Coimmobilization of D-amino acid oxidase and catalase by entrapment ofTrigonopsis variabilis in radiation polymerised Polyacrylamide beads

Trigonopsis variabilis induced for D-amino acid oxidase and catalase was immobilized by entrapment in Polyacrylamide beads obtained by radiation polymerisation. Permeabilization of the cells was found to be essential for optimal activity of the enzymes in free cells. However, the process of entrapment itself was found to eliminate the permeability barrier of cells immobilized in Polyacrylamide. The two enzymes exhibited a differential response on Polyacrylamide entrapment. Thus, D-amino acid oxidase activity was stabilized to heat inactivation whereas catalase in the same cells showed a destabilization on entrapment in Polyacrylamide. The coimmobilized enzyme preparation showed an operational half life of 7–9 days after which the D-amino acid oxidase activity remained stable at a value 35–40% of that of the initial activity for a study period of 3 weeks. Coimmobilization of MnO₂ was not effective in enhancing the operational life of the enzyme preparation.     

Entrapment of microbial cells and organelles with hydrophilic urethane prepolymers

Summary Microbial cells and cellular organelles were immobilized by mixing aqueous suspensions of the biocatalysts with water-miscible urethane prepolymers. Thus immobilized preparations of acetone-dried cells of Arthrobacter simplex and thawed cells of Nocardia rhodocrous showed appreciable {ie351-1} activities in the transformation of hydrocortisone into prednisolone and 4-androstene-3,17-dione to androst-1,4-diene-3,17-dione, respectively. The activities of catalase and alcohol oxidase were observed in the immobilized peroxisomes (microbodies) of a methanol-grown yeast Kloeckera sp. No. 2201. Yeast mitochondria entrapped with the prepolymer showed adenylate kinase activity. These results indicate the usefulness of the urethane prepolymers as convenient materials for entrapment of not only enzymes, but also organelles and microbial cells.     

Entrapment of a Trigonopsis variabilis D‐amino acid oxidase variant F54Y for oxidative deamination of cephalosporin C

Trigonopsis variabilis D ‐amino acid oxidase (TvDAAO) is an enzyme used in the industrial bioconversion of cephalosporin C (CPC) into 7‐aminocephalosporanic acid, a crucial biosynthetic nucleus for a wide spectrum of semi‐synthetic cephem antibiotics. Using homology modeling and site‐directed mutagenesis, we have previously shown that the TvDAAO variant F54Y possesses improved catalytic activity and thermostability. To further explore its industrial application, the conditions for immobilization of the enzyme were examined in the present investigation. The results showed that entrapment in a calcium alginate (Ca‐alginate) matrix using 2% alginate, 500 mM CaCl₂, and 15 min stabilization appeared to be optimal for the immobilization of F54Y. The entrapped enzyme allowed complete CPC conversion. The entrapped enzyme also showed good operational stability and retained at least 90% of its original activity after 20 reaction cycles. To conclude, the entrapment of F54Y in Ca‐alginate appeared to be a simple and efficient biocatalysis system with potential application in the antibiotics industry.     

Ethanol production by Zymomonas mobilis entrapped in alumina pellets

Summary Zymomonas mobilis cells were immobilized on pellets of alumina (Al₂O₃) by entrapment based on electrostatic forces. Entrapped cells produced 52 g/l^-1 ethanol every 24 h for many successive fermentation batches, when inoculated in batch synthetic media containing 12% glucose. It was shown that the rate of growth, ethanol production and glucose utilization increased when Al₂O₃ was added in the growth medium. This increase was dependent upon the concentration of Al₂O₃. The optimum conditions for immobilization of Z. mobilis on Al₂O₃ were established. Reduction in productivity and yield was not observed for up to 15 successive fermentation batches using the same entrapped cells.     

Prevention of limiting substrate diffusion in an immobilized enzyme reaction system: Lectin-induced activation of gel-entrapped β-D-galactosidase

Summary Escherichia coli -D-galactosidase (EC 3.2.1.23) was entrapped in polyion complex-stabilized alginate gel beads together with a lectin fromRicinus communis (RCA₁ lectin). The rate of entrapped enzyme-catalyzed hydrolysis of O-nitrophenyl--D-galactoside dramatically increased with an increase in lectin content, and at the maximum level of lection content the entrapped enzyme activity exceeded the native enzyme activity. A rapid decrease in the apparent K_m was observed while increasing the lectin content, whereas the V_max value varied insignificantly.     

