Studies on the continuous production of (R)-(−)-phenylacetylcarbinol in an enzyme-membrane reactor |
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Authors: | Peter Iwan Gü nter Goetz Susanne Schmitz Bernhard Hauer Michael Breuer Martina Pohl |
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Affiliation: | a Institut für Enzymtechnologie der Universität Düsseldorf im Forschungszentrum Jülich, D-52426 Julich, Germany b BASF AG, D-67056 Ludwigshafen, Germany |
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Abstract: | The optimization of a continuous enzymatic reaction yielding (R)-(−)-phenylacetylcarbinol ((R)-PAC), a key intermediate of the (1R,2S)-(−)-ephedrine synthesis, is presented. We compare the suitability of different mutants of the pyruvate decarboxylase (PDC) from Zymomonas mobilis with respect to their application in biotransformation using pyruvate or acetaldehyde and benzaldehyde as substrates, respectively. Starting from 90 mM pyruvate and 30 mM benzaldehyde, (R)-PAC was obtained with a space time yield of 27.4 g/(L·day) using purified PDCW392I in an enzyme-membrane reactor. Due to the high stability of the mutant enzymes PDCW392I and PDCW392M towards acetaldehyde, a continuous procedure using acetaldehyde instead of pyruvate was developed. The kinetic results of the enzymatic synthesis starting from acetaldehyde and benzaldehyde demonstrate that the carboligation to (R)-PAC is most efficiently performed using a continuous reaction system and feeding both aldehydes in equimolar concentration. Starting from an inlet concentration of 50 mM of both aldehydes, (R)-PAC was obtained with a space-time yield of 81 g/(L·day) using the mutant enzyme PDCW392M. The new reaction strategy allows the enzymatic synthesis of (R)-PAC from cheap substrates free of unwanted by-products with potent mutants of PDC from Z. mobilis in an aqueous reaction system. |
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Keywords: | (R)-(−)-phenylacetylcarbinol Enzyme–membrane reactor Biotransformation Pyruvate decarboxylase Site-directed mutagenesis |
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