Regular articleChiral diol t-butyl 6-cyano-(3R,5R)-dihydroxylhexanoate synthesis catalyzed by immobilized cells of carbonyl reductase and glucose dehydrogenase co-expression E. coli

•The celite-PEI-GA immobilized CR and GDH co-expression E. coli cells were prepared.•The stability of immobilizate was improved, which can be reused for 7 intermittent batches.•A total of 17.5 g (3R,5R)-2 was synthesized by one g of immobilizates, in a dep > 99.5%.

In our previous work, we constructed a carbonyl reductase (CR) and glucose dehydrogenase (GDH) co-expression strain E. coli BL21(DE3)/pCDFDuet-gdh-cr, and a biocatalytic process of chiral diol t-butyl 6-cyano-(3R,5R)-dihydroxyhexanoate ((3R,5R)-2) was established by using its free cells. Herein, a (3R,5R)-2 process with celite-polyethyleneimine (PEI)-glutaraldehyde (GA) immobilized E. coli BL21(DE3)/pCDFDuet-gdh-cr whole cells was developed for the first time. It was demonstrated that immobilization via cross-linking was preferred, and the optimized immobilization conditions were as follows: 0.6% (w/v) celite, 4% (w/v) PEI and 1% (w/v) GA, pH7. The immobilizate can be used at pH 7.0, 30 °C for intermittent 7 batch, yielding a total of 17.5 g (3R,5R)-2 per gram of celite-PEI-GAimmobilizates in dep (diastereomeric excess) >99.5%. Compared with the free cells, there was a dramatic improvement in celite- PEI-GA immobilizate stability and recyclability. In this way, a promising platform technology based on a combination of cells immobilization and multiple enzymes co-expression is constructed, enabling efficiently converting inexpensive prochiral ketones to high-valued chiral alcohols.

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