Biomedical subjects

U C Banerjee

Publications and source records attributed to U C Banerjee.

At least 19 recordsLinked to original sources

PubMed2006

Improvement of carbonyl reductase production of Geotrichum candidum for the transformation of 1-acetonaphthone to S(-)-1-(1'-napthyl) ethanol.

The aim of this work was to study the influence of media components and physico-chemical parameters on the growth and carbonyl reductase production by Geotrichum candidum. Under optimized conditions, the conversion of the substrate increased to >93%, while the specific growth rate and enzyme activity were increased by 200% and 29%, respectively. The rate of conversion of the substrate was also very high in the cells grown in optimized medium. The volumetric productivity of the biotransformation process was much higher (0.27g/lh) with the cells grown in the optimized medium compared to that of grown in un-optimized medium (0.16g/lh). The cells were also highly stable in the operational condition, indicating the feasibility of their use in multiple batches of reaction.

Biotransformation↗

PubMed2006

Decolorization of triphenylmethane dye-bath effluent in an integrated two-stage anaerobic reactor.

In the present study, decolorization of a simulated dye waste containing three different triphenylmethane (TPM) dyes--Magenta, Malachite Green and Crystal Violet, was investigated in a laboratory scale, two-stage anaerobic high-rate reactor. The effect of various parameters (influent dye concentration, hydraulic and co-substrate loading rates) on color and COD removal efficiency of the reactor has been studied. It has been shown that the influent dye concentration had little effect on overall COD and color removal efficiency. More than 99% color removal and 96% COD removal efficiency were maintained even at a dye concentration of 500 mg/l and a dye loading rate of 1000 mg/l day. However, a minimum level of glucose as supplementary carbon source is required to maintain the maximum color removal efficiency and it drops appreciably when no glucose is added to the influent. The study also showed that the acidogenic phase of the reaction plays an important role in decolorization of the TPM dyes. In addition, the two-stage anaerobic reactor was observed to have distinct advantages over the single-stage system, as the drop in color and COD removal efficiency of stage 1 are adequately compensated by stage 2 of the reactor especially under high dye loading rates accompanied by low co-substrate loading and under reduced HRTs.

Bacteria, Anaerobic↗

PubMed2006

Enhancing the catalytic potential of nitrilase from Pseudomonas putida for stereoselective nitrile hydrolysis.

(R)-mandelic acid was produced from racemic mandelonitrile using free and immobilized cells of Pseudomonas putida MTCC 5110 harbouring a stereoselective nitrilase. In addition to the optimization of culture conditions and medium components, an inducer feeding approach is suggested to achieve enhanced enzyme production and therefore higher degree of conversion of mandelonitrile. The relationship between cell growth periodicity and enzyme accumulation was also studied, and the addition of the inducer was delayed by 6 h to achieve maximum nitrilase activity. The nitrilase expression was also authenticated by the sodium dodecyl phosphate-polyacrylamide gel electrophoresis analysis. P. putida MTCC 5110 cells were further immobilized in calcium alginate, and the immobilized biocatalyst preparation was used for the enantioselective hydrolysis of mandelonitrile. The immobilized system was characterized based on the Thiele modulus (phi). Efficient biocatalyst recycling was achieved as a result of immobilization with immobilized cells exhibiting 88% conversion even after 20 batch recycles. Finally, a fed batch reaction was set up on a preparative scale to produce 1.95 g of (R)-(-)-mandelic acid with an enantiomeric excess of 98.8%.

Acetonitriles↗

PubMed2005

Purification and characterization of an enantioselective arylacetonitrilase from Pseudomonas putida.

