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At least 19 recordsLinked to original sources
PubMed1978

[Nisin formation by immobilized cells of the lactic acid bacterium, Streptococcus lactis].

The problem of microbial cell immobilization at present attracts the ever increasing attention of the scientists, since such organisms may be the source of various enzymes. Production of nizin by the immobilized cells of Str. lactis was studied. It was found that the cells of Str. lactis incorporated into polyacrylamide gel produced nizit on definite media. Still, the amount of the antibiotic was 2-3 times lower than in case of using free cells. The effect of a number of factors on the process of immobilization was studied and the influence of some factors, such as temperature, pH, aeration on nizin synthesis by the immobilized cells of the streptococcus was elucidated. Optimal conditions for nizin biosynthesis by the immobilized cells of Str. lactis were developed.

Acrylamides↗
PubMedDate not supplied

[Lipolytic activity of Mycobacterium rubrum cells, immobilized in polyacrylamide gel].

The cells of Mycobacterium rubrum 403 possessing lipolytic activity can be immobilized in polyacrylamide gel. The lipolytic activity of immobilized cells is 20-30 per cent of the activity of free cells. The lipolytic activity of immobilized cells does not changee after they have been used once and then stored at +4 degrees C during 5 months. If immobilized cells have been used several times, their lipolytic activity does not change during 1.5 months. In the case of immobilized cells, the temperature optimum is broader, pH is more alkaline, and the inhibiting action of Mg and Cu ions decreases.

Bacteriological Techniques↗
PubMedDate not supplied

[Study on L-malic acid catabolism by "Lactobacillus casei" cells immobilized into polyacrylamide gel lattice (author's transl)].

Study on L-malic acid catabolism by Lactobacillus casei cells immobilized into polyacrylamide gel lattice has shown that the pH profil of malic acid decarboxylase activity does not differ significantly from that of free cells. The apparent enzymatic constant value as determined by the Warburg manometric method is 5 X 10(-3) M for free cells and 1.25 X 10(-2) M for immobilized cells. Malic acid decarboxylase activity can be preserved in immobilized cells over a 12 month period when the reaction vessel is fed continuously with the growth medium. It is noteworthy that the reaction vessel is similar to a constant activity reactor whose apparent enzymatic constant value, of 6,25 X 10(-3) M, does not differ significantly from that of free cells. Labelling of the cells with 14C-glycin has shown that the immobilized cells released 14 per cent of the radioactivity over a 65 hour period, indicating that the cells are possibly in a non proliferating state. After 9 months of working, a large fraction of viable bacterial cells can be isolated again. The use of such a reactor for producing metabolites is proposed.

Acrylamides↗
PubMed1979

Bacitracin production by whole cells immobilized in polyacrylamide gel.

Whole cells of Bacillus sp., bacitracin-producing bacteria, were immobilized in polyacrylamide gel prepared by using 5% total acrylamide (95% acrylamide monomer and 5% N, N'-methylenebis acrylamide). Bacitracin production by the immobilized whole cells was examined by using various fermentation media. In starch-bouillon medium, the initial activity of immobilized whole cells for bacitracin production was 20 to 25% that of an equivalent amount of washed cells. With successive utilizations in 1% peptone as reaction medium, activity of the immobilized whole cells increased gradually and reached a steady-state maximum having a value of 80 to 90% of the activity obtained initially with washed cells, whereas the washed cells lost most activity when utilized successively. What appeared to be growth of the bacteria in the gel was observed by electron microscopy. Therefore, the activation of immobilized whole cells during successive utilizations apparently resulted from the growth of whole cells in the gel, especially at the gel surface.

Acrylamides↗
PubMed1979

Mass-transfer effects on the rate of isomerization of D-glucose into D-fructose, catalyzed by whole-cell immobilized glucose isomerase.

The investigated catalyst system consists of immobilized Arthrobacter cells containing the enzyme glucose isomerase, which catalyzes the isomerization of glucose into fructose. The internal structure of the catalyst was determined from electrom microscope photographs of replicas of freeze-etched catalyst. On the basis of the photographs a model for the internal structure of the catalyst was proposed. This structure was subsequently used to describe the reaction including mass-transfer effects. It appeared that under normal operating conditions the external mass-transfer rate does not influence the overall rate of reaction. The effect of internal mass-transfer resistances on the overall reaction rate can well be accounted for by the so-called porous sphere model. The intrinsic kinetics of the isomerization catalyzed by the present catalyst system can be represented by a modified Michaelis-Menten equation for a reversible one-substrate reaction.