Entrapment of purified novel dextransucrase obtained from newly isolated Acetobacter tropicalis and its comparative study of kinetic parameters with free enzyme

Abstract

Purified Acetobacter tropicalis dextransucrase was immobilized in different matrices viz. calcium-alginate, κ-carrageenan, agar, agarose and polyacrylamide. Calcium-alginate was proved to be superior to the other matrices for immobilization of dextransucrase enzyme. Standardization of immobilization conditions in calcium-alginate resulted in 99.5% relative activity of dextransucrase. This is the first report with such a large amount of relative activity as compared to the previous reports. The immobilized enzyme retained activity for 11 batch reactions without a decrease in activity which suggested that enzyme can be used repetitively for 11 cycles. The dextransucrase was also characterized, which revealed that enzyme worked best at pH 5.5 and 37?°C for 30?min in both the free as well as immobilized state. Calcium-alginate immobilized dextransucrase of A. tropicalis showed the K_m and V_max values of 29?mM and 5000?U/mg, respectively. Free and immobilized enzyme produced 5.7?mg/mL and 2.6?mg/mL of dextran in 2?L bench scale fermenter under optimum reaction conditions. This immobilization method is very unconventional for purified large molecular weight dextran-free dextransucrase of A. tropicalis as this method is used usually for cells. Such reports on entrapment of purified enzyme are rarely documented.     

Effects of entrapment on nucleic acid content,cell morphology,cell surface property,and stress of pure cultures commonly found in biological wastewater treatment

The effects of cell entrapment on nucleic acid content, cell morphology, cell surface property, and stress of major groups of bacteria (betaproteobacteria and gammaproteobacteria) in biological municipal wastewater treatment were investigated. Three different entrapment media (alginate, carrageenan, and polyvinyl alcohol) were examined. Results indicated that the entrapment and type of entrapment media affected nucleic acid content, cell morphology, cell surface property, and stress of the three representative species (Alcaligenes faecalis, Comamonas testosteroni, and Pseudomonas putida) studied. The highest deoxyribonucleic acid and ribonucleic acid increases were observed with the alginate and polyvinyl alcohol (PVA) entrapment, respectively. A cell morphological change from bacilli to coccoidal was observed in the case of alginate entrapment while the PVA-entrapped cells had a slim morphology when compared to non-entrapped cells and formed putative nanowires. The entrapment increased or decreased the surface roughness of cells depending on the type of entrapment media. Expression of a nitrosative stress gene, which is linked to oxygen deprivation, was observed more in the alginate-entrapped cells. These research findings advance the fundamental understanding of the entrapped cell physiology which can lead to more efficient entrapped cell-based wastewater treatment.     

Immobilization of whole cells ofStreptomyces kanamyceticus containing glucose isomerase by a combination of heat treatment in the presence of minerals and entrapment in calcium alginate gels

A method of immobilization of whole cells ofStreptomyces kanamyceticus containing glucose isomerase was devised, based on techniques of heat fixation in the presence of minerals and, entrapment in calcium alginate gels. The optimum activity of the enzyme was obtained when the cells were heat-fixed at 60°C for 10 min in the presence of 50 mmol/L MgSO₄·7H₂O and 5 mmol/L CoCl₂·6H₂O and then cast into calcium alginate beads using 2% sodium alginate.     

