Fate of the Oxygen Atoms in the Diol-Dehydratase-Catalyzed Dehydration ofmeso-Butane-2,3-diol

Abstract

18 O-Substituted propane-1,2-diols and meso-butane-1,2-diols were synthesized and fed to growing cells of Lactobacillus brevis. Propan-1-ol and butan-2-ol, prepared from such diols through diol-dehydratase-catalyzed dehydration followed by intracellular reduction, were analyzed for their 18 O-content. For each propane-1,2-diol enantiomer, partial retention or complete loss of the isotope appeared to be related to the mode of substrate binding. Specific retention of the O-atom linked to the (R)-configured C-atom of meso-butane-1,2-diol indicates that the diol dehydratase handles this substrate like (R)-propane-1,2-diol.

Transformation of Biomass into Commodity Chemicals Using Enzymes or Cells

“…Subsequent enzymatic reduction by NAD-dependent alcohol dehydrogenase yields 2-butanol ( Figure 8). 135,136 Patents of DuPont describe E. coli strains which have been metabolically engineered for 2-butanol production according to the aforementioned pathway. 133,137 The highest reported concentration of 2-butanol is only 0.034 g/L, with a yield on glucose below 0.01 g/g and a productivity of 1.4 mg/(L h).…”

“…Certain strains of Lactobacillus can dehydrate 2,3-butanediol to an enol, which isomerizes spontaneously to 2-butanone. Subsequent enzymatic reduction by NAD dependent alcohol dehydrogenase yields 2-butanol (Figure ). ,

8 Pathways via acetolactate. Compounds in boldface are treated in the text.

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One-pot Multi-enzyme Cascade Synthesis of Bifunctional Compounds from Vegetable Oils

“…Multi-enzyme cascades are becoming a revolutionary tool for the selective synthesis of functional molecules [11]. One-pot biocatalytic processes offer multiple advantages, such as no need to isolate/purify reaction intermediates, reduced environmental impact, and improved atomic economy [12]. Bifunctional compounds derived from renewable resources have attracted increasing attention due to their potential to reduce harmful greenhouse gas emissions and circumvent the rising price of fossil raw materials, while also completely avoiding the use of increasingly expensive precious metal catalysts and the need for metal recovery [13].…”