화학공학소재연구정보센터
Process Biochemistry, Vol.80, 43-51, 2019
t-Butyl 6-cyano-(3R, 5R)-dihydroxyhexanoate synthesis via asymmetric reduction by immobilized cells of carbonyl reductase and glucose dehydrogenase co-expression E. coli
Chiral diol t-butyl 6-cyano-(3R,5R)-dihydroxyhexanoate ((3R,5R)-2) is an important building block of atorvastatin calcium. In our previous works, we constructed a glucose dehydrogenase (GDH) and carbonyl reductase (CR) co-expression strain E. coil BL21(DE3)/pCDFDuet-gdh-cr, which was capable for asymmetrically reducing t-butyl 6-cyano-(5R)-hydroxyl-3-oxolhexanoate ((5R)-1) to (3R,5R)-2. In order to increase the stability and re-cyclability of biocatalyst, a combinatorial immobilization technique of activated carbon (AC) adsorption, metal organic framework (MOF) ZIF-8 coating and glutaraldehyde (GA) cross-linking was exploited, and applied to embed the whole cells of E. coli BL21(DE3)/pCDFDuet-gdh-cr (designated as AC-ZIF-8@E. coli-GA). Under the optimized conditions, activity recovery of AC-ZIF-8@E. coli-GA reached 82.6%. AC-ZIF-8@E. coli-GA could be used for intermittent 9 batches, with an overall yield of 23.75 g (3R,5R)-2 per gram of AC-ZIF-8@E. coli-GA in d.e.(P) (diastereomeric excess) > 99.5%. Compared with the free cells and celite-polyethyleneimine-GA immobilized cells of E. coli BL21(DE3)/pCDFDuet-gdh-cr, both stability and recyclability of AC-ZIF-8@E. coli-GA were dramatically improved.