A NOVEL REACTOR CONCEPT FOR THE ENZYMATIC REDUCTION OF POORLY SOLUBLEKETONES

Reductions of poorly soluble ketones often suffer from low total turno ver numbers conferring to the coenzyme and large volumes which are nee ded for the conversion. The novel emulsion membrane reactor overcomes these limitations. From an emulsion consisting of an organic substrate and an aqueous buffer phase, the aqueous phase is separated selective ly by using a hydrophilic ultrafiltration membrane and fed to a subseq uent enzyme membrane reactor. The product outflow is recirculated to t he emulsion stirred vessel and, due to the partition coefficients, the aqueous phase is recharged with substrate while the product is extrac ted. This new reactor concept will be compared to the classical enzyme membrane reactor. The latter was operated under the same conditions o ver a period of 4 months at a space-time yield of 21.2 g l(-1) day(-1) . As a model system the enantioselective reduction of 2-octanone to (S )-2-octanol (ee > 99.5%) is used, carried out by a carbonyl reductase from Candida parapsilosis. NADH is regenerated by formate dehydrogenas e from Candida boidinii. In comparison to the classical enzyme membran e reactor the total turnover number could be increased by a factor 9 u sing the novel emulsion membrane reactor. (C) 1998 Elsevier Science B. V.