title: Genetic engineering of Ketogulonigenium vulgare for enhanced production of 2-keto-L-gulonic acid.
abstract: Folate derivatives are crucial growth factors for Ketogulonigenium vulgare which is used in mixed culture with Bacillus megaterium for the industrial production of 2-keto-L-gulonic acid (2-KGA), the precursor of L-ascorbic acid (L-AA) or vitamin C (Vc). To improve the growth and 2-KGA production, five genes involved in folate biosynthesis identified in a folate gene cluster from Lactococcus lactis MG1363, including folB, folKE, folP, folQ and folC, were over-expressed in K. vulgare. Intracellular folate concentration in the recombinant strain harboring folate biosynthesis genes cluster under the control of P(sdh) (sorbose dehydrogenase gene sdh promoter from K. vulgare) was 8 times higher than that of the wildtype K. vulgare DSM 4025 (P<0.001). In shake flask studies, the cell density and 2-KGA production of the recombinant K. vulgare Rif (pMCS2PsdhfolBC) were increased by 18% (P<0.001) and 14% (P<0.001), respectively, under a relatively stable pH 7 condition. In fermentor studies, enhancements around 25% cell density (P<0.001) and approximately 35% 2-KGA productivity (P<0.001) were observed in comparison with the controls without over-expressing the folate biosynthesis genes. This was the first successful study of metabolic engineering on K. vulgare for enhanced 2-KGA production.
authors.affiliation: Dept Biological Sciences and Biotechnology, MOE Key Lab. Bioinformatics (& System Biology), Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Cai
authors.forename: Mei-Qing
authors.initials: MQ
authors.lastname: Yuan
authors.forename: Zheng-Jun
authors.initials: ZJ
authors.lastname: Li
authors.forename: Jin-Chun
authors.initials: JC
authors.lastname: Chen
authors.forename: Guo-Qiang
authors.initials: GQ
authors.lastname: Chen
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D001410:Bacillus megaterium / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors; D005285:Fermentation; D005492:Folic Acid / Q000096:biosynthesis / Q000235:genetics*; D007218:Industrial Microbiology; D013294:Lactococcus lactis / Q000235:genetics; D060847:Metabolic Engineering; D041902:Rhodobacteraceae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013400:Sugar Acids / Q000737:chemistry / Q000378:metabolism*; D019076:Transgenes
chemical_list: D013400:Sugar Acids; D005492:Folic Acid; C011491:provitamin C; D001205:Ascorbic Acid