title: Improved fermentative production of gamma-aminobutyric acid via the putrescine route: Systems metabolic engineering for production from glucose, amino sugars, and xylose.
abstract: Gamma-aminobutyric acid (GABA) is a non-protein amino acid widespread in Nature. Among the various uses of GABA, its lactam form 2-pyrrolidone can be chemically converted to the biodegradable plastic polyamide-4. In metabolism, GABA can be synthesized either by decarboxylation of l-glutamate or by a pathway that starts with the transamination of putrescine. Fermentative production of GABA from glucose by recombinant Corynebacterium glutamicum has been described via both routes. Putrescine-based GABA production was characterized by accumulation of by-products such as N-acetyl-putrescine. Their formation was abolished by deletion of the spermi(di)ne N-acetyl-transferase gene snaA. To improve provision of l-glutamate as precursor 2-oxoglutarate dehydrogenase activity was reduced by changing the translational start codon of the chromosomal gene for 2-oxoglutarate dehydrogenase subunit E1o to the less preferred TTG and by maintaining the inhibitory protein OdhI in its inhibitory form by changing amino acid residue 15 from threonine to alanine. Putrescine-based GABA production by the strains described here led to GABA titers up to 63.2 g L-1in fed-batch cultivation at maximum volumetric productivities up to 1.34 g L-1h-1, the highest volumetric productivity for fermentative GABA production reported to date. Moreover, GABA production from the carbon sources xylose, glucosamine, and N-acetyl-glucosamine that do not have competing uses in the food or feed industries was established. Biotechnol. Bioeng. 2017;114: 862-873. © 2016 Wiley Periodicals, Inc.
authors: Faculty of Biology and CeBiTec, Genetics of Prokaryotes, Bielefeld University, Universitätsstr. 25, Bielefeld 33615, Germany.
authors: João M P
authors: JM
authors: Jorge
authors: Faculty of Biology and CeBiTec, Genetics of Prokaryotes, Bielefeld University, Universitätsstr. 25, Bielefeld 33615, Germany.|evocatal GmbH, Monheim, Germany.
authors: Anh Q D
authors: AQ
authors: Nguyen
authors: Faculty of Biology and CeBiTec, Genetics of Prokaryotes, Bielefeld University, Universitätsstr. 25, Bielefeld 33615, Germany.
authors: Fernando
authors: F
authors: Pérez-García
authors: evocatal GmbH, Monheim, Germany.
authors: Stefanie
authors: S
authors: Kind
authors: Faculty of Biology and CeBiTec, Genetics of Prokaryotes, Bielefeld University, Universitätsstr. 25, Bielefeld 33615, Germany.
authors: Volker F
authors: VF
authors: Wendisch
mesh_terms: D000606:Amino Sugars; D061249:Batch Cell Culture Techniques; D018533:Biomass; D048230:Corynebacterium glutamicum / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D060847:Metabolic Engineering / Q000379:methods*; D011700:Putrescine / Q000378:metabolism*; D049490:Systems Biology / Q000379:methods*; D014994:Xylose / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000606:Amino Sugars; D005680:gamma-Aminobutyric Acid; D014994:Xylose; D005947:Glucose; D011700:Putrescine
keywords: Corynebacterium glutamicum; GABA production; alternative carbon sources; metabolic engineering; putrescine route; transport engineering