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An Activity, Stability and Selectivity Comparison of Propioin Synthesis by Thiamine Diphosphate‐Dependent Enzymes in a Solid/Gas Bioreactor
Author(s) -
Mikolajek Renaud,
Spiess Antje C.,
Pohl Martina,
Lamare Sylvain,
Büchs Jochen
Publication year - 2007
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.200700095
Subject(s) - pseudomonas fluorescens , chemistry , pseudomonas putida , substrate (aquarium) , bioreactor , enzyme , cofactor , thiamine , biocatalysis , transketolase , biochemistry , chromatography , organic chemistry , catalysis , bacteria , reaction mechanism , biology , ecology , genetics
Enzymatic carboligation in a solid/gas bioreactor represents a new challenge in biotechnology. In this paper, the continuous gas‐phase production of propioin from two propanal molecules by using thiamine diphosphate‐dependent enzymes was studied. Two enzymes were used, namely benzaldehyde lyase (BAL) from Pseudomonas fluorescens and benzoylformate decarboxylase (BFD) from Pseudomonas putida . The enzymes are homologous and catalyze carboligase and carbolyase reactions in which no external cofactor regeneration is needed. The influence of water and substrate activity on the initial reaction rate and biocatalyst stability was investigated. An increase in water activity raised the initial reaction rates to the maximal values of 250 and 80 U g −1 for BAL and BFD, respectively. The half‐life showed the same trend with maximal values of 50 and 78 min for BAL and BFD, respectively. The increase in the half‐life by increasing water activity was unexpected. It was also observed that BFD is more stable than BAL in the presence of the substrate propanal. Both enzymes showed substrate inhibition in the kinetic studies, and BAL was also deactivated during the reaction. Unexpectedly, the stereoselectivity of both enzymes ( ee of 19 % for BAL and racemic mixture for BFD) was significantly impaired in the gas phase compared to the liquid phase.