The highly enantioselective arylacetonitrilase of Pseudomonas putida was purified to homogeneity using a combination of (NH4)2SO4 fractionation and different chromatographic techniques. The enzyme has a molecular weight of 412 kDa and consisted of approximately nine to ten identical subunits (43 kDa). The purified enzyme exhibited a pH optimum of 7.0 and temperature optimum of 40 degrees C. The nitrilase was highly susceptible to thiol-specific reagents and metal ions and also required a reducing environment for its activity. These reflected the presence of a catalytically essential thiol group for enzyme activity which is in accordance with the proposed mechanism for nitrilase-catalyzed reaction. The enzyme was highly specific for arylacetonitriles with phenylacetonitrile and its derivatives being the most preferred substrates. Higher specificity constant (kcat/K(m)) values for phenylacetonitrile compared to mandelonitrile also revealed the same. Faster reaction rate achieved with this nitrilase for mandelonitrile hydrolysis was possibly due to the low activation energy required by the protein. Incorporation of low concentration (<5%) of organic solvent increased the enzyme activity by increasing the availability of the substrate. Higher stability of the enzyme at slightly alkaline pH and ambient temperature provides an excellent opportunity to establish a dynamic kinetic resolution process for the production of (R)-(-)-mandelic acid from readily available mandelonitrile.

Acetonitriles↗

PubMed2005

Release of an enantioselective nitrilase from Alcaligenes faecalis MTCC 126: a comparative study.

Nitrilases constitute an important class of hydrolases, however, cheap and ready availability of enzyme sources limit their practical synthetic applications. The present investigation was directed to compare the applicability of various physical cell disintegration methods namely, solid shear, liquid shear and sonication, for the release of an enantioselective nitrilase from Alcaligenes faecalis MTCC 126. Different parameters associated with each method were optimized in order to ensure maximal release of active nitrilase. The methods were also compared under optimal conditions for their efficiency of nitrilase release and extent of cell disruption, and enzyme release were visualized under a differential interference contrast microscope (DIC) and SDS-PAGE, respectively. Maximum release of the enzyme protein from the cells was observed in case of liquid shear method employing high-pressure homogenization, however, the specific activity of nitrilase was highest in cell-free extract (CFE) generated by sonication. Both the solid shear and liquid shear proved to be equally effective for maximum release of intracellular enzymes, however, from the specific activity point of view, sonication was found to be a better one compared to other two methodologies. The generated cell-free extract can be further employed for the production of enantiopure chiral carboxylic acids, which are important chiral building blocks.

Alcaligenes faecalis↗

PubMed2005

Biochemical characterisation of extracellular phytase (myo-inositol hexakisphosphate phosphohydrolase) from a hyper-producing strain of Aspergillus niger van Teighem.

Aspergillus niger van Teighem, isolated in our laboratory from samples of rotten wood logs, produced extracellular phytase having a high specific activity of 22,592 units (mg protein)-1 . The enzyme was purified to near homogeneity using ion-exchange and gel-filtration chromatography. The molecular properties of the purified enzyme suggested the native phytase to be oligomeric, with a molecular weight of 353 kDa, the monomer being 66 kDa. The purified enzyme exhibited maximum activity at pH 2.5 and 52-55 degrees C. The enzyme retained 97% activity after a 24-h incubation at 55 degrees C in the presence of 10 mM glycine, while 87% activity was retained when no thermoprotectant was added. Phytase activity was not affected by most metal ions, inhibitors and organic solvents. Non-ionic and cationic detergents (0.1-5%) stabilise the enzyme, while the anionic detergent (SDS), even at a 0.1% level, severely inhibited enzyme activity. The chaotropic agents guanidinium hydrochloride, urea, and potassium iodide (0.5-8 M), significantly affected phytase activity. The maximum hydrolysis rate (Vmax) and apparent Michaelis-Menten constant (Km) were 1,074 IU/mL and 606 microM, respectively, with a catalytic turnover number of 3x10(5) s-1 and catalytic efficiency of 3.69x10(8) M-1 s-1.

6-Phytase↗

PubMed2005

Biotransformations for the production of the chiral drug (S)-Duloxetine catalyzed by a novel isolate of Candida tropicalis.

A yeast strain, Candida tropicalis PBR-2, isolated from soil, is capable of carrying out the enantioselective reduction of N,N-dimethyl-3-keto-3-(2-thienyl)-1-propanamine to (S)-N,N-dimethyl-3-hydroxy-3-(2-thienyl)-1-propanamine, a key intermediate in the synthesis of the chiral drug (S)-Duloxetine. The organism produced the enantiopure (S)-alcohol with a good yield (> 80%) and almost absolute enantioselectivity, with an enantiomeric excess (ee) > 99%. Parameters of the bioreduction reaction were optimized and the optimal temperature and pH for the reduction were found to be 30 degrees C and 7.0, respectively. The optimized substrate and the resting cell concentration were 1 g/l and 250 g/l, respectively. The preparative-scale reaction using resting cells of C. tropicalis yielded the (S)-alcohol at 84-88% conversion and ee > 99%.

