title: Metabolic engineering of Saccharomyces cerevisiae to produce 1-hexadecanol from xylose.
abstract: BACKGROUND
  An advantageous but challenging approach to overcome the limited supply of petroleum and relieve the greenhouse effect is to produce bulk chemicals from renewable materials. Fatty alcohols, with a billion-dollar global market, are important raw chemicals for detergents, emulsifiers, lubricants, and cosmetics production. Microbial production of fatty alcohols has been successfully achieved in several industrial microorganisms. However, most of the achievements were using glucose, an edible sugar, as the carbon source. To produce fatty alcohols in a renewable manner, non-edible sugars such as xylose will be a more appropriate feedstock.
  
  
  RESULTS
  In this study, we aim to engineer a Saccharomyces cerevisiae strain that can efficiently convert xylose to fatty alcohols. To this end, we first introduced the fungal xylose utilization pathway consisting of xylose reductase (XR), xylitol dehydrogenase (XDH), and xylulose kinase (XKS) into a fatty alcohol-producing S. cerevisiae strain (XF3) that was developed in our previous studies to achieve 1-hexadecanol production from xylose at 0.4 g/L. We next applied promoter engineering on the xylose utilization pathway to optimize the expression levels of XR, XDH, and XKS, and increased the 1-hexadecanol titer by 171 %. To further improve the xylose-based fatty alcohol production, two optimized S. cerevisiae strains from promoter engineering were evolved with the xylose as the sole carbon source. We found that the cell growth rate was improved at the expense of decreased fatty alcohol production, which indicated 1-hexadecanol was mainly produced as a non-growth associated product. Finally, through fed-batch fermentation, we successfully achieved 1-hexadecanol production at over 1.2 g/L using xylose as the sole carbon source, which represents the highest titer of xylose-based 1-hexadecanol reported in microbes to date.
  
  
  CONCLUSIONS
  A fatty alcohol-producing S. cerevisiae strain was engineered in this study to produce 1-hexadecanol from xylose. Although the xylose pathway we developed in this study could be further improved, this proof-of-concept study, for the first time to our best knowledge, demonstrated that the xylose-based fatty alcohol could be produced in S. cerevisiae with potential applications in developing consolidated bioprocessing for producing other fatty acid-derived chemicals.
authors.affiliation: Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA. gweihua2@vt.edu.
authors.forename: Weihua
authors.initials: W
authors.lastname: Guo
authors.affiliation: Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA. jysheng@vt.edu.
authors.forename: Jiayuan
authors.initials: J
authors.lastname: Sheng
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA. zhao5@illinois.edu.
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA. xueyang@vt.edu.
authors.forename: Xueyang
authors.initials: X
authors.lastname: Feng
mesh_terms: D061249:Batch Cell Culture Techniques; D019020:Directed Molecular Evolution; D005233:Fatty Alcohols / Q000378:metabolism*; D005285:Fermentation; D060847:Metabolic Engineering / Q000379:methods*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
chemical_list: D005233:Fatty Alcohols; C005031:cetyl alcohol; D014994:Xylose
references.citation: Metab Eng. 2014 Sep;25:20-9
references.pmid: 24930894
references.citation: Metab Eng. 2015 May;29:113-23
references.pmid: 25773521
references.citation: Metab Eng. 2012 Nov;14(6):611-22
references.pmid: 22921355
references.citation: Nucleic Acids Res. 2009 Feb;37(2):e16
references.pmid: 19074487
references.citation: Appl Environ Microbiol. 2003 Apr;69(4):1990-8
references.pmid: 12676674
references.citation: FEMS Yeast Res. 2003 Oct;4(1):69-78
references.pmid: 14554198
references.citation: FEMS Yeast Res. 2005 Jul;5(10):925-34
references.pmid: 15949975
references.citation: Metab Eng. 2015 Jan;27:10-9
references.pmid: 25466225
references.citation: Nucleic Acids Res. 2012 Oct;40(18):e142
references.pmid: 22718979
references.citation: Appl Microbiol Biotechnol. 2013 Aug;97(15):7061-71
references.pmid: 23793343
references.citation: Microb Cell Fact. 2013;12:114
references.pmid: 24245823
references.citation: Appl Environ Microbiol. 2000 Aug;66(8):3381-6
references.pmid: 10919795
references.citation: Mol Biosyst. 2011 Apr;7(4):1056-9
references.pmid: 21327279
references.citation: Trends Ecol Evol. 2008 Oct;23(10):538-45
references.pmid: 18775582
references.citation: Nat Protoc. 2007;2(1):31-4
references.pmid: 17401334
references.citation: Biotechnol Biofuels. 2010 Nov 16;3:24
references.pmid: 21080929
references.citation: Metab Eng. 2013 Nov;20:177-86
references.pmid: 24141053
references.citation: Appl Environ Microbiol. 2013 Feb;79(3):931-41
references.pmid: 23183982
references.citation: Microb Cell Fact. 2012;11:65
references.pmid: 22607313
references.citation: Metab Eng. 2014 Mar;22:10-21
references.pmid: 24333607
references.citation: Proc Natl Acad Sci U S A. 2013 Jan 2;110(1):87-92
references.pmid: 23248280
references.citation: Cell Mol Life Sci. 2012 Aug;69(16):2671-90
references.pmid: 22388689
references.citation: Metab Eng. 2014 Jan;21:103-13
references.pmid: 23899824
references.citation: Proc Natl Acad Sci U S A. 2006 Jul 25;103(30):11206-10
references.pmid: 16837571
references.citation: Biotechnol Bioeng. 2015 Feb;112(2):386-92
references.pmid: 25116045
references.citation: J Ind Microbiol Biotechnol. 2015 Nov;42(11):1463-72
references.pmid: 26318028
references.citation: FEMS Yeast Res. 2012 Aug;12(5):582-97
references.pmid: 22487265
references.citation: Curr Opin Biotechnol. 2011 Dec;22(6):775-83
references.pmid: 21620688
references.citation: Metab Eng. 2014 Jul;24:139-49
references.pmid: 24853351
references.citation: Appl Environ Microbiol. 2004 Jun;70(6):3681-6
references.pmid: 15184173
references.citation: J Ind Microbiol Biotechnol. 2011 Aug;38(8):873-90
references.pmid: 21526386
references.citation: Nat Commun. 2013;4:2580
references.pmid: 24105024
references.citation: Biotechnol Biofuels. 2013 Jul 06;6(1):96
references.pmid: 23830104
references.citation: Biotechnol Biofuels. 2013 Jun 21;6(1):89
references.pmid: 23800147
references.citation: Appl Microbiol Biotechnol. 2004 Feb;63(5):495-509
references.pmid: 14595523
references.citation: Biotechnol Biofuels. 2010 Jun 15;3:13
references.pmid: 20550651