Amyloglucosidase enzymatic reactivity inside lipid vesicles

Efficient functioning of enzymes inside liposomes would open new avenues for applications in biocatalysis and bioanalytical tools. In this study, the entrapment of amyloglucosidase (AMG) (EC 3.2.1.3) from Aspergillus niger into dipalmitoylphosphatidylcholine (DPPC) multilamellar vesicles (MLVs) and large unilamellar vesicles (LUVs) was investigated. Negative-stain, freeze-fracture, and cryo-transmission electron microscopy images verified vesicle formation in the presence of AMG. Vesicles with entrapped AMG were isolated from the solution by centrifugation, and vesicle lamellarity was identified using fluorescence laser confocal microscopy. The kinetics of starch hydrolysis by AMG was modeled for two different systems, free enzyme in aqueous solution and entrapped enzyme within vesicles in aqueous suspension. For the free enzyme system, intrinsic kinetics were described by a Michaelis-Menten kinetic model with product inhibition. The kinetic constants, V _max and K _m , were determined by initial velocity measurements, and K _i was obtained by fitting the model to experimental data of glucose concentration-time curves. Predicted concentration-time curves using these kinetic constants were in good agreement with experimental measurements. In the case of the vesicles, the time-dependence of product (glucose) formation was experimentally determined and simulated by considering the kinetic behavior of the enzyme and the permeation of substrate into the vesicle. Experimental results demonstrated that entrapped enzymes were much more stable than free enyzme. The entrapped enzyme could be recycled with retention of 60% activity after 3 cycles. These methodologies can be useful in evaluating other liposomal catalysis operations.     

Chainia Penicillin V Acylase: Strain Characteristics, Enzyme Immobilization, and Kinetic Studies

Aerobic cultures of an actinomycete were found to produce penicillin V acylase (PVA) (PA, EC-3.5.1.11) extracellularly. The presence of L-2-3 diamino-propionic acid in cell wall and formation of sclerotia on culture media led to its identification as Chainia, a sclerotial Streptomyces. Partially purified acylase was adsorbed on kieselguhr and entrapped in polyacrylamide gel. The immobilized preparation proved effective with respect to retention of enzyme and enzyme activity even after 15 successful cycles. The pH optimum for crude enzyme was in the range of pH 7.5–8.0, and for the (NH4)₂ SO₄ fraction it was pH 8.5. The immobilized enzyme showed maximal activity at pH 9.5. The optimum temperature for acylase activity was at 55°C. The crude enzyme, ammonium sulfate fraction, and immobilized enzyme showed K _m value for penicillin V of 6.13 mM, 14.3 mM, and 17.1 mM, respectively. Received: 11 December 1997 / Accepted: 9 April 1998     

Immobilization of goat brain aminopeptidase B in calcium alginate beads

Aminopeptidase B, an arginyl aminopeptidase, was purified from goat brain with a purification factor of ～280 and a yield of 2.7%. It was entrapped in calcium alginate together with bovine serum albumin. The optimal conditions for immobilization for maximum activity yield were 1% CaCl₂ and 2.5% alginate. The immobilized enzyme retained ～62% of its initial activity and could be used for five successive batch reactions with retention of 30% of the initial activity. The pH and temperature optima of the free and immobilized enzyme were pH 7.4, 45°C and pH 7.8, 50°C respectively, while the pH and thermal stability as well as the stability of the enzyme in organic solvents were improved significantly after entrapment. The K_m value for the immobilized enzyme was about twofold higher than that of the soluble enzyme. Because of this increased stability, the immobilized enzyme may be useful in the meat processing industry.     

The action of ultraviolet radiation on yeast catalase

The effect of prolonged UV irradiation (mostly 2537 A) on the catalase activity of an aqueous yeast suspension was divisible into 4 periods. First, the period during which the cells lost their ability to form colonies, but during which no change in catalase activity was noted. Second, the period during which a considerable rise in catalase activity (Euler effect) occurred. The Euler effect was accompanied by enzyme alteration as shown by the simultaneous decrease in the activation energy of the enzyme-substrate system. However, during the initial phase of this period, as the catalase activity of the suspension began to increase, the activation energy rose to a transient level higher even than that characterizing the unaltered enzyme. Heat accelerated the rate of alteration when applied either during or after the irradiation; the activation energy for the over-all alteration reaction was 24 kcal., a value close to that recorded previously for alteration induced by chemical agents. Nevertheless, the rate-limiting step appeared to be different in the two cases. A model of these events was presented in which the primary photochemical action was on the site at which catalase is located within the cell. Third, a rather long period during which irradiation led to no diminution in the catalase activity of the maximally active suspension. This protection effect was duplicated in intro by a model crystalline catalase-KNA system, or by adding either ribonuclease digestion products of RNA or adenine to a catalase solution prior to irradiation. Evidence was adduced that the protection effect was not a simple screening, but involved some sort of interaction between the enzyme and the nitrogenous components of RNA, an interaction which must likewise occur within the cell. Alteration induced by CHCl₃ did not eliminate the protection effect, but that by butanol did. The onset of photoinactivation was due to modification of protein structure, not of RNA. Fourth, the period of photoinactivation of the intracellular enzyme, which was quite similar to that of the crystalline enzyme in vitro.     

