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Tadashi Sato

Bio: Tadashi Sato is an academic researcher. The author has contributed to research in topics: Fumaric acid & Ammonium fumarate. The author has an hindex of 25, co-authored 75 publications receiving 2074 citations.


Papers
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TL;DR: The immobilization of asparatase-containing Escherichia coli was investigated by various methods, and the most active immobilized cells were obtained by entrapment in a polyacrylamide gel lattice.
Abstract: The immobilization of asparatase-containing Escherichia coli was investigated by various methods, and the most active immobilized cells were obtained by entrapment in a polyacrylamide gel lattice. Other asparatase-containing bacteria were also entrapped by the same method, and the enzymatically active immobilized cells were obtained. The aspartase activity of the immobilized E. coli cells was increased nine- to tenfold by autolysis of the cells entrapped in the gel lattice. Enzymatic properties of the immobilized E. coli cells were investigated and compared with those of the intact cells. The optimal pH was 8.5 for the immobilized cells and 10.5 for the intact cells. The aspartase activities of immobilized and intact cells were not activated by Mn(2+), which can activate the immobilized and native aspartases. The heat stability of the immobilized cells was somewhat higher than that of the intact cells. Bivalent metal ions such as Mn(2+), Mg(2+), Ca(2+) protected against thermal inactivation of the aspartase activity of the immobilized and intact cells.

233 citations

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TL;DR: Conditions for the gelation of k ‐carrageenan, which is a new polymer for immobilization of enzymes and microbial cells, were investigated in detail and immobilized preparations were easily tailor‐made to various shapes such as cube, bead, and membrane.
Abstract: Conditions for the gelation k-carrageenan, which is a new polymer for immobilization of enzymes and microbial cells, were investigated in detail k-Carrageenan was easily induced to gel by contact with metal ions, amines, amino acid derivatives, and water-miscible organic solvents By using this property of k-carrageenan, the immobilization of enzymes and microbial cells was investigated Several kinds of enzymes and microbial cells were easily immobilized with high enzyme activities Immobilized preparations were easily tailor-made to various shape such as cube, bead, and membrane The obtained immobilized preparations were stable, and columns packed with them were used for continuous enzyme reaction for a long period Their operational stabilities were enhanced by hardening with glutaraldehyde and hexamethylenediamine

154 citations

Journal ArticleDOI
TL;DR: Conditions for continuous production of L-aspartic acid from ammonium fumarate were investigated using a column packed with immobilized Escherichia coli cells entrapped in a polyacrylamide gel lattice and the immobilized cell column was very stable.
Abstract: By using a column packed with immobilized Escherichia coli cells entrapped in a polyacrylamide gel lattice, conditions for continuous production of L-aspartic acid from ammonium fumarate were investigated. When a solution of 1 M ammonium fumarate (pH 8.5) containing 1 mM Mg(2+) was passed through the immobilized cell column at a flow rate of space velocity (SV) = 0.8 at 37 C, the highest rate of reaction was attained. From the column effluents, L-aspartic acid was obtained in good yield. The immobilized cell column was very stable.

116 citations

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TL;DR: The microbial cells of Pseudomonas putida ATCC 4359 were immobilized by entrapment in a polyacrylamide gel lattice and the permeability of substrate or product through the cell wall und the heat stability of the enzyme were increased by immobilization of the cells.
Abstract: The microbial cells of Pseudomonas putida ATCC 4359 were immobilized by entrapment in a polyacrylamide gel lattice. Enzymatic properties of L‐arginine deiminase of the immobilized P. putida cells were investigated and compared with those of the intact cells. The permeability of substrate or product through the cell wall und the heat stability of the enzyme were increased by immobilization of the cells. No difference was observed between pH activity curves of the intact and immobilized cells. The optimal temperature for the formation of L‐citrulline was 37°C for the intact cells and 55° C for the immobilized cells.

