14-12: Supplementation of commercial cellulase cocktails with alpha-xylosidase improves yields of fermentable sugars

Monday, April 29, 2013
Exhibit Hall
Jonathan D. Walton, Melissa S Borrusch, Dina Jabbour and Goutami Banerjee, Great Lakes Bioenergy Research Center and MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI
Although alpha-linked xylose is a major constituent of the xyloglucan hemicelluloses of land plants, secreted alpha-xylosidases have rarely been scientifically described. Aspergillus niger secretes an alpha-xylosidase (AxlA) and its activity and encoding gene were recently characterized. To evaluate the possible utility of AxlA to the lignocellulose biofuels industry, we tested the effect of supplementing commercial enzyme cocktails with AxlA on the release of sugars from several biomass substrates including herbaceous dicotyledons, which have higher xyloglucan levels than cereals. Commercial cellulases alone were ineffective at releasing free Glc or Xyl from pea xyloglucan or tamarind xyloglucan, whereas the sugar yields were stimulated >20-fold by adding AxlA. Supplementation of a 3:1 mixture of CTec2:HTec2 with AxlA enhanced Glc yields from pretreated corn stover from 82% to 88% of theoretical maximum and Xyl yields from 55% to 60%. The positive effect of AxlA supplementation was most apparent at higher CTec2:HTec2 concentrations and longer incubation times. Supplementation of Accellerase 1000 with AxlA improved Glc yields from corn stover from 76% to 85% of theoretical maximum under the same assay conditions. AxlA also enhanced Glc yields from the model forb, Chenopodium album (lamb’s quarters) from 82% to 96% of theoretical maximum. The enhancement of sugar yields by AxlA was not a general protein effect because BSA or IgG at similar concentrations did not affect Glc yields. We conclude that commercial cellulases can be improved by supplementation with AxlA and that doing so might be economically worthwhile at least with some biomass feedstocks.