Improved fermentative gamma-aminobutyric acid production from glucose by the inactivation of respiratory chain components NDH-I and Cytbo3 in Escherichia coli

Available online 7 September 2024 Gamma-aminobutyric acid (GABA), which is synthesized from L-glutamic acid via glutamate decarboxylase (Gad), is used as food, supplements, and biodegradable plastics. Our previous study demonstrated an Escherichia coli mutant (DD) strain, lacking type I NADH dehydrogenase (NDH-I) and cytochrome bo 3 oxidase (Cytbo3), produced 7 g/L glutamic acid on MS1 glucose-minimal medium. In this study, the DD strain was used for improving GABA production. A plasmid (pMBL19-gadB0) expressing a mutated E. coli GadB (Glu89Gln/D452-46 6), retaining activity at neutral pH, was introduced into the DD strain and its parent strain (W1485). The DD strain carrying pMBL19-gadB0 exhibited a twofold increase in GABA production compared to the W1485 strain carrying pMBL19-gadB0. Deleting the C-terminal (D471-511) of GadC antiporter in the DD strain further improved GABA yield to 1.5 g/L when cultured in MS1 glucose-minimal medium. On the other hand, a large amount of glutamic acid produced by the DD strain was not fully converted to GABA, likely due to the inhibition of GadB activity by the accumulation of acetic acid. Although there is room for improvement, these results indicate the efficacy of the D NDH-I D Cyt bo 3 double mutation in augmenting GABA production. (c) 2024, The Society for Biotechnology, Japan. All rights are reserved, including those for text and data mining, AI training, and similar technologies.