title: Co-expression of two heterologous lactate dehydrogenases genes in Kluyveromyces marxianus for l-lactic acid production.
abstract: Lactic acid (LA) is a versatile compound used in the food, pharmaceutical, textile, leather, and chemical industries. Biological production of LA is possible by yeast strains expressing a bacterial gene encoding l-lactate dehydrogenase (LDH). Kluyveromyces marxianus is an emerging non-conventional yeast with various phenotypes of industrial interest. However, it has not been extensively studied for LA production. In this study, K. marxianus was engineered to express and co-express various heterologous LDH enzymes that were reported to have different pH optimums. Specifically, three LDH enzymes originating from Staphylococcus epidermidis (SeLDH; optimal at pH 5.6), Lactobacillus acidophilus (LaLDH; optimal at pH 5.3), and Bos taurus (BtLDH; optimal at pH 9.8) were functionally expressed individually and in combination in K. marxianus, and the resulting strains were compared in terms of LA production. A strain co-expressing SeLDH and LaLDH (KM5 La+SeLDH) produced 16.0g/L LA, whereas the strains expressing those enzymes individually produced only 8.4 and 6.8g/L, respectively. This co-expressing strain produced 24.0g/L LA with a yield of 0.48g/g glucose in the presence of CaCO3.Our results suggest that co-expression of LDH enzymes with different pH optimums provides sufficient LDH activity under dynamic intracellular pH conditions, leading to enhanced production of LA compared to individual expression of the LDH enzymes.
authors.affiliation: Department of Genetic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors.forename: Jae Won
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Department of Genetic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors.forename: Jung Hoon
authors.initials: JH
authors.lastname: In
authors.affiliation: Department of Genetic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors.forename: Joon-Bum
authors.initials: JB
authors.lastname: Park
authors.affiliation: Department of Genetic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors.forename: Jonghyeok
authors.initials: J
authors.lastname: Shin
authors.affiliation: Biomaterials Lab, Samsung Advanced Institute of Technology, Yongin 446-712, Republic of Korea.
authors.forename: Jin Hwan
authors.initials: JH
authors.lastname: Park
authors.affiliation: Korea Research Institute of Bioscience & Biotechnology, Daejeon 305-806, Republic of Korea.
authors.forename: Bong Hyun
authors.initials: BH
authors.lastname: Sung
authors.affiliation: Korea Research Institute of Bioscience & Biotechnology, Daejeon 305-806, Republic of Korea.
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Sohn
authors.affiliation: Department of Agricultural Biotechnology, Seoul National University, Seoul 151-921, Republic of Korea.
authors.forename: Jin-Ho
authors.initials: JH
authors.lastname: Seo
authors.affiliation: Department of Food Science and Engineering, Ewha Womans University, Seoul 120-750, Republic of Korea.
authors.forename: Jin-Byoung
authors.initials: JB
authors.lastname: Park
authors.affiliation: School of Food Science and Biotechnology, College of Agriculture and Life Sciences, Kyungpook National University, 702-701, Republic of Korea. Electronic address: soorinkim@knu.ac.kr.
authors.forename: Soo Rin
authors.initials: SR
authors.lastname: Kim
authors.affiliation: Department of Genetic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea. Electronic address: dhkweon@skku.edu.
authors.forename: Dae-Hyuk
authors.initials: DH
authors.lastname: Kweon
mesh_terms: D005285:Fermentation; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007716:Kluyveromyces / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D045022:Lactate Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D019344:Lactic Acid / Q000032:analysis / Q000378:metabolism*; D060847:Metabolic Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D011994:Recombinant Proteins; D019344:Lactic Acid; D045022:Lactate Dehydrogenases
keywords: Co-expression; Kluyveromyces marxianus; Lactate dehydrogenase; Lactic acid; Optimal pH