title: Enhanced 2,3-Butanediol Production by Optimizing Fermentation Conditions and Engineering Klebsiella oxytoca M1 through Overexpression of Acetoin Reductase.
abstract: Microbial production of 2,3-butanediol (2,3-BDO) has been attracting increasing interest because of its high value and various industrial applications. In this study, high production of 2,3-BDO using a previously isolated bacterium Klebsiella oxytoca M1 was carried out by optimizing fermentation conditions and overexpressing acetoin reductase (AR). Supplying complex nitrogen sources and using NaOH as a neutralizing agent were found to enhance specific production and yield of 2,3-BDO. In fed-batch fermentations, 2,3-BDO production increased with the agitation speed (109.6 g/L at 300 rpm vs. 118.5 g/L at 400 rpm) along with significantly reduced formation of by-product, but the yield at 400 rpm was lower than that at 300 rpm (0.40 g/g vs. 0.34 g/g) due to acetoin accumulation at 400 rpm. Because AR catalyzing both acetoin reduction and 2,3-BDO oxidation in K. oxytoca M1 revealed more than 8-fold higher reduction activity than oxidation activity, the engineered K. oxytoca M1 overexpressing the budC encoding AR was used in fed-batch fermentation. Finally, acetoin accumulation was significantly reduced by 43% and enhancement of 2,3-BDO concentration (142.5 g/L), yield (0.42 g/g) and productivity (1.47 g/L/h) was achieved compared to performance with the parent strain. This is by far the highest titer of 2,3-BDO achieved by K. oxytoca strains. This notable result could be obtained by finding favorable fermentation conditions for 2,3-BDO production as well as by utilizing the distinct characteristic of AR in K. oxytoca M1 revealing the nature of reductase.
authors.affiliation: Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea.
authors.forename: Sukhyeong
authors.initials: S
authors.lastname: Cho
authors.affiliation: Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea; Interdisciplinary Program in Agriculture Biotechnology, College of Agriculture and Life science, Seoul National University, Seoul, Republic of Korea.
authors.forename: Taeyeon
authors.initials: T
authors.lastname: Kim
authors.affiliation: Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea; Clean Energy and Chemical Engineering, Korea University of Science and Technology, Daejeon, Republic of Korea.
authors.forename: Han Min
authors.initials: HM
authors.lastname: Woo
authors.affiliation: Department of Chemical and Biomolecular Engineering, Sogang University, Seoul, Republic of Korea.
authors.forename: Jinwon
authors.initials: J
authors.lastname: Lee
authors.affiliation: Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea.
authors.forename: Yunje
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea; Clean Energy and Chemical Engineering, Korea University of Science and Technology, Daejeon, Republic of Korea.
authors.forename: Youngsoon
authors.initials: Y
authors.lastname: Um
mesh_terms: D000429:Alcohol Oxidoreductases / Q000096:biosynthesis* / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D002072:Butylene Glycols / Q000378:metabolism*; D005285:Fermentation; D015870:Gene Expression; D041121:Klebsiella oxytoca / Q000201:enzymology* / Q000235:genetics; D060847:Metabolic Engineering
chemical_list: D001426:Bacterial Proteins; D002072:Butylene Glycols; C026978:2,3-butylene glycol; D000429:Alcohol Oxidoreductases; C019801:butanediol dehydrogenase