Biomedical subjects

U C Banerjee

Publications and source records attributed to U C Banerjee.

31 records · Page 2Linked to original sources

PubMed1996

Purification and properties of levanase from Rhodotorula sp.

Levanase, a slime dissolving enzyme of Rhodotorula sp., was purified to approx. 26-fold by ammonium sulphate precipitation, DEAE and gel filtration (Sephacryl S-200) chromatography. The molecular mass of the enzyme was 39 kDa. The purified levanase showed maximum activity at pH 6.0 and 40 degrees C. Enzyme was quite stable at 4 degrees C and at pH 5.5 to 6.5. Hg2+ at a level of 10 mM completely inhibited the levanase activity, while 2-mercaptoethanol at the same concentration showed a 2.93-times increase in activity. In addition to levan, the enzyme also showed substrate specificity towards inulin.

Ammonium Sulfate↗

PubMed1996

Extracellular amylase production by Saccharomycopsis capsularis and its evaluation for starch saccharification.

A strain of starch-assimilating yeast, Saccharomycopsis capsularis, isolated from Indian cereal-based fermented foods, produced significant levels of extracellular alpha-amylase and glucoamylase. The enzymes reached their peak activities during the stationary phase at the end of the 5th and 4th day of cultivation, respectively. The amylase yields were maximized by a proper choice of carbon and nitrogen sources, starting pH of the culture medium and growth temperature. High activities of the enzymes were obtained through inexpensive agricultural commodities, such as wheat bran and corn meal as carbon sources, and defatted soybean meal and peanut meal as nitrogen sources. A temperature of 28-32 degrees C and an initial pH of 4.5-5.0 were optimum. The crude amylase mixture could liquefy and saccharify a 1% starch solution completely in 24 h at 50 degrees C.

Amylases↗

PubMed1994

Disruption of a recombinant yeast for the release of beta-galactosidase.

A recombinant yeast, Saccharomyces cerevisiae, expressing Escherichia coli beta-galactosidase gene under the control of CYC1 constitutive promoter of the yeast, was disrupted in a continuous flow, high speed, bead mill for the release of intracellular beta-galactosidase (EC 3.2.1.23). Release of the beta-galactosidase activity was characterized with respect to glass bead loading in the grinding chamber (70-85% of chamber volume), diameter of the beads (0.25-0.75 mm), number of passes of the cell slurry through the mill (0-6 passes), flow rate of the slurry (25-250 mL.min-1), cell concentration in the slurry (5-20 gDW.L-1), the agitation rotor speed (1000-4000 rpm) and the pH of the slurry (pH 5-10). The optimal conditions for the release of the enzyme were pH 6.0-9.0, 85% loading of 0.5 mm diameter beads and an agitation speed of 2000 rpm. The enzyme release followed first-order kinetics. For otherwise fixed conditions, the extent of cell disruption increase with increasing bead load, number of passes and agitation rotor speed. Cell concentration did not affect disruption. The release of beta-galactosidase activity declined with increasing flow rate of the cell slurry through the mill, but the disruption rate constant increased with flow rate. Under optimal condition, three passes through the grinding chamber were sufficient to release all of the enzyme. In comparison with disruption in the bead mill, chloroform-sodium dodecyl sulfate induced lysis of cells was ineffective in releasing the enzyme quantitatively.

Biotechnology↗

PubMed1993

Transformation of rifamycin B with growing and resting cells of Curvularia lunata.

Growing and resting cell systems of Curvularia lunata were used for the transformation of rifamycin B to rifamycin S. In the case of growing cells, rifamycin B was added at the time of inoculation and at the different phases of growth. Interestingly, it was found that C. lunata could grow in the presence of rifamycin B and could convert rifamycin B to rifamycin S. Growing cells 24 and 48 h of age were capable of transforming rifamycin B. Resting cells, cultivated at the exponential or early stationary phase, were found to be very active, and the resting cells of different ages were repeatedly used for the transformation reaction. Growing cells of 72 and 96 h were not capable of transforming rifamycin B, whereas resting cells of similar ages were very active. Due to the adsorption of rifamycins by the growing and resting cells of C. lunata, the stoichiometric yield of rifamycin S was not obtained.

