Abstract
An efficient and easy-to-perform method was developed for immobilization of CaLB on mesoporous aminoalkyl polymer supports by bisepoxide activation. Polyacrylate resins (100–300 µm; ~50 nm pores) with different aminoalkyl functional groups (ethylamine: EA and hexylamine: HA) were modified with bisepoxides differing in the length, rigidity and hydrophobicity of the units linking the two epoxy functions. After immobilization, the different CaLB preparations were evaluated using the lipase-catalyzed kinetic resolution (KR) of racemic 1-phenylethanol (rac-1) in batch mode and in a continuous-flow reactor as well. Catalytic activity, enantiomer selectivity, recyclability, and the mechanical and long-term stability of CaLB immobilized on the various supports were tested. The most active CaLB preparation (on HA-resin activated with 1,6-hexanediol diglycidyl ether—HDGE) retained 90% of its initial activity after 13 consecutive reaction cycles or after 12 month of storage at 4 °C. The specific rate (rflow), enantiomer selectivity (E) and enantiomeric excess (ee) achievable with the best immobilized CaLB preparations were studied as a function of temperature in kinetic resolution of rac-1 performed in continuous-flow packed-bed bioreactors. The optimum temperature of the most active HA-HDGE CaLB in continuous-flow mode was 60 °C. Although CaLB immobilized on the glycerol diglycidyl ether (GDGE)-activated EA-resin was less active and less selective, a much higher optimum temperature (80 °C) was observed with this form in continuous-flow mode KR of rac-1.
Highlights
Lipases are ubiquitous enzymes which can be found in animals, plants, fungi and bacteria [1,2].Naturally, lipases catalyze the hydrolysis of esters formed of glycerol and long-chain fatty acids [3,4].under particular conditions, they can catalyze esterification and transesterification [5] with high activity, specificity and selectivity
Selection and Bisepoxide Activation of Carriers Used for Covalent Immobilization of Candida antarctica lipase B (CaLB)
Our results indicated that immobilization yields with the other two bisepoxides (CHDGE, Our were results indicated that immobilization yields withother the other two bisepoxides (CHDGE, OurHDGE)
Summary
Lipases are ubiquitous enzymes which can be found in animals, plants, fungi and bacteria [1,2].Naturally, lipases catalyze the hydrolysis of esters formed of glycerol and long-chain fatty acids [3,4].under particular conditions, they can catalyze esterification and transesterification [5] with high activity, specificity and selectivity. Lipases are ubiquitous enzymes which can be found in animals, plants, fungi and bacteria [1,2]. Lipases catalyze the hydrolysis of esters formed of glycerol and long-chain fatty acids [3,4]. Lipases represent a significant class of industrially relevant enzymes [6]. Lipases represent a peculiar mechanism of action, the so called interfacial activation [7,8]. Due to a loop containing α-helicoidal elements that covers the active site, a large proportion of lipases have two different conformations (the closed and the open forms) [4,9]. The equilibrium is shifted towards the water soluble closed form and the active site is secluded
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