title: In silico aided metabolic engineering of Klebsiella oxytoca and fermentation optimization for enhanced 2,3-butanediol production.
abstract: Klebsiella oxytoca naturally produces a large amount of 2,3-butanediol (2,3-BD), a promising bulk chemical with wide industrial applications, along with various byproducts. In this study, the in silico gene knockout simulation of K. oxytoca was carried out for 2,3-BD overproduction by inhibiting the formation of byproducts. The knockouts of ldhA and pflB genes were targeted with the criteria of maximization of 2,3-BD production and minimization of byproducts formation. The constructed K. oxytoca ΔldhA ΔpflB strain showed higher 2,3-BD yields and higher final concentrations than those obtained from the wild-type and ΔldhA strains. However, the simultaneous deletion of both genes caused about a 50 % reduction in 2,3-BD productivity compared with K. oxytoca ΔldhA strain. Based on previous studies and in silico investigation that the agitation speed during 2,3-BD fermentation strongly affected cell growth and 2,3-BD synthesis, the effect of agitation speed on 2,3-BD production was investigated from 150 to 450 rpm in 5-L bioreactors containing 3-L culture media. The highest 2,3-BD productivity (2.7 g/L/h) was obtained at 450 rpm in batch fermentation. Considering the inhibition of acetoin for 2,3-BD production, fed-batch fermentations were performed using K. oxytoca ΔldhA ΔpflB strain to enhance 2,3-BD production. Altering the agitation speed from 450 to 350 rpm at nearly 10 g/L of acetoin during the fed-batch fermentation allowed for the production of 113 g/L 2,3-BD, with a yield of 0.45 g/g, and for the production of 2.1 g/L/h of 2,3-BD.
authors.affiliation: Research and Development Center, GS Caltex Corporation, 104-4 Munji-dong, Yuseong-gu, Daejeon, 305-380, Republic of Korea.
authors.forename: Jong Myoung
authors.initials: JM
authors.lastname: Park
authors.forename: Hyohak
authors.initials: H
authors.lastname: Song
authors.forename: Hee Jong
authors.initials: HJ
authors.lastname: Lee
authors.forename: Doyoung
authors.initials: D
authors.lastname: Seung
mesh_terms: D061249:Batch Cell Culture Techniques; D019149:Bioreactors; D002072:Butylene Glycols / Q000378:metabolism*; D003198:Computer Simulation; D005285:Fermentation; D017353:Gene Deletion; D055786:Gene Knockout Techniques; D005798:Genes, Bacterial / Q000235:genetics; D041121:Klebsiella oxytoca / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000172:deficiency / Q000235:genetics; D060847:Metabolic Engineering
chemical_list: D002072:Butylene Glycols; C026978:2,3-butylene glycol; D007770:L-Lactate Dehydrogenase