Biodegradation, Environmental↗

PubMed2004

Streptokinase--a clinically useful thrombolytic agent.

A failure of hemostasis and consequent formation of blood clots in the circulatory system can produce severe outcomes such as stroke and myocardial infraction. Pathological development of blood clots requires clinical intervention with fibrinolytic agents such as urokinase, tissue plasminogen activator and streptokinase. This review deals with streptokinase as a clinically important and cost-effective plasminogen activator. The aspects discussed include: the mode of action; the structure and structure-function relationships; the structural modifications for improving functionality; recombinant streptokinase; microbial production; and recovery of this protein from crude broths.

Fibrinolysis↗

PubMed2003

A high-throughput amenable colorimetric assay for enantioselective screening of nitrilase-producing microorganisms using pH sensitive indicators.

Based on the color change of an indicator due to the release of hydrogen ion from a nitrilase-catalyzed reaction, a rapid colorimetric method was established for the enantioselective screening of nitrilase-producing microorganisms. The formation of acids due to the nitrilase-mediated hydrolysis of nitriles causes a drop in the pH, which in turn results in a change of color of the solution (containing indicator) that can be observed visually. The buffer (0.01 M phosphate, pH 7.2) and indicator (Bromothymol blue, 0.01%) were selected in such a way that both have the same affinity for the released protons. The enantioselectivity of nitrilases was estimated by comparing the hydrolysis of (R)-mandelonitrile with that of racemate under the same conditions. The method was used to screen a library of nitrilase-producing microorganisms, isolated in the authors' laboratory for their ability to enantioselectively hydrolyze mandelonitrile to mandelic acid, an important chiral building block.

Acetonitriles↗

PubMed2002

The nitrile-degrading enzymes: current status and future prospects.

Nitrile-converting enzymes are becoming commonplace in the synthesis of pharmaceuticals and commodity chemicals. These versatile biocatalysts have potential applications in different fields including synthetic biocatalysis and bioremediation. This review attempts to describe in detail the three major classes of nitrile-converting enzymes, namely nitrilases, nitrile hydratases and amidases. Various aspects of these enzymes including their occurrence, mechanism of action, characteristics and applicability in different sectors have been elaborately elucidated. Cloning of genes related to nitrile-converting enzymes is also discussed.

Amidohydrolases↗

PubMed2002

Biotechnological applications of cyclodextrins.

Cyclodextrins (CDs) are a family of cyclic oligosaccharides that are composed of alpha-1,4-linked glucopyranose subunits. Cyclodextrins are produced from starch by enzymatic degradation. These macrocyclic carbohydrates with apolar internal cavities can form complexes with and solubilize many normally water-insoluble compounds. This review describes recent applications of CDs in pharmaceuticals with a major emphasis on drug delivery systems. The utility of these water-soluble cyclic glucans in a variety of foods, flavors cosmetics, packaging and textiles is elaborated. The role of these compounds in biocatalysis is also discussed. Cyclodextrins are used in separation science because they have been shown to discriminate between positional isomers, functional groups, homologues and enantiomers. This property makes them a useful agent for a wide variety of separations.

Journal Article↗

PubMed2002

Botryococcus braunii: a renewable source of hydrocarbons and other chemicals.

Botryococcus braunii, a green colonial microalga, is an unusually rich renewable source of hydrocarbons and other chemicals. Hydrocarbons can constitute up to 75% of the dry mass of B. braunii. This review details the various facets of biotechnology of B. braunii, including its microbiology and physiology; production of hydrocarbons and other compounds by the alga; methods of culture; downstream recovery and processing of algal hydrocarbons; and cloning of the algal genes into other microorganisms. B. braunii converts simple inorganic compounds and sunlight to potential hydrocarbon fuels and feedstocks for the chemical industry. Microorganisms such as B. braunii can, in the long run, reduce our dependence on fossil fuels and because of this B. braunii continues to attract much attention.

