|Van Gool, Martine|
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2013
Publication Date: 3/26/2013
Citation: Toth, K., Van Gool, M., Schols, H., Samuels, G., Gruppen, H., Szakacs, G. 2013. Diversity in production of xyaln-degrading enzymes among species belonging to the Trichoderma section Longibrachiatum. BioEnergy Research. 6(2):631-643. Interpretive Summary: Use of raw material such as wheat, straw, and corn fiber for biofuels requires enzymatic breakdown of these raw materials. Fungi produce enzymes that can do this efficiently. For years one fungal isolate had been used for this purpose. In this study isolates known to be related to a group of fungi that produce such enzymes were identified and tested for biodegradation. Many of the closely related isolates were equally good or better at degrading these substrates. This research will be used to determine the most effective fungi to degrade raw materials for the development of biofuels.
Technical Abstract: Xylan is an important part of plant biomass and represents a renewable raw material for biorefineries. Contrary to cellulose, the structure of hemicellulose is quite complex. Therefore, the biodegradation of xylan needs the cooperation of many enzymes. For industrial production of xylanase multienzyme complexes (cocktails) and selected monocomponent xylanases, different Trichoderma reesei mutants and recombinants are used. T. reesei QM 6a (wild-type parent of best existing mutants) was selected as a starting material in the 1960s when the modem in-depth analytical methods were not yet in use. Therefore, screening of fungi genetically close to T. reesei in biodegradation of xylan may have a scientific value. Fifteen different strains from Trichoderma section Longibrachiatum have been tested for extracellular xylan-degrading enzyme production on three carbon sources (wheat straw, corn fiber, and eucalyptus wood) in shake flask cultivation. The enzyme activities were evaluated by traditional colorimetric enzyme assays and by HPLC and matrix assisted laser desorption/ioniza-tion time-of-flight mass spectrometry. Degradation of xylan was studied on four different xylan-rich model substrates. T. reesei CPK 155, Trichoderma parareesei TUB F-2535, and Trichoderma gracile TUB F-2543 isolates were equally good or better in degradation of the wheat arabinoxylan (WAX) and corn fiber alcohol insoluble solids as hydolysis substrates than the well-known T. reesei QM 6a and RUT C30 strains. Though Trichoderma saturnisporum ATCC 18903 gave relatively low volumetric enzyme activities by traditional colorimetric assays, it could release quite large amounts of hydrolysis products (mono- and oligosacchar¬ides) from WAX. Therefore, these fungi may be potential candidates for further experiments. Enzyme production on wheat straw and corn fiber carbon sources was more effective than on eucalyptus wood.