Pham Huynh Ninh(a), Kohsuke Honda(a,b), Yukako Yokohigashi(a), Kenji Okano(a),Takeshi Omasa(a,c),Hisao Ohtake(a)

Department of Biotechnology, Graduate School of Engineering, Osaka University, Osaka, Japan (a); PRESTO, Japan Science and Technology Agency (JST), Saitama, Japan(b);Department of Life System, Institute of Technology and Science, The University of Tokushima, Tokushima, Japan(c)

Abstract

The heat treatment of recombinantmesophilic cells having heterologous thermophilic enzymes results in the denaturation of indigenousmesophilic enzymes and the elimination of undesired side reactions; therefore, highly selective whole-cell catalysts comparable to purified enzymes can be readily prepared. However, the thermolysis of host cells leads to the heat-induced leakage of thermophilic enzymes, which are produced as soluble proteins, limiting the exploitation of their excellent stability in repeated and continuous reactions. In this study, Escherichia coli cells having the thermophilic fumarase from Thermus thermophilus (TtFTA) were treated with glutaraldehyde to prevent the heat-induced leakage of the enzyme, and the resulting cells were used as a whole-cell catalyst in repeated and continuous reactions. Interestingly, although electronmicroscopic observations revealed that the cellular structure of glutaraldehyde-treated E. coli was not apparently changed by the heat treatment, themembrane permeability of the heated cells to relatively smallmolecules (up to at least 3 kDa) was significantly improved. By applying the glutaraldehyde-treated E. coli having TtFTA to a continuous reactor equipped with a cell-separationmembrane filter, the enzy-matic hydration of fumarate tomalate could be operated formore than 600min with amolar conversion yield of 60%or higher.

Published Ahead of Print 18 January 2013.

10.1128/AEM.03752-12.

2013, 79(6):1996. DOI: Appl. Environ. Microbiol.

Kenji Okano, Takeshi Omasa and Hisao Ohtake

Pham Huynh Ninh, Kohsuke Honda, Yukako Yokohigashi,