Abstract
1-Hydroxy-2-butanone (HB) is a key intermediate for anti-tuberculosis pharmaceutical ethambutol. Commercially available HB is primarily obtained by the oxidation of 1,2-butanediol (1,2-BD) using chemical catalysts. In present study, seven enzymes including diol dehydrogenases, secondary alcohol dehydrogenases and glycerol dehydrogenase were chosen to evaluate their abilities in the conversion of 1,2-BD to HB. The results showed that (2R, 3R)- and (2S, 3S)-butanediol dehydrogenase (BDH) from Serratia sp. T241 could efficiently transform (R)- and (S)-1,2-BD into HB respectively. Furthermore, two biocatalysts co-expressing (2R, 3R)-/(2S, 3S)-BDH, NADH oxidase and hemoglobin protein in Escherichia coli were developed to convert 1,2-BD mixture into HB, and the transformation conditions were optimized. Maximum HB yield of 341.35 and 188.80 mM could be achieved from 440 mM (R)-1,2-BD and 360 mM (S)-1,2-BD by E. coli (pET-rrbdh-nox-vgb) and E. coli (pET-ssbdh-nox-vgb) under the optimized conditions. In addition, two biocatalysts showed the ability in chiral resolution of 1,2-BD isomers, and 135.68 mM (S)-1,2-BD and 112.43 mM (R)-1,2-BD with the purity of 100% could be obtained from 300 and 200 mM 1,2-BD mixture by E. coli (pET-rrbdh-nox-vgb) and E. coli (pET-ssbdh-nox-vgb), respectively. These results provided potential application for HB production from 1,2-BD mixture and chiral resolution of (R)-1,2-BD and (S)-1,2-BD.
Highlights
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Three enzymes after purification showed different specific activities when 1,2-BD mixture was used as substrate with the coenzyme NAD+ (Table 1), suggesting 1,2-BD might be a substrate for HB production by butanediol dehydrogenase (BDH) enzymes
The results showed that (R)-1,2-BD in 300 mM 1,2-BD mixture could be completely converted into HB by the E. coli biocatalyst, which resulted in 164.21 mM HB and 135.68 mM enantiopure (S)-1,2-BD with 100% purity (Figure 6E and Figure S5)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The BDH enzymes from Serratia marcescens H30 and Paenibacillus polymyxa ATCC 12321 showed the activities for 1,2-pentadiol and 1,2-propanediol as substrates [13,14] These results exhibited a broad substrate spectrum for the diol oxidation by BDH enzymes, which provided application potential for HB production from 1,2-BD. The relative activity of 90%, 60%, and 45% for 1,2-BD as substrate by three GDHs from Schizosaccharomyces pombe, Cellulomonas sp., and Enterobacter aerogenes respectively could be achieved when compared with that of glycerol as substrate [4,21] Both of the two types of enzymes may be used as an alternative enzyme for HB production from 1,2-BD as substrate. Three diol dehydrogenases, three secondary alcohol dehydrogenases, and one glycerol dehydrogenase were chosen to evaluate their abilities in converting 1,2-BD into HB These enzymes consisted of (2S, 3S)-BDH, meso-BDH, (2R, 3R)-BDH, and GDH from Serratia sp. This study provided potential application for HB production from 1,2-BD mixture and chiral resolution of (R)-1,2-BD and (S)-1,2-BD
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