Abstract
Acetoin is widely used in food and cosmetic industry as taste and fragrance enhancer. For acetoin production in this study, Saccharomyces cerevisiae JHY605 was used as a host strain, where the production of ethanol and glycerol was largely eliminated by deleting five alcohol dehydrogenase genes (ADH1, ADH2, ADH3, ADH4, and ADH5) and two glycerol 3-phosphate dehydrogenase genes (GPD1 and GPD2). To improve acetoin production, acetoin biosynthetic genes from Bacillus subtilis encoding α-acetolactate synthase (AlsS) and α-acetolactate decarboxylase (AlsD) were overexpressed, and BDH1 encoding butanediol dehydrogenase, which converts acetoin to 2,3-butanediol, was deleted. Furthermore, by NAD+ regeneration through overexpression of water-forming NADH oxidase (NoxE) from Lactococcus lactis, the cofactor imbalance generated during the acetoin production from glucose was successfully relieved. As a result, in fed-batch fermentation, the engineered strain JHY617-SDN produced 100.1 g/L acetoin with a yield of 0.44 g/g glucose.
Highlights
Acetoin is widely used in food and cosmetic industry as taste and fragrance enhancer
Most of commercial acetoin is produced by chemical synthesis, but the use of such non-natural acetoin is restricted in some applications, especially in food and cosmetic industry, because of safety concerns
Butanediol dehydrogenase-blocked B. subtilis (JNA-UD-6), isolated after mutagenesis using UV irradiation with diethyl sulfate, showed a 24.3% increase in acetoin production and a 39.8% decrease in 2,3-butanediol production compared with the parental strain in batch fermentation, and produced 53.9 g/L acetoin after 144 h fermentation in fed-batch fermentation[9]
Summary
Acetoin is widely used in food and cosmetic industry as taste and fragrance enhancer. We developed S. cerevisiae strain for efficient production of 2,3-butanediol by introducing heterologous acetoin biosynthetic pathway from B. subtilis, overexpressing 2,3-butanediol dehydrogenase, and eliminating major byproduct pathways involved in ethanol and glycerol production[14]. The cofactor imbalance generated during 2,3-butanediol production in the engineered strain was restored by overexpressing water-forming NADH oxidase from Lactococcus lactis.
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