title: Modular Optimization of a Hemicellulose-Utilizing Pathway in Corynebacterium glutamicum for Consolidated Bioprocessing of Hemicellulosic Biomass.
abstract: Hemicellulose, which is the second most abundant polysaccharide in nature after cellulose, has the potential to become a major feedstock for microbial fermentation to produce various biofuels and chemicals. To utilize hemicellulose economically, it is necessary to develop a consolidated bioprocess (CBP), in which all processes from biomass degradation to the production of target products occur in a single bioreactor. Here, we report a modularly engineered Corynebacterium glutamicum strain suitable for CBP using hemicellulosic biomass (xylan) as a feedstock. The hemicellulose-utilizing pathway was divided into three distinct modules, and each module was separately optimized. In the module for xylose utilization, the expression level of the xylose isomerase (xylA) and xylulokinase (xylB) genes was optimized with synthetic promoters of different strengths. Then, the module for xylose transport was engineered with combinatorial sets of synthetic promoters and heterologous transporters to achieve the fastest cell growth rate on xylose (0.372 h(-1)). Next, the module for the enzymatic degradation of xylan to xylose was also engineered with different combinations of promoters and signal peptides to efficiently secrete both endoxylanase and xylosidase into the extracellular medium. Finally, each optimized module was integrated into a single plasmid to construct a highly efficient xylan-utilizing pathway. Subsequently, the direct production of lysine from xylan was successfully demonstrated with the engineered pathway. To the best of our knowledge, this is the first report of the development of a consolidated bioprocessing C. glutamicum strain for hemicellulosic biomass.
authors.affiliation: Department of Chemical and Biomolecular Engineering, BK21 Plus Program, ‡Institute for the BioCentury, KAIST , 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.
authors.forename: Sung Sun
authors.initials: SS
authors.lastname: Yim
authors.affiliation: Department of Chemical and Biomolecular Engineering, BK21 Plus Program, ‡Institute for the BioCentury, KAIST , 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.
authors.forename: Jae Woong
authors.initials: JW
authors.lastname: Choi
authors.affiliation: Department of Chemical and Biomolecular Engineering, BK21 Plus Program, ‡Institute for the BioCentury, KAIST , 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.
authors.forename: Se Hwa
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Chemical and Biomolecular Engineering, BK21 Plus Program, ‡Institute for the BioCentury, KAIST , 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.
authors.forename: Ki Jun
authors.initials: KJ
authors.lastname: Jeong
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000378:metabolism; D056804:Biofuels; D018533:Biomass; D048230:Corynebacterium glutamicum / Q000201:enzymology / Q000378:metabolism*; D043364:Endo-1,4-beta Xylanases / Q000235:genetics / Q000378:metabolism; D005818:Genetic Engineering; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014990:Xylans / Q000378:metabolism; D014994:Xylose / Q000378:metabolism; D014995:Xylosidases / Q000235:genetics / Q000378:metabolism
chemical_list: D056804:Biofuels; D011134:Polysaccharides; D014990:Xylans; C007916:hemicellulose; D014994:Xylose; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase; D014995:Xylosidases; D043364:Endo-1,4-beta Xylanases; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase
keywords: Corynebacterium glutamicum; consolidated bioprocess; hemicellulose; modular engineering; synthetic promoter