Preparation of immobilized enzymes by N-vinylpyrrolidone and the general properties of the glucoamylase gel

Immobilized glucoamylase, invertase, and β-galactosidase were prepared by using N-vinylpyrrolidone monomer (VP) under γ-ray irradiation. The enzyme-VP solutions were gelled by irradiation with 2.9 Mrad and the added enzymes were almost completely entrapped. Activity losses on entrapping were 55% for the VP-glucoamylase gel, and more than 90% in the case of VP-invertase and VP-β-galactosidase gels. No leakage of enzyme from these gels could be detected within 1 hr. The VP-glucoamylase gel was capable of hydrolyzing dextrin (mol wt 10,400) to glucose and the glucose equivalent was equal to that obtain able with native enzyme. The optimum temperature, heat stability, pH activity curve, and pH stability of VP-glucoamylase gel were slightly inferior to those of native enzyme, while Km was a little larger than that of native enzyme.     

Synthesis of l-Tryptophan from Indole and dl-Serine by Tryptophan Synthetase Entrapped in Fibres

Optimal culture conditions for microbial production of tryptophan synthetase were studied. It was found that on cultivation of Escherichia coli 476, a tryptophan auxotroph, in a medium containing 5g/liter glycerol as C source, supplemented with 1 g/liter of acid-treated peptone, cells with high tryptophan synthetase activity could be obtained.

The enzyme was extracted from cells and 3-fold purified by heat treatment and ammonium sulfate precipitation. The overall yield of the isolation procedure was 60%.

The partially purified tryptophan synthetase was entrapped in cellulose triacetate fibres. Under storage conditions, in refrigerator, the entrapped enzyme was stable at least for 6 months. The activity of the entrapped enzyme was about 75% with respect to the free enzyme.

Similar behaviour for the free and entrapped enzyme was observed as to the effect of temperature and pH on the enzymic activity. The operational stability of the entrapped tryptophan synthetase was very good (activity unchanged after 50 days) provided the accumulation of indole on the fibres was avoided.     

Immobilization and characterization of lipase from an indigenous Bacillus aryabhattai SE3-PB isolated from lipid-rich wastewater

Abstract

Extracellular lipase from an indigenous Bacillus aryabhattai SE3-PB was immobilized in alginate beads by entrapment method. After optimization of immobilization conditions, maximum immobilization efficiencies of 77%?±?1.53% and 75.99%?±?3.49% were recorded at optimum concentrations of 2% (w/v) sodium alginate and 0.2?M calcium chloride, respectively, for the entrapped enzyme. Biochemical properties of both free and immobilized lipase revealed no change in the optimum temperature and pH of both enzyme preparations, with maximum activity attained at 60?°C and 9.5, respectively. In comparison to free lipase, the immobilized enzyme exhibited improved stability over the studied pH range (8.5–9.5) and temperature (55–65?°C) when incubated for 3?h. Furthermore, the immobilized lipase showed enhanced enzyme-substrate affinity and higher catalytic efficiency when compared to soluble enzyme. The entrapped enzyme was also found to be more stable, retaining 61.51% and 49.44% of its original activity after being stored for 30 days at 4?°C and 25?°C, respectively. In addition, the insolubilized enzyme exhibited good reusability with 18.46% relative activity after being repeatedly used for six times. These findings suggest the efficient and sustainable use of the developed immobilized lipase for various biotechnological applications.     

