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Lecitase Ultra (Leci) was immobilized on Immobead-350 (IB-350) activated with epoxy (EPO), amino-divinylsulfone (DVS) or amino-glutaraldehyde (GLU) groups. Leci-GLU had 27% more activity versus p-nitro-phenyl butyrate (p-NPB) than Leci-EPO, after 3 h of immobilization using 100 mg of enzyme/g of support (immobilization yield was 84.1%, expressed activity versus p-NPB was around 10%), the covalent immobilization was show for Leci-GLU and Leci-DVS. After 10 consecutive cycles of p-NPB hydrolysis, its activity remained unaltered. Leci-GLU was the most stable preparation at 65 °C and pH 7 (29 folds more stable than the free enzyme) and in the presence of 30% acetonitrile at 30 °C and pH 7 (almost 2 folds more stable than the free enzyme). Very interestingly, the activity versus methyl mandelate and synthesis of benzyl acetate was quite high. Although the other biocatalysts had preference for the S-methyl mandelate, Leci-GLU preferred the R-isomer at pHs 5 (VR/VS = 6.6) and 7 (VR/VS = 3.5). In the enzymatic synthesis of benzyl acetate, the most active biocatalyst was also Leci-GLU (2.1 U/mg), being almost 2 folds more active than Leci-DVS. According to the results, it was concluded that the Lecitase immobilization on IB-350 using different chemistries greatly influenced its catalytic properties. |
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