mandarin pomace as a growth substrate for S. commune allowed to achieve comparatively high volumetric activities of all target enzymes while wheat straw induced a significant secretion of cellulase and xylanase activities of I. lacteus and P. coccineus. An additive effect on the secretion of cellulases and xylanases by the tested fungi was observed when crystalline cellulose was combined with mandarin pomace. In I. lacteus the cellulase and xylanase production is inducible in the presence of cellulose-rich substrates but is suppressed in the presence of an excess of easily metabolizable carbon source. These enzymes are expressed in a coordinated manner under all conditions studied. It was shown that the substitution of glucose in the inoculum medium with Avicel provides accelerated enzyme production by I. lacteus and higher cellulase and xylanase activities of the fungus. These results add new knowledge to the physiology of basidiomycetes to improve cellulase production.

The potential of wood-rotting and litter-deconstructing basidiomycetes to convert lignocellulose into a wide variety of products has been extensively studied. In particular, wood-rotting basidiomycete secretomes are attracting much attention from researchers and biotechnology companies due to their ability to produce extracellular hydrolytic and oxidative enzymes that effectively degrade cellulose, hemicellulose, and lignin of plant biomass. An analysis of the available literature data shows that Basidiomycota fungi, which are most adapted to the depolymerization of plant polysaccharides, are promising but so far unexploited sources of new hydrolytic enzymes. The review summarizes the latest data on the great variety, common features, and unique properties of individual fungi and the production of cellulases and xylanases by various physiological and ecological groups of basidiomycetes. The most important microbial cellulase-producing strains for submerged and solid-phase fermentation, as well as the main substrates, including the use of agro-industrial waste, are considered. It highlights ways to increase both cellulase and xylanase expression levels and the cost-effectiveness of producing these enzymes for various biotechnological applications. It is anticipated that this review will be particularly useful to novice scientists working in the lignocellulose biorefinery, as it describes current knowledge and issues related to the production and regulation of polysaccharide hydrolyzing enzyme synthesis.

The polysaccharide-hydrolyzing enzymes of Schizophyllum commune BCC 632 have been analyzed in submerged fermentation conditions to elucidate the effect of chemically and structurally different carbon sources on the expression of cellulases and xylanase. Production of cellulase and xylanase by S. commune BCC 632 requires the presence of inducing substrate in the culture medium. Crystalline cellulose appeared to be the best carbon source providing the highest endoglucanase (53.5 U/mL) and total cellulase (9.2 U/mL) activities. In particular, this fungus appeared to be a super-producer of xylanase (636.1 U/mL). Among complex lignocellulosic substrates, mandarin pomace provided high enzyme activity whereas wheat straw appeared to be a poor substrate for both cellulases and xylanase secretion. However, the supplementation of wheat straw-based medium with mandarin pomace or glycerol resulted in a significant secretion of cellulase and xylanase by the fungus. Nevertheless, the addition of 0.5% glucose to the Avicel-containing medium caused short-term catabolite repression of the synthesis of both cellulase and xylanase while the addition of α-deoxy-D-glucose completely prevented enzyme secretion. Extracellular protein electrophoresis and inhibitory assay using cycloheximide and actinomycin D has shown that both cellulase and xylanase are inducible enzymes and subject to catabolite repression by readily metabolizable sugars.