Biotechnology↗

PubMed2001

Production, purification, characterization, and applications of lipases.

Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) catalyze the hydrolysis and the synthesis of esters formed from glycerol and long-chain fatty acids. Lipases occur widely in nature, but only microbial lipases are commercially significant. The many applications of lipases include speciality organic syntheses, hydrolysis of fats and oils, modification of fats, flavor enhancement in food processing, resolution of racemic mixtures, and chemical analyses. This article discusses the production, recovery, and use of microbial lipases. Issues of enzyme kinetics, thermostability, and bioactivity are addressed. Production of recombinant lipases is detailed. Immobilized preparations of lipases are discussed. In view of the increasing understanding of lipases and their many applications in high-value syntheses and as bulk enzymes, these enzymes are having an increasing impact on bioprocessing.

Journal Article↗

PubMed2000

Production, purification, and characterization of the debittering enzyme naringinase.

This review discusses the debittering enzyme naringinase and its essential role in the commercial processing of citrus fruit juice. Applications of this enzyme in other areas are identified. Characterization of the enzyme is detailed and its immobilized preparations are discussed. Production of microbial naringinase by fermentation is described.

Journal Article↗

PubMed1999

Characterization and some reaction-engineering aspects of thermostable extracellular beta-galactosidase from a new Bacillus species.

A new strain of Bacillus sp. was isolated from a hot water spring in India. This strain generated a high activity of extracellular beta-galactosidase at 37 degrees C in shake flasks. The beta-galactosidase activity was found to increase continuously but the production rate was slower than with some other organisms reported in the literature. There were noteworthy differences in the time-domain profiles of bacterial concentration and beta-galactosidase activity when the starting concentration of substrate (glucose) was tripled from 10 g/L. These differences may be explained in terms of the relative rates of enzyme synthesis and its diffusion across the cell wall. The enzyme produced by this organism is more stable than other beta-galactosidases; its half-life is 408 h at 50 degrees C and 94 h at 55 degrees C, while the reported enzymes showed perceptible loss of activity within 2 h.

Bacillus↗

PubMed1998

Biodegradation of triphenylmethane dyes.

Biodegradation of triphenylmethane dyes by bacteria, actinomycetes, yeasts, and fungi are discussed in detail. The disadvantages of physical and chemical treatment processes of dye wastewater are also discussed. Biological treatment processes have many advantages over the chemical and physical treatment processes such as possibility of degradation of dye molecules to carbon dioxide and water and formation of less sludge in addition to being environmentally friendly. This group of dyes is toxic depending on the concentration used. Toxicity of triphenylmethane dyes is discussed with respect to different organisms. Some aspects of biodegradative products of this group of dyes are also mentioned.

Bacteria↗

PubMed1998

Comparison of static and shake culture in the decolorization of textile dyes and dye effluents by Phanerochaete chrysoporium.

Decolorization of several dyes (Red HE-8B, Malachite Green, Navy Blue HE-2R, Magenta, Crystal Violet) and an industrial effluent with growing cells of Phanerochaete chrysosporium in shake and static culture was demonstrated. All the dyes and the industrial effluent were decolorized to some extent with varying percentages of decolorization (20-100%). The rate of decolorization was very rapid with Red HE-8B, an industrial dye. Decolorization rates for all the dyes in static condition were found to be less than the shake culture and also dependent on biomass concentration.

Basidiomycota↗

PubMed1997

Production and properties of L-asparaginase from Mucor species associated with a marine sponge (Spirastrella sp.).

The fungus Mucor sp. isolated from the marine sponge Spirastrella sp. produced extracellular L-asparaginase. The maximum L-asparaginase activity was found at 50 degrees C. The activation and deactivation energies of the partially purified enzyme were 9.58 and 21.69 kcal mol-1, respectively. The enzyme activity was not affected by the addition of 4% (w/v) NaCl and different metal ions (Co+2, Fe+2, Mg+2, Ni+2, and Zn+2) at 25 mmol l-1 but was strongly inhibited by EDTA.

Animals↗