This
work describes the improvement in enantioselectivity on the resolution of
mandelic acid catalyzed by the Candida
rugosa lipase (CRL) immobilized and stabilized on two different ionic
supports. CRL was quickly immobilized on anionic diethylaminoethyl (DEAE)
support and, due to the low content of positive charges on enzyme surface; the
enzyme could only be successfully immobilized on cationic carboxymethyl support
after chemical amination. Immobilized the enzyme presented higher thermal
stability and higher stability to pH than the free enzyme. In relation to the
free-enzyme, the DEAE derivative was 2-fold more stable in acid pH, while the
carboxymethyl derivative was 2-fold more stable in alkaline pH. When incubated at
pH 7.0 and 50 ºC, the carboxymethyl derivative was more stable retaining 80% of
activity even after 7 h incubation, and the DEAE derivative presented half-life
of 6.6 h. Due to this promising characteristics, both CRL derivatives were
evaluated on the hydrolysis of (R,S)-mandelic acid ethyl ester under different
pH. The CRL immobilized on DEAE support presented stereochemical preference for
the R isomer in pH 5.0 and 7.0, while in pH 9.0 the hydrolysis of the S isomer
hydrolysis was faster with a higher E-value of 21.2. On the other hand, the
carboxymethyl derivative showed opposite results regarding stereochemical
preference with higher E-value at pH 5.0 (E > 200) demonstrating excellent
enantioselective transesterification towards the S-isomer of mandelic acid with
a theoretical 50% conversion yield and a 99.9% enantiomeric excess.
Primary Language | English |
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Journal Section | Articles |
Authors | |
Publication Date | June 21, 2019 |
Published in Issue | Year 2019Issue: 5 |