title: Metabolic engineering of Propionibacterium freudenreichii for n-propanol production.
abstract: Propionibacteria are widely used in industry for manufacturing of Swiss cheese, vitamin B₁₂, and propionic acid. However, little is known about their genetics and only a few reports are available on the metabolic engineering of propionibacteria aiming at enhancing fermentative production of vitamin B12 and propionic acid. n-Propanol is a common solvent, an intermediate in many industrial applications, and a promising biofuel. To date, no wild-type microorganism is known to produce n-propanol in sufficient quantities for industrial application purposes. In this study, a bifunctional aldehyde/alcohol dehydrogenase (adhE) was cloned from Escherichia coli and expressed in Propionibacterium freudenreichii. The mutants expressing the adhE gene converted propionyl- coenzyme A, which is the precursor for propionic acid biosynthesis, to n-propanol. The production of n-propanol was limited by NADH availability, which was improved significantly by using glycerol as the carbon source. Interestingly, the improved propanol production was accompanied by a significant increase in propionic acid productivity, indicating a positive effect of n-propanol biosynthesis on propionic acid fermentative production. To our best knowledge, this is the first report on producing n-propanol by metabolically engineered propionibacteria, which offers a novel route to produce n-propanol from renewable feedstock, and possibly a new way to boost propionic acid fermentation.
authors.affiliation: William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 140 West 19th Avenue, Columbus, OH 43210, USA.
authors.forename: Ehab Mohamed
authors.initials: EM
authors.lastname: Ammar
authors.forename: Zhongqiang
authors.initials: Z
authors.lastname: Wang
authors.forename: Shang-Tian
authors.initials: ST
authors.lastname: Yang
mesh_terms: D000433:1-Propanol / Q000378:metabolism*; D005285:Fermentation; D007700:Kinetics; D011424:Propionibacterium / Q000378:metabolism*
chemical_list: D000433:1-Propanol