98 citations


Cited by
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TL;DR: In all cases, enzyme engineering via immobilization techniques is perfectly compatible with other chemical or biological approaches to improve enzyme functions and the final success depend on the availability of a wide battery of immobilization protocols.

3,016 citations

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TL;DR: Three-dimensional structures of bacterial lipases were solved to understand the catalytic mechanism of lipase reactions and will enable researchers to tailor new lipases for biotechnological applications.
Abstract: ▪ Abstract Bacteria produce and secrete lipases, which can catalyze both the hydrolysis and the synthesis of long-chain acylglycerols. These reactions usually proceed with high regioselectivity and enantioselectivity, and, therefore, lipases have become very important stereoselective biocatalysts used in organic chemistry. High-level production of these biocatalysts requires the understanding of the mechanisms underlying gene expression, folding, and secretion. Transcription of lipase genes may be regulated by quorum sensing and two-component systems; secretion can proceed either via the Sec-dependent general secretory pathway or via ABC transporters. In addition, some lipases need folding catalysts such as the lipase-specific foldases and disulfide-bond–forming proteins to achieve a secretion-competent conformation. Three-dimensional structures of bacterial lipases were solved to understand the catalytic mechanism of lipase reactions. Structural characteristics include an α/β hydrolase fold, a catalytic ...

1,072 citations

Journal ArticleDOI
TL;DR: The development and attributes of several established and emerging industrial applications for immobilized enzymes, including high-fructose corn syrup production, pectin hydrolysis, debittering of fruit juices, interesterification of food fats and oils, biodiesel production, and carbon dioxide capture are reviewed herein, highlighting factors that define the advantages of enzyme immobilization.
Abstract: Although many methods for enzyme immobilization have been described in patents and publications, relatively few processes employing immobilized enzymes have been successfully commercialized. The cost of most industrial enzymes is often only a minor component in overall process economics, and in these instances, the additional costs associated with enzyme immobilization are often not justified. More commonly the benefit realized from enzyme immobilization relates to the process advantages that an immobilized catalyst offers, for example, enabling continuous production, improved stability and the absence of the biocatalyst in the product stream. The development and attributes of several established and emerging industrial applications for immobilized enzymes, including high-fructose corn syrup production, pectin hydrolysis, debittering of fruit juices, interesterification of food fats and oils, biodiesel production, and carbon dioxide capture are reviewed herein, highlighting factors that define the advantages of enzyme immobilization.

978 citations

Journal ArticleDOI
TL;DR: The main polysaccharides currently used in the biomedical and pharmaceutical domains are chitin and its derivative chitosan, hyaluronan, and alginates.
Abstract: This review concerns the applications of some polysaccharides in the domain of biomaterials and bioactive polymers. Natural polysaccharides from different sources have been studied for a long time, and their main properties are summarized in this paper; some of their derivatives obtained by chemical modification are also described. The main polysaccharides currently used in the biomedical and pharmaceutical domains are chitin and its derivative chitosan, hyaluronan and alginates. Alginates are well known for their property of forming a physical gel in the presence of divalent counterions (Ca, Ba, Sr) whereas carrageenans form a thermoreversible gel; these seaweed polysaccharides are mainly used to encapsulate different materials (cells, bacteria, fungi). Other promising systems are the electrostatic complexes formed when an anionic polysaccharide is mixed with a cationic polysaccharide (e.g. alginate/chitosan or hyaluronan/chitosan). An important development of the applications of polysaccharides can be predicted for the next few years in relation to their intrinsic properties such as biocompatibility and biodegradability in the human body for some of them; they are also renewable and have interesting physical properties (film-forming, gelling and thickening properties). In addition, they are easily processed in different forms such as beads, films, capsules and fibres. Copyright © 2007 Society of Chemical Industry

866 citations

Journal ArticleDOI
TL;DR: This review evaluates the merits and limitations of the two common encapsulation techniques, namely extrusion and emulsion, to encapsulate the probiotics for their use in the fermented and other dairy products.

775 citations