Alanine production in an H+-ATPase- and lactate dehydrogenase-defective mutant of Escherichia coli expressing alanine dehydrogenase |
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Authors: | Wada Masaru Narita Kotomi Yokota Atsushi |
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Affiliation: | (1) Division of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan |
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Abstract: | Previously, we reported that pyruvate production was markedly improved in TBLA-1, an H+-ATPase-defective Escherichia coli mutant derived from W1485lip2, a pyruvate-producing E. coli K-12 strain. TBLA-1 produced more than 30 g/l pyruvate from 50 g/l glucose by jar fermentation, while W1485lip2 produced only 25 g/l pyruvate (Yokota et al. in Biosci Biotechnol Biochem 58:2164–2167, 1994b). In this study, we tested the ability of TBLA-1 to produce alanine by fermentation. The alanine dehydrogenase (ADH) gene from Bacillus stearothermophilus was introduced into TBLA-1, and direct fermentation of alanine from glucose was carried out. However, a considerable amount of lactate was also produced. To reduce lactate accumulation, we knocked out the lactate dehydrogenase gene (ldhA) in TBLA-1. This alanine dehydrogenase-expressing and lactate dehydrogenase-defective mutant of TBLA-1 produced 20 g/l alanine from 50 g/l glucose after 24 h of fermentation. The molar conversion ratio of glucose to alanine was 41%, which is the highest level of alanine production reported to date. This is the first report to show that an H+-ATPase-defective mutant of E. coli can be used for amino acid production. Our results further indicate that H+-ATPase-defective mutants may be used for fermentative production of various compounds, including alanine. |
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Keywords: | Alanine production Escherichia coli H+-ATPase Alanine dehydrogenase |
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