Secretome of the Coprophilous Fungus Doratomyces stemonitis C8, Isolated from Koala Feces

Abstract

Coprophilous fungi inhabit herbivore feces, secreting enzymes to degrade the most recalcitrant parts of plant biomass that have resisted the digestive process. Consequently, the secretomes of coprophilous fungi have high potential to contain novel and efficient plant cell wall degrading enzymes of biotechnological interest. We have used one-dimensional and two-dimensional gel electrophoresis, matrix-assisted laser desorption ionization-time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS/MS), and quadrupole time-of-flight liquid chromatography-tandem mass spectrometry (Q-TOF LC-MS/MS) to identify proteins from the secretome of the coprophilous fungus Doratomyces stemonitis C8 (EU551185) isolated from koala feces. As the genome of D. stemonitis has not been sequenced, cross-species identification, de novo sequencing, and zymography formed an integral part of the analysis. A broad range of enzymes involved in the degradation of cellulose, hemicellulose, pectin, lignin, and protein were revealed, dominated by cellobiohydrolase of the glycosyl hydrolase family 7 and endo-1,4-β-xylanase of the glycosyl hydrolase family 10. A high degree of specialization for pectin degradation in the D. stemonitis C8 secretome distinguishes it from the secretomes of some other saprophytic fungi, such as the industrially exploited T. reesei. In the first proteomic analysis of the secretome of a coprophilous fungus reported to date, the identified enzymes provide valuable insight into how coprophilous fungi subsist on herbivore feces, and these findings hold potential for increasing the efficiency of plant biomass degradation in industrial processes such as biofuel production in the future.