Biotransformation↗

PubMed1993

Characterization of soluble rifamycin oxidase from Curvularia lunata var. aeria.

Curvularia lunata var. aeria was grown on yeast extract, peptone and carboxymethylcellulose (YPC) medium for the production of extracellular rifamycin oxidase. The enzyme was partially purified through a Sephadex G-75 column. The half lives of rifamycin oxidase at 30 degrees and 40 degrees C were 9 d and 100 min, respectively. The activation and deactivation energies of the partially purified enzyme, calculated from Arrhenius plots, were 5.80 and 35.10 kcal mol-1, respectively. The enzyme exhibited a Km (rifamycin B) value of 0.67 mmol l-1 and a Vmax of 11 mumol h-1.ml. Three metal ions, Fe2+, Ag+ and Hg2+, inhibited the enzyme in the 10-20 mmol l-1 metal ion concentration range. Catalytic activity was not affected by the chelating agent, EDTA.

Enzyme Stability↗

PubMed1993

Studies on rifamycin oxidase immobilized on kappa-carrageenan gel.

Rifamycin oxidase from Curvularia lunata var. aeria was immobilized on kappa-carrageenan gel where the enzyme showed excellent catalyzing activity and operational stability. Factors affecting the activity of immobilized enzyme preparation such as pH and temperature were investigated. Thermostability of the immobilized enzyme preparation was checked at 30 and 40 degrees C and it was found that the thermostability of the immobilized rifamycin oxidase activity has increased compared to free enzyme. Transformation of rifamycin B to rifamycin S was also carried out with the immobilized enzyme preparation. Kappa-carrageenan immobilized rifamycin oxidase was also reused several times for the transformation of rifamycin B to rifamycin S.

Biotransformation↗

PubMed1993

Characterization of rifamycin oxidase immobilized on alginate gel.

Rifamycin oxidase of Curvularia lunata was immobilized on alginate gel. The pH and temperature optima of the immobilized enzyme preparation were 6.5 and 50 degrees C, respectively. Transformation reaction was carried out with the immobilized enzyme preparation. It took 8 h for the complete transformation of rifamycin B (10 g/L) to rifamycin S. The immobilized enzyme preparation was found to be mechanically weak even in the presence of CaCl2 in the reaction mixture. Reusability studies showed that the catalyst can not be repeatedly used very effectively.

Alginates↗

PubMed1992

Immobilized beta-glucosidase from Curvularia lunata.

beta-Glucosidase from Curvularia lunata was immobilized in pellets of polyacrylamide, sodium alginate and agar. The activity of the enzyme was estimated at different times by measuring the absorbance of a solution into which 2-nitrophenol was released by the enzyme. The effect of pH and temperature was studied to select the optimum conditions. Thermostability of the beta-glucosidase in each of the carriers was assessed over a period of 12-26 d. The immobilized enzyme on all the three carriers retained its activity longer than free enzyme did. Polyacrylamide was the best carrier both in terms of thermostability and of reusability of the immobilized enzyme preparations. The Michaelis constant (Km) for each of the immobilized enzyme preparation was calculated.

Enzyme Stability↗

PubMed1992

Biotransformations of rifamycins: process possibilities.

Rifampicin, an important antibiotic, is manufactured by chemical conversion of rifamycin S which is obtained by the chemical modification of rifamycin B. Rifamycin B is a product of Nocardia mediterranei fermentations. The chemical conversion of rifamycin B to rifamycin S has many disadvantages: Strong acidic conditions are required, heavy foam formation accompanies transformation and the yields are low. This review highlights the developments in alternative, biochemical transformations using enzymes and cells; the main focus is on transformations carried out by rifamycin oxidase.

