, Volume 75, Issue 5, pp 1173-1182
Date: 23 Mar 2007

Anaerobic growth and potential for amino acid production by nitrate respiration in Corynebacterium glutamicum

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Oxygen limitation is a crucial problem in amino acid fermentation by Corynebacterium glutamicum. Toward this subject, our study was initiated by analysis of the oxygen-requiring properties of C. glutamicum, generally regarded as a strict aerobe. This organism formed colonies on agar plates up to relatively low oxygen concentrations (0.5% O2), while no visible colonies were formed in the absence of O2. However, in the presence of nitrate ( \({\text{NO}}^{ - }_{{\text{3}}} \) ), the organism exhibited limited growth anaerobically with production of nitrite ( \({\text{NO}}^{ - }_{{\text{2}}} \) ), indicating that C. glutamicum can use nitrate as a final electron acceptor. Assays of cell extracts from aerobic and hypoxic cultures yielded comparable nitrate reductase activities, irrespective of nitrate levels. Genome analysis revealed a narK2GHJI cluster potentially relevant to nitrate reductase and transport. Disruptions of narG and narJ abolished the nitrate-dependent anaerobic growth with the loss of nitrate reductase activity. Disruption of the putative nitrate/nitrite antiporter gene narK2 did not affect the enzyme activity but impaired the anaerobic growth. These indicate that this locus is responsible for nitrate respiration. Agar piece assays using l-lysine- and l-arginine-producing strains showed that production of both amino acids occurred anaerobically by nitrate respiration, indicating the potential of C. glutamicum for anaerobic amino acid production.