Tetsuya Tosa

Bio: Tetsuya Tosa is an academic researcher from University of Pennsylvania. The author has contributed to research in topics: Immobilized enzyme & Fumaric acid. The author has an hindex of 40, co-authored 162 publications receiving 4630 citations.

Immobilized Aspartase-Containing Microbial Cells: Preparation and Enzymatic Properties

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.

Biochemical Bases for the Antimetabolite Action of l-Serine Hydroxamate

Abstract: The amino acid analogue l-serine hydroxamate, which is bacteriostatic for Escherichia coli, has been shown to inhibit protein synthesis. The antimetabolite is a competitive inhibitor of seryl-transfer ribonucleic acid (tRNA) synthetase with a K(i) value of 30 mum. Mutants resistant to l-serine hydroxamate have been selected, and three were shown to have seryl-tRNA synthetases with increased K(i) values. One mutant contains a 3-phosphoglycerate dehydrogenase which is insensitive to inhibition by l-serine.

Immobilization of enzymes and microbial cells using carrageenan as matrix.

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

Basic Studies for Continuous Production of L-Aspartic Acid by Immobilized Escherichia coli Cells

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.

A review on phytoremediation of heavy metals and utilization of its byproducts.

Abstract: This review presents the status of phytoremediation technologies with particular emphasis on phytoextraction of soil heavy metal contamination. Unlike organic compounds, metals cannot be degraded, and cleanup usually requires their removal. Most of the conventional remedial technologies are expensive and inhibit the soil fertility; this subsequently causes negative impacts on the ecosystem. Phytoremediation is a cost effective, environmental friendly, aesthetically pleasing approach most suitable for developing countries. Despite this potential, phytoremediation is yet to become a commercially available technology in India. This paper reports about the mobility, bioavaliability and plant response to presence of soil heavy metals. It classifies the plants according to phytoextraction mechanism and discusses the pathway of metal in plants. Various techniques to enhance phytoextraction and utilization of by-products have been elaborated. Since lot of biomass is produced during this process, it needs proper disposal and management. It also gives an insight into the work done by authors, which focuses on high biomass extractor plants. High biomas weeds were selected to restrict the passage of contaminants into the food chain by selecting non-edible, disease resistant and tolerant plants, which can provide renewable energy. Thus making phytoextraction more viable for present utilization. Keywords. heavy metals, phytoextraction, hyperaccumulator, indicator, excluder species

Bacterial lipases: an overview of production, purification and biochemical properties.

Abstract: Lipases, triacylglycerol hydrolases, are an important group of biotechnologically relevant enzymes and they find immense applications in food, dairy, detergent and pharmaceutical industries. Lipases are by and large produced from microbes and specifically bacterial lipases play a vital role in commercial ventures. Some important lipase-producing bacterial genera include Bacillus, Pseudomonas and Burkholderia. Lipases are generally produced on lipidic carbon, such as oils, fatty acids, glycerol or tweens in the presence of an organic nitrogen source. Bacterial lipases are mostly extracellular and are produced by submerged fermentation. The enzyme is most commonly purified by hydrophobic interaction chromatography, in addition to some modern approaches such as reverse micellar and aqueous two-phase systems. Most lipases can act in a wide range of pH and temperature, though alkaline bacterial lipases are more common. Lipases are serine hydrolases and have high stability in organic solvents. Besides these, some lipases exhibit chemo-, regio- and enantioselectivity. The latest trend in lipase research is the development of novel and improved lipases through molecular approaches such as directed evolution and exploring natural communities by the metagenomic approach.

Industrial use of immobilized enzymes

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.