Journal Article↗

PubMed1991

Production of laccase by Curvularia sp.

A Curvularia sp. isolated from soil was found to contain laccase activity toward guaiacol as substrate. The organism produced an extracellular laccase in a medium containing yeast extract, peptone and dextrose. Initial medium pH 4.0 and cultivation temperature 30 degrees C were found to be most suitable for maximum enzyme production. The optimum pH and temperature for laccase activity were found to be 5.2 and 50 degrees C, respectively. Under optimum conditions, the enzyme had a Km (guaiacol) of 0.75 mmol/L and a V of 1.50 CU min-1 ml-1. Some divalent metal ions inhibited laccase activity at very low concentrations.

Hydrogen-Ion Concentration↗

PubMed1986

Effects of certain atmospheric pollutants (SO2, NO2 and CO) on the soluble amino acids, molecular weight and antigenicity of some airborne pollen grains.

The pure pollen grains of Red Oak (Quercus rubra), Meadow Fescue (Festuca elatior) and Chinese Elm (Ulmas pumila) were exposed to carbon monoxide (CO), sulphur dioxide (SO2) and nitrogen dioxide (NO2). After exposure, the soluble free amino acids were determined from the extracts using two-dimensional thin layer chromatography, and the molecular weight of the extracts were determined by SDS-gel electrophoresis (PAGE). The results indicated that after contamination, both the amino acids and molecular weight profiles were changed. In addition, the double immunodiffusion method was used against rabbit-antisera to determine the antigenicity of contaminated and non-contaminated pollen grain extracts. The results also showed that there were antigenic changes after contamination.

Air Pollutants, Occupational↗

PubMedDate not supplied

Production of phytase (myo-inositolhexakisphosphate phosphohydrolase) by Aspergillus niger van Teighem in laboratory-scale fermenter.

The growth and production pattern of phytase by a filamentous fungus, Aspergillus niger van Teighem, were studied in submerged culture at varying agitation rates and controlled and uncontrolled pH conditions. Allowing the initial culture to grow under neutral condition with subsequent decline in pH resulted in increased phytase productivity. A maximum of 141 nkat/mL phytase was obtained when the broth pH was maintained at pH 2.5 as compared to 17 nkat/mL units at controlled pH 5.5. The culture morphology and rheological properties of the fermentation broth significantly varied with the agitation rate. The volumetric oxygen transfer coefficient was determined at different phases of fungal growth during batch fermentation using static gassing out and dynamic gassing out methods. The oxygen transfer coefficient (k(L)a) of the fermenter was found to be 125 h(-)(1) at 500 rpm as compared to 38 h(-)(1) at 200 rpm. The oxygen transfer rates at different phases of growth were significantly affected by cell mass concentration and fungal morphology. During the course of fermentation there was a gradual decline of k(L)a from 97 h(-)(1) on day 2 to 63 h(-)(1) on day 6 of fermentation, after which no significant change was observed. The degree of agitation considerably influenced the culture morphology where shear thinning of filamentous fungus was observed with the increase in agitation.

6-Phytase↗

PubMedDate not supplied

Bioactive compounds from cyanobacteria and microalgae: an overview.

Cyanobacteria (blue-green algae) are photosynthetic prokaryotes used as food by humans. They have also been recognized as an excellent source of vitamins and proteins and as such are found in health food stores throughout the world. They are also reported to be a source of fine chemicals, renewable fuel and bioactive compounds. This potential is being realized as data from research in the areas of the physiology and chemistry of these organisms are gathered and the knowledge of cyanobacterial genetics and genetic engineering increased. Their role as antiviral, anti-tumour, antibacterial, anti-HIV and a food additive have been well established. The production of cyanobacteria in artificial and natural environments has been fully exploited. In this review the use of cyanobacteria and microalgae, production processes and biosynthesis of pigments, colorants and certain bioactive compounds are discussed in detail. The genetic manipulation of cyanobacteria and microalgae to improve their quality are also described at length.

Biological Factors↗