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Modeling and kinetic analysis of the reaction system using whole cells with separately and co‐expressed D ‐hydantoinase and N ‐carbamoylase
Author(s) -
Park JooHo,
Oh KiHoon,
Lee DongCheol,
Kim HakSung
Publication year - 2002
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.10259
Subject(s) - chemistry , substrate (aquarium) , racemization , hydantoin , enzyme , reaction rate , biocatalysis , enzyme kinetics , kinetics , stereochemistry , product inhibition , chromatography , non competitive inhibition , reaction mechanism , biochemistry , catalysis , active site , biology , quantum mechanics , ecology , physics
We developed a kinetic model that describes a heterogeneous reaction system for the production of D ‐ p ‐hydroxyphenylglycine from D , L ‐ p ‐hydroxyphenyl‐hydantoin using D ‐hydantoinase of Bacillus stearothermophilus SD1 and N ‐carbamoylase of Agrobacterium tumefaciens NRRL B11291. As a biocatalyst, whole cells with separately or co‐expressed enzymes were used. The reaction system involves dissolution of substrate particles, enzymatic conversion, racemization of the L ‐form substrate, and transfer of the dissolved substrate, intermediate, and product through the cell membrane. Because the two enzymes have different pH optimum, kinetic parameters were evaluated at different pH for the reaction systems. The model was simulated using the kinetic parameters and compared with experimental data, and it was found that the kinetic model well describes the behavior of the reaction systems using whole cells with separately and co‐expressed enzymes. Factors affecting the kinetics of the reaction systems were analyzed on the basis of the kinetic model. In the reaction system with separately expressed enzymes, racemization rate and transport of the reaction intermediate ( N ‐carbamoyl‐ D ‐ p ‐hydroxyphenylglycine) were revealed to be the limiting factors at neutral pH, resulting in accumulation of intermediate in the reaction medium. At alkaline condition, on the other hand, inhibition of N ‐carbamoylase by ammonia was severe, and thereby the reaction rate significantly reduced. In the co‐expressed enzyme system, accumulation of intermediate was negligible in the reaction medium, and the improved performance was observed compared to that with separately expressed enzymes. The present model might be applied for the optimization and development of the reaction system using two sequential enzymes. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 779–793, 2002.