Production of 2,3-butanediol in Saccharomyces cerevisiae by in silico aided metabolic engineering.
BACKGROUND
2,3-Butanediol is a chemical compound of increasing interest due to its wide applications. It can be synthesized via mixed acid fermentation of pathogenic bacteria such as Enterobacter aerogenes and Klebsiella oxytoca. The non-pathogenic Saccharomyces cerevisiae possesses three different 2,3-butanediol biosynthetic pathways, but produces minute amount of 2,3-butanediol. Hence, we attempted to engineer S. cerevisiae strain to enhance 2,3-butanediol production.


RESULTS
We first identified gene deletion strategy by performing in silico genome-scale metabolic analysis. Based on the best in silico strategy, in which disruption of alcohol dehydrogenase (ADH) pathway is required, we then constructed gene deletion mutant strains and performed batch cultivation of the strains. Deletion of three ADH genes, ADH1, ADH3 and ADH5, increased 2,3-butanediol production by 55-fold under microaerobic condition. However, overproduction of glycerol was observed in this triple deletion strain. Additional rational design to reduce glycerol production by GPD2 deletion altered the carbon fluxes back to ethanol and significantly reduced 2,3-butanediol production. Deletion of ALD6 reduced acetate production in strains lacking major ADH isozymes, but it did not favor 2,3-butanediol production. Finally, we introduced 2,3-butanediol biosynthetic pathway from Bacillus subtilis and E. aerogenes to the engineered strain and successfully increased titer and yield. Highest 2,3-butanediol titer (2.29 . l-1) and yield (0.113 g . g-1) were achieved by Δadh1 Δadh3 Δadh5 strain under anaerobic condition.


CONCLUSIONS
With the aid of in silico metabolic engineering, we have successfully designed and constructed S. cerevisiae strains with improved 2,3-butanediol production.
Department of Chemical & Biological Engineering, Korea University, Seoul 136-701, Republic of Korea.
Chiam Yu
CY
Ng
Moo-Young
MY
Jung
Jinwon
J
Lee
Min-Kyu
MK
Oh
D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D053898:Biosynthetic Pathways; D002072:Butylene Glycols / Q000378:metabolism*; D017353:Gene Deletion; D060847:Metabolic Engineering / Q000379:methods*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*
D001426:Bacterial Proteins; D002072:Butylene Glycols; C026978:2,3-butylene glycol; D000426:Alcohol Dehydrogenase