Biocatalysis is becoming an increasingly attractive method to achieve enantiopure chemicals, in a cleaner and more environmentally sustainable way. This is in part due to the fact that in most of these reactions, water is used as the solvent primarily because the enzyme catalysts are most stable in this medium. However, some substrates are insoluble or only sparingly soluble in water which can limit the use of these enzymes.
In this work, Lasse Greiner and colleagues from Germany have developed a procedure whereby sparingly water-soluble long-chain ketones can be reduced in a continuous process. The authors used an ionic liquid as a detergent to increase the solubility of these substrates and products, and ultrafiltration in an enzyme membrane reactor was employed to increase the enzyme utilization. A cascade of two enzyme membrane reactors was configured which could run for more than 1000 hours with high turnover numbers and 99.9% enantioselectivity.
Finally, downstream adsorption of the resulting alcohols allowed 90% recycling of the aqueous buffer solution, reducing the E-factor of the process to 13.
This article is currently free to access until the 3rd January 2013!
Enantioselective reduction of sparingly water-soluble ketones: continuous process and recycle of the aqueous buffer system, Susanne Leuchs, Shukrallah Na’amnieh and Lasse Greiner, Green Chem., 2013, DOI: 10.1039/C2GC36558H
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