a-hydroxy ketones (HK) and 1,2-diols are important building blocks for fine chemical synthesis. Here, we describe the R-selective 2,3-butanediol dehydrogenase from B. clausii DSM 8716 T (BcBDH) that belongs to the metal-dependent medium chain dehydrogenases/reductases family (MDR) and catalyzes the selective asymmetric reduction of prochiral 1,2-diketones to the corresponding HK and, in some cases, the reduction of the same to the corresponding 1,2-diols. Aliphatic diketones, like 2,3-pentanedione, 2,3-hexanedione, 5-methyl-2,3-hexanedione, 3,4-hexanedione and 2,3-heptanedione are well transformed. In addition, surprisingly alkyl phenyl dicarbonyls, like 2-hydroxy-1-phenylpropan-1-one and phenylglyoxal are accepted, whereas their derivatives with two phenyl groups are not substrates.
Supplementation of Mn 2+(1 mM) increases BcBDH's activity in biotransformations. Furthermore, the biocatalytic reduction of 5-methyl-2,3-hexanedione to mainly 5-methyl-3-hydroxy-2-hexanone with only small amounts of 5-methyl-2-hydroxy-3-hexanone within an enzyme membrane reactor is demonstrated.
Stereopure aliphatic
diols are an interesting class of compounds
because of their potential applications as precursors for chemical
catalysts, for high-value polymers, or as precursors for cyclic acetals.
We present a simultaneous enzymatic two-step, one-pot cascade for
the synthesis of vicinal diols with excellent de and ee values with
the exemplary reaction system from butanal to (4S,5S)-octanediol. This reaction is restricted by
an unfavorable reaction equilibrium. For an intensification of the
reaction toward higher conversions in equilibrium and increased space
time yields (STY), aqueous, microaqueous, and biphasic reaction systems
for in situ product removal (ISPR) were experimentally
investigated and compared. Process concepts for the purification of
(4S,5S)-octanediol from each reaction
system were developed and assessed in terms of product-specific energy
demand. The two-phase reaction system for in situ product removal is favorable for the enzymatic reactions in terms
of yield and STY at different time points. In comparison to the aqueous
and microaqueous reaction systems, the specific energy demand for
(4S,5S)-octanediol recovery is drastically
reduced by approximately a factor of seven when performing ISPR using
a biphasic system in comparison to an aqueous reaction system.
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