The acyl transferase from Mycobacterium smegmatis (MsAcT) catalyses transesterification reactions in aqueous media because of its hydrophobic active site. Aliphatic cyanohydrin and alkyne esters can be synthesised in water with excellent and strikingly opposite enantioselectivity [(R);E>37 and (S);E>100, respectively]. When using this enzyme, the undesired hydrolysis of the acyl donor is an important factor to take into account. Finally, the choice of acyl donor can significantly influence the obtained enantiomeric excesses.magnified image

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Hydroxynitrile lyase from cassava, Manihot esculenta, (MeHNL) catalyzes the formation of (S)‐cyanohydrins from HCN and aldehydes or ketones. Four differently immobilized MeHNLs were prepared: by noncovalent immobilization (celite R‐633), covalent immobilization (cross‐linked enzyme aggregates, CLEA), encapsulation [in a poly(vinyl alcohol) hydrogel Lentikats] and a combination of the above, an unusual immobilization, CLEA encapsulated in a poly(vinyl alcohol) hydrogel. A comparative study of the recyclability of each immobilized MeHNL was performed. Particular attention was paid to the stability and activity of the new immobilized MeHNL–CLEA–Lentikats and to the minimum enzyme loading required to achieve high yields and enantiomeric excesses. MeHNL–CLEA stability was slightly improved by encapsulation into Lentikats and good recyclability rates at low enzyme loading were obtained. However, MeHNL immobilized on celite R‐633 exhibited the best recyclability, giving >95 % conversion and an enantiomeric excess of 99 % during 12 cycles.

Acyltransferase from Mycobacterium smegmatis (MsAcT) immobilised in continuous-flow microchannel reactors with hierarchical pore structure enabled quantitative, full and rapid transesterification of neopentylglycol (NPG) with ethyl acetate in less than one minute.

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