Abstract Detail

Lignocellulose Deconstruction by Fungi

Walton, Jonathan [1], Ye, Zhuoliang [1], Zheng, Yun [2], Jabbour, Dina [1], Storms, Reginald [2], Borrusch, Melissa [1].

Mining fungal genomic diversity for novel enzymes for biomass deconstruction.

Enzymatic conversion of lignocellulosic materials to fermentable sugars is a limiting step in the production of biofuels from biomass. Approaches to produce better enzyme cocktails include identification of either new accessory enzymes or better versions of existing enzymes. Combining enzymes from different microbial sources is one way to identify synergistic enzymes. Extracts of the thermophilic fungus Sporotrichum thermophile (synonym Myceliophthora thermophila) gave synergistic release of glucose (Glc) and xylose (Xyl) from pretreated corn stover when combined with an 8-component synthetic cocktail of enzymes from Trichoderma reesei. The S. thermophile extracts were fractionated and an enhancing factor identified as endo-β1,4- glucanase (StCel5A or EG2) of subfamily 5 of Glycosyl Hydrolase family 5 (GH5_5). In a multi-component optimization experiment in which the source of the Cel5A was the only variable, reactions containing StCel5A consistently yielded more Glc and Xyl than reactions containing the ortholog from T. reesei, TrCel5A. The two enzymes had earlier been shown to have similar kinetic parameters when assayed on pure cellulose, and they also have similar temperature and pH optima. When tested on multiple substrates, both enzymes preferred lichenan over other forms of β1,4-linked glucan, but StCel5A had a broader substrate range, being also active on xylan, arabinoxylan, mannan, and galactomannan. Phylogenetically, StCel5A, TrCel5A, and other fungal enzymes in GH5_5 sort into two clades, with StCel5A and TrCel5A belonging to different clades. Structural differences with a potential to account for the differences in performance between StCel5A and TrCel5A were identified, including a loop near the active site of TrCel5A and more Trp residues in the active cleft of StCel5A. Superior biomass-degrading enzymes can be identified by exploring taxonomic diversity combined with assays in the context of realistic enzyme combinations and realistic substrates. One factor contributing to improved performance might be altered substrate range.

1 - Michigan State University, Department of Energy Great Lakes Bioenergy Research Center, 210 Plant Biology Building, E. Lansing, 48824, USA
2 - Concordia University, Centre for Structural and Functional Genomics, Montreal, Canada

Keywords:
cellulase
xylanase
corn stover.

Presentation Type: Symposium or Colloquium Presentation
Session: SY9
Location: Room 104 AB/Kellogg Hotel and Conference Center
Date: Wednesday, June 11th, 2014
Time: 3:30 PM
Number: SY9006
Abstract ID:74
Candidate for Awards:None