Abstract
A triple mutant of NADP(H)-dependent malate dehydrogenase from thermotolerant Thermococcus kodakarensis has an altered cofactor preference for NAD+, as well as improved malate production compared to wildtype malate dehydrogenase. By combining mutant malate dehydrogenase with glucose dehydrogenase from Sulfolobus solfataricus and NAD+/NADH in a closed reaction environment, gluconate and malate could be produced from pyruvate and glucose. After 3 h, the yield of malate was 15.96 mM. These data demonstrate the feasibility of a closed system capable of cofactor regeneration in the production of platform chemicals.
Highlights
Platform chemicals are molecules that can be used to make a variety of industrially valuable products including solvents, polymers, pharmaceuticals and foods [1]
Four-carbon diacids can be converted into 1,4-butanediol which can be further converted into high-value products such as tetrahydrofuran, an important material for polymer production
The current commercial production of malic acid is via the chemical hydration of petrochemically derived maleic/fumaric acid [7], but advances in the field of metabolic engineering have renewed interest in its bio-based production [8]
Summary
Platform chemicals are molecules that can be used to make a variety of industrially valuable products including solvents, polymers, pharmaceuticals and foods [1]. While recent advances have enabled the use of renewable approaches on an industrial scale (such as the production of polylactide and polyethylene from ethylene and biomass-derived lactic acid [4]), the sustainable production of a wider range of platform chemicals is a priority given global concerns about the environment, limited resources, and high oil prices [3,5]. Along with other four-carbon diacids (such as succinic and fumaric acids), was reported as one of the top value-added chemicals from biomass in a 2004 U.S Department of Energy report [6]. The current commercial production of malic acid is via the chemical hydration of petrochemically derived maleic/fumaric acid [7], but advances in the field of metabolic engineering have renewed interest in its bio-based production [8]. Natural high-capacity malic acid producers such as Aspergillus flavus are not well-suited to industrial use due to their physiological constraints [3] and the associated generation of aflatoxin (a carcinogen)
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