The Carbon Source Controls the Secretion and Yield of Polysaccharide-Hydrolyzing Enzymes of Basidiomycetes

• Main Authors: Eka Metreveli, Tamar Khardziani, Vladimir Elisashvili
• Format: Article
• Language: English
• Published: MDPI AG 2021-09-01
• Series: Biomolecules
• Subjects: wood-rotting basidiomycetes; carbon source; cellulase; regulation of synthesis; saccharification
• Online Access: https://www.mdpi.com/2218-273X/11/9/1341

In the present study, the polysaccharide-hydrolyzing secretomes of <i>Irpex lacteus</i> (Fr.) Fr. (1828) BCC104, <i>Pycnoporus coccineus</i> (Fr.) Bondartsev and Singer (1941) BCC310, and <i>Schizophyllum commune</i> 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 <i>S. commune</i> 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>I. lacteus</i> and <i>P. coccineus</i>. 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>I. lacteus</i> 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>I. lacteus</i> and higher cellulase and xylanase activities of the fungus. These results add new knowledge to the physiology of basidiomycetes to improve cellulase production.