Arthrobacter↗
PubMedDate not supplied

[Catalytic properties of immobilized cells of methane-oxidizing bacteria].

The article deals with conditions for immobilization of methane-oxidizing bacteria cells as well as with catalytic properties of the immobilized cells. The method of immobilization in polyacrylamide gel is shown to be not suitable for cells of methane-oxidizing bacteria. The greatest number of cells (85%) is immobilized on sylochrome modified by cyanuric chloride. However, the catalytic properties of the methane-oxidizing bacteria are better retained when the bacteria are immobilized on sylochrome modified by isocyanate. A stand installation is created for studying the catalytic properties of the immobilized cells oxidizing substrates in the gas phase.

Acrylamides↗
PubMed1979

[Kinetics of the aspartate-aminotransferase reaction catalyzed by free and immobilized cells of E. coli].

The kinetics of the aspartate-aminotransferase reaction were studied, using free and immobilized cells of E. coli, strain 85 as an enzyme source. It was shown that the reaction is limited by mass transport of the reagents through the bacterial cell membrane even at high concentrations of the substrates in the surrounding solution. The polyacrylamide gel-incorporated cells of E. coli, strain 85 catalyze the aspartate-aminotransferase reaction more effectively as compared to free or destroyed cells. In the latter case the reaction is characterized by the following kinetic parameters: the effective values of the stationary rate of the product accumulation and its stationary efflux from the cell are equal to (15,37 +/- 0.4) . 10(-6) mole/s/mg of protein and (3,01 +/- 0,8) . 10(-20) mole/s per 1 cell. respectively. The steady-state constant for glutamate synthesis from aspartic acid is equal to 0,22--0,23.

Aspartate Aminotransferases↗
PubMed1979

[Dependence of the rate of aspartate ammonia-lyase reaction catalyzed by free and immobilized cells of E. coli on temperature and preliminary thermal treatment].

The effects of temperature (45--55 degrees) and duration of thermal treatment on the L-aspartase activity of free and immobilized on polyacrylamide gel cells of E. coli, strain 85 were studied. It was found that preliminary thermal treatment of the cells at 50 degrees for 40--60 min is optimal for a high aspartase activity. Within the temperature interval of 20--55 degrees the temperature dependence of effective rate constants of L-aspartate synthesis obeys the Arrhenius equation, whereas the effective energy of activation is decreased from 12,6 to 3,6 kcal/mole, when the "activation" of the cells shows an increase.

Ammonia-Lyases↗
PubMed1978

A new method for cell immobilization.

A new method for producing particles and membranes containing immobilized bacteria is presented. These immobilized bacteria display good stability over time making them well suited for use in a packed-bed reactor. Such a reactor is tested as a function of the different parameters of the system. The results are qualitatively similar to those obtained with purified enzyme reactors, but some discrepancies with the plug-flow model are noted. It is necessary to use a more sophisticated model in order to fit the experimental data.

Bacteriological Techniques↗
PubMedDate not supplied

Nature of transformation of hydrocortisone by cells incorporated into polyacrylamide gel.

The ability of Mycobacterium globiforme 193 cells immobilized in polyacrylamide gel (Paag) to transform soluble and microcrystalline hydrocortisone was investigated under conditions to periodic aeration. It was found that the specific 3-oxosteroid-delta'-dehydrogenase activity of immobilized cells hardly differs from that of free cells and averages 0.06 mumole/mg cells . min; the quantitative and qualitative composition of the transformation products formed by free and immobilized cells was identical. The linear relation between the accumulation of the reaction product, prednisolone, and the transformation time, the absence of an activating effect of SAA [surface-active agents] on the 3-oxosteroid-delta'-dehydrogenase activity, the correlation between enzymatic activity and viability, and the absence of an increase in activity during repeated transformations indicate that the cytoplasmic membrane of Myc. globiforme is not a significant diffusion barrier for the reaction substrate and product. Maintenance of immobilized cells in a viable state is a necessary condition of the retention of enzymatic activity by these cells. "Activation" of immobilized cells is achieved by incubating the granules in nutrient medium. The cause of the "activation," in our opinion, is the appearance of a new surface and, probably, internal cell population.

3-Hydroxysteroid Dehydrogenases↗
PubMed2026

Nitrilase-mediated degradation of insecticides flonicamid and thiacloprid by immobilized engineered Escherichia coli with a novel pathway.

