title: Engineering yeast with bifunctional minicellulosome and cellodextrin pathway for co-utilization of cellulose-mixed sugars.
abstract: BACKGROUND
  Consolidated bioprocessing (CBP), integrating cellulase production, cellulose saccharification, and fermentation into one step has been widely considered as the ultimate low-cost configuration for producing second-generation fuel ethanol. However, the requirement of a microbial strain able to hydrolyze cellulosic biomass and convert the resulting sugars into high-titer ethanol limits CBP application.
  
  
  RESULTS
  In this work, cellulolytic yeasts were developed by engineering Saccharomyces cerevisiae with a heterologous cellodextrin utilization pathway and bifunctional minicellulosomes. The cell-displayed minicellulosome was two-scaffoldin derived, and contained an endoglucanase and an exoglucanase, while the intracellular cellodextrin pathway consisted of a cellodextrin transporter and a β-glucosidase, which mimicked the unique cellulose-utilization system in Clostridium thermocellum and allowed S. cerevisiae to degrade and use cellulose without glucose inhibition/repression on cellulases and mixed-sugar uptake. Consequently, only a small inoculation of the non-induced yeast cells was required to efficiently co-convert both cellulose and galactose to ethanol in a single-step co-fermentation process, achieving a high specific productivity of ~62.61 mg cellulosic ethanol/g cell·h from carboxymethyl cellulose and ~56.37 mg cellulosic ethanol/g cell·h from phosphoric acid-swollen cellulose.
  
  
  CONCLUSIONS
  Our work provides a versatile engineering strategy for co-conversion of cellulose-mixed sugars to ethanol by S. cerevisiae, and the achievements in this work may further promote cellulosic biofuel production.
authors.affiliation: College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, People's Republic of China ; Beijing Key Laboratory of Bioprocess, Beijing, People's Republic of China.
authors.forename: Li-Hai
authors.initials: LH
authors.lastname: Fan
authors.affiliation: College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, People's Republic of China ; Beijing Key Laboratory of Bioprocess, Beijing, People's Republic of China.
authors.forename: Zi-Jian
authors.initials: ZJ
authors.lastname: Zhang
authors.affiliation: College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, People's Republic of China ; Beijing Key Laboratory of Bioprocess, Beijing, People's Republic of China.
authors.forename: Sen
authors.initials: S
authors.lastname: Mei
authors.affiliation: College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, People's Republic of China ; Beijing Key Laboratory of Bioprocess, Beijing, People's Republic of China.
authors.forename: Yang-Yang
authors.initials: YY
authors.lastname: Lu
authors.affiliation: College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, People's Republic of China ; Beijing Key Laboratory of Bioprocess, Beijing, People's Republic of China.
authors.forename: Mei
authors.initials: M
authors.lastname: Li
authors.affiliation: College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, People's Republic of China ; Beijing Key Laboratory of Bioprocess, Beijing, People's Republic of China.
authors.forename: Zai-Yu
authors.initials: ZY
authors.lastname: Wang
authors.affiliation: College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, People's Republic of China ; Beijing Key Laboratory of Bioprocess, Beijing, People's Republic of China.
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Yang
authors.affiliation: Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH USA.
authors.forename: Shang-Tian
authors.initials: ST
authors.lastname: Yang
authors.affiliation: College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, People's Republic of China ; Beijing Key Laboratory of Bioprocess, Beijing, People's Republic of China.
authors.forename: Tian-Wei
authors.initials: TW
authors.lastname: Tan
keywords: Biofuel; Biomass; Consolidated bioprocessing; Saccharomyces cerevisiae