Biotransformation of 2-(2’acetoxyethyl)cyclohexanoneinto R-lipoic acid precursor, R-7-(2’-acetoxyethyl)-2-oxepanone with recombinant Corynebacterium glutamicum

Abstract

Enantioselective oxygenation of 2-(2’-acetoxyethyl)cyclohexanone into R-lipoic acid precursor, R-7-(2’-acetoxyethyl)-2-oxepanone has been investigated with recombinant Corynebacterium glutamicum expressing the chnB gene encoding cyclohexanone monooxygenase (CHMO) of Acinetobacter calcoaceticus NCIMB 9871. The recombinant biocatalyst produced R-7-(2’-acetoxyethyl)-2-oxepanone at a rate of over 60 U/g CDW (3.6 mmol/g CDW/h, 0.67 g/g CDW/h) in a whole-cell assay. The biocatalytic activity was maintained over 12 U/g CDW at a substrate concentration of over 25 g/L in the medium, pointing to high catalytic stability against substrate toxicity. Furthermore, biotransformation in a fed-batch culture mode allowed the biocatalyst to produce R-7-(2’-acetoxyethyl)-2-oxepanone at over 6.2 g/L in the medium. The specific and volumetric oxidation activity was 0.09 g/g CDW/h (8.14U/g CDW) and 277 U/L, respectively. These results indicate that the C. glutamicum-based biocatalyst is efficient for the selective oxygenation of 2-(2’-acetoxyethyl) cyclohexanone into R-7-(2’-acetoxyethyl)-2-oxepanone.;Acinetobacter calcoaceticus NCIMB 9871 유래의 cyclohexanone monooxygenase gene (chnB)이 발현된 재조합 Corynebacterium glutamicum의 생촉매 효율을 조사하였다. 유가식 배양에 기초한 생물전환에서 cyclohexanone으로부터 ε-caprolactone을 18.1 g/l로 생산할 수 있었다. Specific and volumetric productivities는 각각 0.13 g/g dry cells/h (19.3 U/g of dry cells) 와 1.34 g/L/h (196 U/L)이었다. 이는 유사한 반응 환경에서 A. calcoaceticus 유래의 chnB를 발현하는 재조합 Escherichia coli BL21 (DE3)의 결과와 비교하여 각각 6배와 1.6배 이상 높다. C. glutamicum 전세포 촉매의 Baeyer-Villiger oxidation 반응을 R-lipoic acid 전구체 생산에 응용하였을 때 유가식 배양에 기초한 생물전환에서 2-(2’-acetoxyethyl)cyclohexanone으로부터 R-7-(2’-acetoxyethyl)-2-oxepanone을 6.2 g/l로 생산할 수 있었다. 이 때 specific and volumetric productivities는 각각 0.09 g /g of dry cells/ h (8.14 U/g of dry cells) 와 3.1 g /L/h (277 U/L) 이었다. 종합적으로 재조합 C. glutamicum은 Baeyer-Villiger oxidation를 위한 뛰어난 차세대 생촉매라고 사료된다.