The E-value of CALB is Influenced by R-Alcohols

A possible explanation was that the effect was connected to the changing concentration of the enantiomeric esters. However, no effect on E was observed when enantiopure (R)-lb, the faster reacting enantiomer of the butanoate of 1-phenoxy- 

The reason for adding a different but structurally related (R)-alcohol was that the analysis and E-value calculations would be influenced by the added (R)-alcohol 

Lower panel E-values at different degrees of conversion in hydrolysis of the corresponding butanoates 1b, 2b, 3b, and 4b catalyzed by Novozym 435. 

It was also surprising that the f -value in the case of (R)-l-phenoxy-2-hexanol R)-Sa) increased and also dropped to the low level quickly after addition. It has been shown that 5a is esterified by vinyl butanoate and CALB with almost no selectivity and with a low rate [14]. For that reason, it seems unlikely that the disappearance of the selectivity enhancement was only due to esterification of the alcohol. However, it is possible that the enantiopure alcohols after addition were bound to the enzyme and after a while brought into the bulk solution by the solvent. The observed quick decrease of effect after addition may therefore be a combination of the removal of the (R)-alcohol by esterification or by solvation. 

Since this effect was observed with the immobilized preparation of CALB (Novozym 435) it was interesting to perform the same reactions with pure protein preparations of CALB to see if the immobilization of the enzyme influenced the changing f -value. The formulated CALB Novozym 525 F is a water solution of CALB containing 1-10% pure protein. After freeze drying at -80 °C this dry protein 

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