Amino acids are basic materials constitute proteins and essential nutrients for living organisms. The materials have been commercially utilized as additives in dietary supplements, infusion solutions, and livestock feeds. Nowadays amino acids have been mainly produced by microbial fermentation from sugarcane; however more effective and environmental-friendly process, such as from lignocellulose biomass, has recently received large attention to reduce the negative environmental impact.

We have studied to breed effective amino acid-producing strains by metabolic engineering in addition to utilization of lignocellulose biomass. L-Alanine and L-valine synthesis reactions originally require NADPH as a reducing cofactor. In contrast, we modified cofactor requirement of the enzyme to NADH, and introduced amino acid dehydrogenases, which catalyze the amination reaction using NH₃ as an amino-group donor and NADH. As a result, redox imbalance in the overall synthesis reactions is solved, so that amino acid productions with higher productivity and yield under oxygen deprivation are achieved.

Alanine

<L-Alanine production under oxygen deprivation>

Valine

<L-Valine production under oxygen deprivation>