The influence of hydroxypropyl-β-cyclodextrin on the enantioselective hydrolysis of 2-amino phenylpropionitrile catalyzed by recombinant nitrilase

Background: Hydrolysis of 2-amino phenylpropionitrile by nitrilase is a fundamental biochemical reaction that produces chiral phenylalanine. For practical application of this biochemical reaction, researchers have attempted to improve enzyme enantioselectivity and the reaction rate. Results: The substrate concentration was increased from 100 to 200 mM without substrate inhibition because of the formation of a substrate-hydroxypropyl-β-cyclodextrin (HP-β-CD) complex. Meanwhile, the activity of recombinant nitrilase increased 2.5 times because the addition of HP-β-CD solubilized hydrophobic substrates in the aqueous system. Furthermore, the formation of the substrate-HP-β-CD inclusion improved the enantioselectivity of the enzymatic reaction toward producing L-phenylalanine (L-Phe). The enantiomeric excess (e.e.) value of L-Phe increased from 65% to 83% when the conversion rate reached 50%. Conclusions: The recombinant nitrilase enantioselectively hydrolyzed 2-amino phenylpropionitrile to produce L-Phe. The addition of HP-β-CD to the reaction system enhanced the solubility and bioavailability of hydrophobic substrates as well as the enantioselectivity. The results showed that this additive has potential advantages in biochemical reactions of hydrophobic substrates, particularly for enantioselective biosynthesis.