title: Increasing proline and myo-inositol improves tolerance of Saccharomyces cerevisiae to the mixture of multiple lignocellulose-derived inhibitors.
abstract: BACKGROUND
  The development of robust microbes with tolerance to the combined lignocellulose-derived inhibitors is critical for the efficient cellulosic ethanol production. However, the lack of understanding on the inhibition mechanism limited the rational engineering of tolerant strain. Here, through the metabolomic analysis of an adaptation process of Saccharomyces cerevisiae to representative inhibitors, i.e., furfural, acetic acid and phenol (FAP), we figured out the new candidates for improving inhibitor tolerance.
  
  
  RESULTS
  After metabolomic analysis, proline and myo-inositol were identified as the potential metabolites responsible for strain tolerance to inhibitors. The deletion of genes involved in proline or myo-inositol synthesis weakened strain tolerance against FAP stress. On the contrary, the addition of proline or myo-inositol in medium exerted a protective effect on cell growth under FAP stress. Furthermore, the enhancement of proline or myo-inositol synthesis by overexpressing key gene PRO1 or INO1 conferred yeast strain significantly increased FAP tolerance. All the recombinant strains finished the fermentation within 60 h under FAP stress, while the control strain was still in the lag phase. Meanwhile, it was found that the intracellular level of reactive oxygen species (ROS) under FAP condition was decreased with the increase of proline content, suggesting the function of proline as a ROS scavenger to protect strains from inhibitor damage.
  
  
  CONCLUSIONS
  Increasing proline and myo-inositol were uncovered as the new determinants for improving strain tolerance to FAP under the guidance of metabolomics. Meanwhile, this study displayed the powerful application of metabolomics to develop rational strategies to increase stress tolerance and provided valuable insights into the design of recombinant microbes for the complex traits.
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, 300072 People's Republic of China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072 People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, 300072 People's Republic of China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072 People's Republic of China.
authors.forename: Xue
authors.initials: X
authors.lastname: Bai
authors.affiliation: School of Management and Economics, Tianjin University, Tianjin, 300072 People's Republic of China.
authors.forename: Dong-Fang
authors.initials: DF
authors.lastname: Chen
authors.affiliation: School of Management and Economics, Tianjin University, Tianjin, 300072 People's Republic of China.
authors.forename: Fu-Zan
authors.initials: FZ
authors.lastname: Chen
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, 300072 People's Republic of China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072 People's Republic of China.
authors.forename: Bing-Zhi
authors.initials: BZ
authors.lastname: Li
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, 300072 People's Republic of China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072 People's Republic of China.
authors.forename: Ying-Jin
authors.initials: YJ
authors.lastname: Yuan
keywords: Lignocellulose-derived inhibitors; Metabolomics; Myo-inositol; Proline; Synthetic biology; Tolerance