Enzymatic synthesis of optically pure cyanohydrins in microchannels using a crude cell lysate

The synthesis of optically pure cyanohydrins using a crude cell lysate containing the enzyme hydroxynitrile lyase (HNL) was studied in a microreactor in an aqueous–organic biphasic system. Different aldehyde substrates were selected to be converted to their corresponding cyanohydrins. It was successfully demonstrated that this crude cell lysate could readily be applied as a biocatalyst in a microchannel without clogging the channels. The biocatalytic activity toward the different substrates could rapidly be investigated with only small quantities of enzyme needed, compared to batch scale screening. Furthermore, the optimal contact between two immiscible phases in a microreactor resulted in enzymatic reactions with a high initial reaction rate and enantioselectivity, comparable to a batchwise process in which optimized conditions were achieved by vigorous stirring. Thus, performing the selected enzymatic reaction in a microreactor is a facile and cost efficient screening method leading to results which can be directly translated to batchwise processes.