[Aspartase activity and the stability of Escherichia coli cells immobilized in different carrageenan samples]. / Aspartaznaia aktivnost' i stabil'nost' kletok Escherichia coli, immobilizovannykh v razlichnye obraztsy karraginana.

The cells of Escherichia coli 85 immobilized in carrageenan from various sources were being studied for the aspartase activity and stability. These properties of the resultant preparations which display a relatively high and stable biocatalytic activity were shown to be almost independent of the raw material from which carrageenan was obtained and of the degree of its purification.

[Comparison of the aspartase activity and its stability in Escherichia coli cells immobilized on polyacrylamide gel and carrageenan]. / Sravnenie aspartaznoi aktivinosti i ee stabil'nosti u kletok Escherichia coli, immobilizovannykh v poliakrilamidnyi gel' i karraginan.

The conditions for immobilization of Escherichia coli cells (Soviet strain 85) on the natural polysaccharide carrier carrageenan (Soviet-made) were investigated and kinetic regularities of the aspartase reaction catalysed by immobilized in carrageenan cells of E. coli 85 were established. The conditions for retaining a high aspartase activity and stability of biocatalysts based on the E. coli 85 cells immobilized in PAAG and carrageenan were determined using full-loaded tanks for continuous synthesis of L-aspartic acid. The time-stable aspartase activity of the biocatalyst can be increased by treating the beads of the catalyst with bifunctional reagents (hexamethylenediamine, glutaraldehyde), the most active catalyst for the biotechnological synthesis of L-aspartic acid being obtained when carrageenan is used.

[Stability of the biocatalysts of L-aspartic acid synthesis based on immobilized Escherichia coli cells]. / Stabil'nost' biokatalizatorov sinteza L-asparaginovoi kisloty na osnove immobilizovannykh kletok Escherichia coli.

Experiments were carried out to investigate the process of a continuous enzymatic synthesis of L-aspartic acid from ammonium fumarate in uniform filling flow reactors. Escherichia coli (Soviet strain 85) cells immobilized in polyacrylamide gel granules reinforced by a solid carrier were used as biocatalysts. The conditions, under which a high aspartase activity of the biocatalyst and a stable hydrodynamic performance of the reactor were maintained, were determined. The main kinetic characteristics of a continuous performance of the reactor for 150 days were obtained.

[Kinetics mechanism of L-aspartate synthesis from ammonium fumarate catalyzed by free and immobilized cells of E. coli]. / Kineticheskii mekhanizm reaktsii sinteza L-asparaginovoi kisloty iz fumarata ammoniia, kataliziruemoi svobodnymi i immobilizovannymi kletkami Escherichia coli.

A detailed study of kinetic peculiarities of the L-aspartate-ammonium-lyase reaction catalyzed by free and immobilized E. coli 85 cells incorporated into polyacrylamide gel, has been carried out. The effects of different types of bacterial cell "activation", substrate concentration and temperature on the reaction rate have been investigated. It was shown that the rate of the reaction is limited by the rate of the substrate transfer through the cell and cytoplasmic membranes and at sufficiently high values of the substrate can be described in terms of zero-order kinetics with respect to substrate and reaction products concentrations A kinetic model based on the diffuse and transfer processes of translocation of the aspartate-ammonium-lyase reaction participants through the cell and cytoplasmic membranes is proposed.