SIZE="-1">D-Amino acid oxida
se (DAAO) wa
s u
sed to
study the oxidative deamination of racemic mixture
sof
D,
L-methionine in it
s soluble and immobilized form
s and thu
s obtain the corre
sponding
s/gifchar
s/alpha.gif" BORDER=0>-ketoacid. The
soluble enzyme form wa
s obtained from a
Trigonopsis variabilis CBS 4095 extract,free of
L-amino acid oxida
se, and wa
s co-immobilized with a 200-fold exce
ss of catala
se toavoid the unde
sirable
side reaction of H
2O
2 with the
s/gifchar
s/alpha.gif" BORDER=0>-keto acid, which would otherwi
se renderit
s corre
sponding decarboxylated acid, the 3-methylthiopropionic acid (MTPA). With thi
sbiocataly
st, quantitative conver
sion (>98%) of
D-methionine into the
s/gifchar
s/alpha.gif" BORDER=0>-keto acid 4-methylthio-2-oxobutyric acid (MTOB) and into MTPA wa
s achieved u
sing 5 mg·mL
-1 of biocataly
st at pH8.0, 25
s/entitie
s/deg.gif">C, and pure oxygen at 3 vvm. A
stirred tank reactor with in
situ product removal(STR-ISPR) wa
s developed to avoid conver
sion of MTOB into MTPA. The reaction mediumwa
s re-circulated through a
strong anion exchange column (Amberlite IRA-400). Thi
s re
sultedin the complete removal of MTOB from the reaction medium. After the reaction, the reactionproduct
s were eluted
sequentially with water (
L-methionine), 10 mM HCl (MTPA), and 0.5 MHCl (MTOB). After elution, MTOB wa
s cry
stallized to it
s sodium
salt.