Immobilization of catalase via adsorption onto -histidine grafted functional pHEMA based membrane

Poly(2-hydroxyethylmethacrylate) (pHEMA) based flat sheet membrane was prepared by UV-initiated photopolymerization technique. The membrane was then grafted with -histidine. Catalase immobilization onto the membrane from aqueous solutions containing different amounts of catalase at different pH was investigated in a batch system. The maximum catalase immobilization capacity of the pHEMA–histidine membrane was 86 μg cm⁻². The activity yield was decreased with the increase of the enzyme loading. It was observed that there was a significant change between V_max value of the free catalase and V_max value of the adsorbed catalase on the pHEMA–histidine membrane. The K_m value of the immobilized enzyme was higher 1.5 times than that of the free enzyme. Optimum operational temperature was 5°C higher than that of the free enzyme and was significantly broader. It was observed that enzyme could be repeatedly adsorbed and desorbed without loss of adsorption capacity or enzyme activity.     

Methanol metabolism in a peroxisome-deficient mutant of Hansenula polymorpha: a physiological study

We have studied methanol-utilization in a peroxisome-deficient (PER) mutant of Hansenula polymorphoa. In spite of the fact that in carbon-limited chemostat cultures under induced conditions the enzymes involved in methanol metabolism were present at wild-type (WT) levels, this mutant is unable to grow on methanol as a sole carbon and energy source. Addition of methanol to glucose-limited (S_R=12.5mM) chemostat cultures of the PER mutant only resulted in an increase in yield when small amounts were used (up to 22.5 mM). At increasing amounts however, a gradual decrease in cell density was observed which, at 80 mM methanol in the feed, had dropped below the original value of the glucose-limited culture. This reduction in yield was not observed when increasing amounts of formate instead of methanol were used as supplements for the glucose-limited mutant culture and also not in WT cells, used as control in these experiments. The effect of addition of methanol to a glucose-limited PER culture was also studied in the transient state during adaptation of the cells to methanol. The enzyme patterns obtained suggested that the ultimate decrease in yield observed at enhanced methanol concentrations was due to an inefficient methanolmetabolism as a consequence of the absence of peroxisomes. The absence of intact peroxisomes results in two major problems namely i) in H₂O₂-metabolism, which most probably is no longer mediated by catalase and ii) the inability of the cell to control the fluxes of formaldehyde, generated from methanol. The energetic consequences of this metabolism, compared to the WT situation with intact peroxisomes, are discussed.Abbreviations AO alcohol oxidase - DHAS dihydroxyacetone synthase - WT wild-type - PER peroxisome-deficient - GSH reduced glutathione - GSSG glutathione disulphide     

Immobilization of alcohol dehydrogenase by gel entrapment of cells of Saccharomyces cerevisiae

A stable immobilized preparation of alcohol dehydrogenase (ADH) (EC 1.1.1.1) was obtained by entrapment of ADH-containing Saccharomyces cerevisiae cells in polyacrylamide, polymerized by gamma-rays (100 kR). The permeability barrier for the substrate through the cell membrane was found to be eliminated on entrapment. The stability characteristics, pH-activity profile and other properties of the entrapped ADH are presented. A four-fold enhancement in K_m for NAD⁺ was observed on entrapment, whereas K_m for ethanol was not altered.     

Resistance of Penicillium piceum F-648 to Hydrogen Peroxide under Short-Term and Prolonged Oxidative Stress

Resistance of Penicillium piceumF-648 to hydrogen peroxide under short-term and prolonged oxidative stress was studied. An increase in the activity of intracellular catalase in fungal cells after short-term exposure to hydrogen peroxide was shown. Activation of fungal cells induced by H₂O₂ depends on the H₂O₂ concentration, time of exposure, and growth phase of the fungus. Variants of P. piceum F-648 that produced two forms of extracellular catalase with different catalytic properties were obtained due to prolonged adaptation to H₂O₂. Catalase with low affinity for substrate was produced predominantly by the parent culture and variant 3; however, a high substrate affinity of catalase was observed in variant 5. Variant 5 of P. piceum F-648 displayed a high catalytic activity and operational stability of catalase in the presence of phosphate ions and a concentration of substrate less than 30 mM at pH more than 7.