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Continuous production of ( R )‐phenylacetylcarbinol in an enzyme‐membrane reactor using a potent mutant of pyruvate decarboxylase from Zymomonas mobilis
Author(s) -
Goetz Günter,
Iwan Peter,
Hauer Bernhard,
Breuer Michael,
Pohl Martina
Publication year - 2001
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.1122
Subject(s) - zymomonas mobilis , chemistry , yield (engineering) , pyruvate decarboxylase , substrate (aquarium) , acetaldehyde , benzaldehyde , pyruvic acid , membrane reactor , enzyme , biochemistry , membrane , fermentation , ethanol , ethanol fuel , catalysis , biology , materials science , ecology , metallurgy , alcohol dehydrogenase
The optimization of a continuous enzymatic reaction yielding ( R )‐phenylacetylcarbinol (PAC), an intermediate of the L‐ephedrine synthesis, is presented. We compare the suitability of three pyruvate decarboxylases (PDC), PDC from Saccharomyces cerevisiae , PDC from Zymomonas mobilis , and a potent mutant of the latter, PDC W392M , with respect to their application in the biotransformation using acetaldehyde and benzaldehyde as substrates. Among these, the mutant enzyme was the most active and most stable one. The reaction conditions of the carboligation reaction were investigated by determining initial rate velocities with varying substrate concentrations of both aldehydes. From the resulting data a kinetic model was inferred which fits the experimental data with sufficient reliability to deduce the optimal concentrations of both substrates for the enzymatic process. The results demonstrate that the carboligation is most efficiently performed using a continuous reaction system and feeding both aldehydes in equimolar concentration. Initial studies using a continuously operated enzyme‐membrane reactor gave ( R )‐PAC with a space–time yield of 81 g L ‐1 · d ‐1 using a substrate concentration of 50 mM of both aldehydes. The yield was easily increased by cascadation of enzyme‐membrane reactors. The new strategy allows the synthesis of ( R )‐PAC from cheap substrates in an aqueous reaction system. It thereby overcomes the limitation of by‐product formation that severely limits the current fermentative process. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 74: 317–325, 2001.