title: Introduction of a bacterial acetyl-CoA synthesis pathway improves lactic acid production in Saccharomyces cerevisiae.
abstract: Acid-tolerant Saccharomyces cerevisiae was engineered to produce lactic acid by expressing heterologous lactate dehydrogenase (LDH) genes, while attenuating several key pathway genes, including glycerol-3-phosphate dehydrogenase1 (GPD1) and cytochrome-c oxidoreductase2 (CYB2). In order to increase the yield of lactic acid further, the ethanol production pathway was attenuated by disrupting the pyruvate decarboxylase1 (PDC1) and alcohol dehydrogenase1 (ADH1) genes. Despite an increase in lactic acid yield, severe reduction of the growth rate and glucose consumption rate owing to the absence of ADH1 caused a considerable decrease in the overall productivity. In Δadh1 cells, the levels of acetyl-CoA, a key precursor for biologically applicable components, could be insufficient for normal cell growth. To increase the cellular supply of acetyl-CoA, we introduced bacterial acetylating acetaldehyde dehydrogenase (A-ALD) enzyme (EC 1.2.1.10) genes into the lactic acid-producing S. cerevisiae. Escherichia coli-derived A-ALD genes, mhpF and eutE, were expressed and effectively complemented the attenuated acetaldehyde dehydrogenase (ALD)/acetyl-CoA synthetase (ACS) pathway in the yeast. The engineered strain, possessing a heterologous acetyl-CoA synthetic pathway, showed an increased glucose consumption rate and higher productivity of lactic acid fermentation. The production of lactic acid was reached at 142g/L with production yield of 0.89g/g and productivity of 3.55gL(-1)h(-1) under fed-batch fermentation in bioreactor. This study demonstrates a novel approach that improves productivity of lactic acid by metabolic engineering of the acetyl-CoA biosynthetic pathway in yeast.
authors.affiliation: Biomaterials Laboratory, Material Research Center, Samsung Advanced Institute of Technology, Gyeonggi-do, Republic of Korea.
authors.forename: Ji-Yoon
authors.initials: JY
authors.lastname: Song
authors.affiliation: Biomaterials Laboratory, Material Research Center, Samsung Advanced Institute of Technology, Gyeonggi-do, Republic of Korea.
authors.forename: Joon-Song
authors.initials: JS
authors.lastname: Park
authors.affiliation: Biomaterials Laboratory, Material Research Center, Samsung Advanced Institute of Technology, Gyeonggi-do, Republic of Korea.
authors.forename: Chang Duk
authors.initials: CD
authors.lastname: Kang
authors.affiliation: Biomaterials Laboratory, Material Research Center, Samsung Advanced Institute of Technology, Gyeonggi-do, Republic of Korea.
authors.forename: Hwa-Young
authors.initials: HY
authors.lastname: Cho
authors.affiliation: Biomaterials Laboratory, Material Research Center, Samsung Advanced Institute of Technology, Gyeonggi-do, Republic of Korea.
authors.forename: Dongsik
authors.initials: D
authors.lastname: Yang
authors.affiliation: Biomaterials Laboratory, Material Research Center, Samsung Advanced Institute of Technology, Gyeonggi-do, Republic of Korea.
authors.forename: Seunghyun
authors.initials: S
authors.lastname: Lee
authors.affiliation: Biomaterials Laboratory, Material Research Center, Samsung Advanced Institute of Technology, Gyeonggi-do, Republic of Korea. Electronic address: km3.cho@samsung.com.
authors.forename: Kwang Myung
authors.initials: KM
authors.lastname: Cho
mesh_terms: D000105:Acetyl Coenzyme A / Q000096:biosynthesis / Q000235:genetics; D000445:Aldehyde Oxidoreductases / Q000096:biosynthesis / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics; D019344:Lactic Acid / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D019344:Lactic Acid; D000105:Acetyl Coenzyme A; D000445:Aldehyde Oxidoreductases; C018699:aldehyde dehydrogenase (NAD(P)+)
keywords: Acetyl-CoA; Acetylating acetaldehyde dehydrogenase; Alcohol dehydrogenase; Lactic acid; Metabolic engineering; Saccharomyces cerevisiae