title: Direct conversion of xylan to ethanol by recombinant Saccharomyces cerevisiae strains displaying an engineered minihemicellulosome.
abstract: Arabinoxylan is a heteropolymeric chain of a β-1,4-linked xylose backbone substituted with arabinose residues, representing a principal component of plant cell walls. Here we developed recombinant Saccharomyces cerevisiae strains as whole-cell biocatalysts capable of combining hemicellulase production, xylan hydrolysis, and hydrolysate fermentation into a single step. These strains displayed a series of uni-, bi-, and trifunctional minihemicellulosomes that consisted of a miniscaffoldin (CipA3/CipA1) and up to three chimeric enzymes. The miniscaffoldin derived from Clostridium thermocellum contained one or three cohesin modules and was tethered to the cell surface through the S. cerevisiae a-agglutinin adhesion receptor. Up to three types of hemicellulases, an endoxylanase (XynII), an arabinofuranosidase (AbfB), and a β-xylosidase (XlnD), each bearing a C-terminal dockerin, were assembled onto the miniscaffoldin by high-affinity cohesin-dockerin interactions. Compared to uni- and bifunctional minihemicellulosomes, the resulting quaternary trifunctional complexes exhibited an enhanced rate of hydrolysis of arabinoxylan. Furthermore, with an integrated d-xylose-utilizing pathway, the recombinant yeast displaying the bifunctional minihemicellulosome CipA3-XynII-XlnD could simultaneously hydrolyze and ferment birchwood xylan to ethanol with a yield of 0.31 g per g of sugar consumed.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, IL, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Sun
authors.forename: Fei
authors.initials: F
authors.lastname: Wen
authors.forename: Tong
authors.initials: T
authors.lastname: Si
authors.forename: Jian-He
authors.initials: JH
authors.lastname: Xu
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhao
mesh_terms: D001089:Arabinose / Q000378:metabolism; D001709:Biotechnology / Q000379:methods; D044603:Cellulosomes / Q000235:genetics / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005818:Genetic Engineering / Q000379:methods; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D014990:Xylans / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D014990:Xylans; D000431:Ethanol; C085118:arabinoxylan; D014994:Xylose; D001089:Arabinose; D006026:Glycoside Hydrolases; C023305:hemicellulase