Abstract
Backgroundl-Ornithine is a non-protein amino acid with extensive applications in medicine and the food industry. Currently, l-ornithine production is based on microbial fermentation, and few microbes are used for producing l-ornithine owing to unsatisfactory production titer.ResultsIn this study, Corynebacterium glutamicum S9114, a high glutamate-producing strain, was developed for l-ornithine production by pathway engineering. First, argF was deleted to block l-ornithine to citrulline conversion. To improve l-ornithine production, ncgl1221 encoding glutamate transporter, argR encoding arginine repressor, and putP encoding proline transporter were disrupted. This base strain was further engineered by attenuating oxoglutarate dehydrogenase to increase l-ornithine production. Plasmid-based overexpression of argCJBD operon and lysine/arginine transport protein LysE was tested to strengthen l-ornithine synthesis and transportation. This resulted in efficient l-ornithine production at a titer of 18.4 g/L.ConclusionThese results demonstrate the potential of Corynebacterium glutamicum S9114 for efficient l-ornithine production and provide new targets for strain development.
Highlights
We systematically developed a new strain, C. glutamicum S9114, for l-ornithine production (Fig. 1)
Because l-ornithine is an intermediate metabolite of l-arginine synthesis derived from l-glutamate, C. glutamicum S9114 was considered a favorable host for the development of l-ornithine-producing strains
Inactivation of ArgF resulted in a high l-ornithine production titer in C. glutamicum S9114
Summary
Corynebacterium glutamicum, an aerobic gram-positive actinomycete capable of secreting glutamate under biotin limitation or in the presence of penicillin, has longterm applications in the industrial production of various valuable metabolites, including amino acids besides glutamate such as arginine, lysine, ornithine, and alanine [1,2,3,4]; diamines such as putrescine [5, 6] and cadaverine [7]; dicarboxylic acids such as succinate [8,9,10]; diols such as 1,3-propanediol [11] and 1,2-propanediol [12]; and terpenes such as pinene and carotenoid [13]. L-Ornithine is an important constituent of the urea cycle and can be further converted to l-citrulline and l-arginine. In this pathway, l-glutamate is converted to l-ornithine by ArgC, ArgJ, ArgB, and ArgD, which are expressed as an operon and are regulated by the arginine repressor, ArgR.
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