The nitrile‑containing insecticides flonicamid (FLO) and thiacloprid (THI) are widely used in agriculture, posing risks to the environment and animal health. Nitrilase is a key catalyst for the degradation of nitrile compounds, and immobilized engineered bacteria are preferred in wastewater treatment. However, immobilized engineered bacteria expressing nitrilase have never been investigated for pollutant degradation. Here, engineered Escherichia coli pET28a‑VbNitA harboring the nitrilase gene VbNitA was immobilized by calcium alginate encapsulation. FLO was degraded into N-(4-trifluoromethylnicotinoyl)glycinamide and 4-(trifluoromethyl)nicotinol glycine by the immobilized cells via VbNitA. THI was converted to THI‑amide and THI‑imine using the same system. Notably, this is the first report of a nitrilase converting THI to THI‑amide and of THI‑imine as a biodegradation intermediate. Compared with free cells, the immobilized E. coli pET28a‑VbNitA showed higher tolerance to high temperature, alkaline, and acidic environments, and better long-term storage stability. The substrate inhibition model showed that the optimal initial concentrations of FLO and THI for degradation by immobilized E. coli pET28a‑VbNitA were 45.13 and 127.50 μmol/L, respectively. FLO was degraded more rapidly than THI by the immobilized cells. Molecular docking revealed that both FLO and THI formed stable interactions with VbNitA, with FLO positioned closer to Cys165 of the catalytic triad. This study presents a novel THI degradation pathway and provides a new, efficient immobilized biocatalyst for the remediation of wastewater with nitrile‑containing insecticides.

Escherichia coli↗
PubMed1979

Immobilization of Streptomyces phaerochromogenes by radiation-induced polymerization of glass-forming monomers.

Immobilization of Streptomyces phaerochromogenes was studied by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperatures. Radiation damage of the enzyme could be avoided by choosing irradiation at low temperatures. The enzymatic activity of immobilized cells increased remarkably with a decrease in the irradiation temperature of about -24 degrees C. In constrast to the case of cell-free enzyme immobilization, the most characteristic case was than in these immobilized cells, the enzymatic activity did not decrease with repeated use even in the composite obtained at much lower monomer concentrations. Another characteristic of immobilized cells was the increase in enzymatic activity in the initial stage of repeated use, which could be attributed to the swelling effect of the polymer matrix, thereby increasing the enzymatic activity of whole cells.

Adsorption↗
PubMed1978

Continuous dehydrogenation of a steroid with immobilized microbial cells: effect of an exogenous electron acceptor.

Whole cells of Pseudomonas testosteroni, induced to synthesize steroid-transforming enzymes beforehand, have been immobilized by entrapment in polyacrylamide gel. The immobilized cells have been used to catalyze the continuous delta1-dehydrogenation of Reichstein's substance S under various conditions in the presence of phenazine methosulfate (PMS), an electron acceptor for the cell-free delta1-dehydrogenase. The presence of PMS substantially increases the rate of reaction when fed with the steroid substrate to a continuous stirred tank reactor containing the immobilized cells. The operational half-life of the delta1-dehydrogenase activity of the cells, about 103 hr under the best operating conditions, is essentially unaffected by the presence of PMS. Though the acceleration of the reaction may be due to PMS-mediated passage of electrons from some component in the electron transport chain to molecular oxygen, the lack of a similar effect with methylene blue is consistent with the conclusion that PMS functions directly as the electron acceptor for the delta1-dehydrogenase.

17-Hydroxycorticosteroids↗
PubMed1979

Microbiological transformations. XI. The use of immobilized Rhodotorula mucilaginosa cells to reduce some ketones.

Rhodotorula mucilaginosa cells were immobilized by polymerizing acrylamide with the addition of a cross-linked agent, a catalyst and an initiator. This gel was used for the stereospecific reduction of acetophenone and alpha-acetylnaphthalene resulting chromatographically pure alcohols with absolute configuration S. When karen-3-dion-2,5 was used as substrate, four products were obtained. Androstenolone was reduced with 30% yield. Activity of the immobilized cells could be regenerated by glucose.

Acetophenones↗
PubMed1979

Penicillin G production by immobilized whole cells of Penicillium chrysogenum.

Penicillium chrysogenum was immobilized in polyacrylamide gel prepared from 5% acrylamide monomers (85% acrylamide and 15% N,N'-methylene bisacrylamide). Penicillin produced from glucose by the immobilized mycelium was 17% of that produced by washed mycelium. However, the activity of penicillin production of the washed mycelium decreased with repeated use. On the other hand, the activity of the immobilized mycelium increased initially and decreased gradually with repeated use. The rate of oxygen uptake of the immobilized mycelium was about 30% of that of the washed mycelium. The immobilized mycelium required oxygen for the production of penicillin.

2-Aminoadipic Acid↗