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Biomedical subjects

N G Karanth

Publications and source records attributed to N G Karanth.

35 records · Page 2Linked to original sources
PubMed1999

Separation and direct detection of raw and gelatinized starch hydrolyzing activities of glucoamylase on isoelectric focusing gels.

A procedure to detect raw and gelatinized starch activities of glucoamylase on isoelectric focusing (IEF) gels by using 2, 3, 5-triphenyltetrazolium chloride is described. The reagent reacts with the reducing group of glucose released by glucoamylase from the substrate starch. Using the reaction, production of glucoamylase by Aspergillus niger was detected on 10% IEF gels within a pH range of 2.5-9.5. Since the method can detect raw and gelatinized starch activities of glucomylase associated with 1 microg protein, it will be useful for enzyme engineering studies that involve screening of various mutations.

Aspergillus niger↗
PubMed1999

Characterisation of a starch-hydrolysing enzyme of Aspergillus niger.

A UV-induced mutant strain of Aspergillus niger (CFTRI-1105-U9) overproduced a starch-hydrolysing enzyme with properties characteristically different from the known amylases of the fungus. The purified enzyme of 4.0 pI had an apparent molecular mass of 125 kDa and it dextrinised starch and then saccharified the dextrins. Patterns of the enzyme activity on starch, resulting in glucose at 60 degrees C and glucose, maltose and maltodextrins at 70 degrees C as primary products, suggested significant applications for the enzyme in starch-processing industries.

Aspergillus niger↗
PubMed1999

Preparation of stearoyl lactic acid ester catalyzed by lipases from Rhizomucor miehei and porcine pancreas optimization using response surface methodology.

The esterification reaction between stearic acid and lactic acid using Rhizomucor miehei lipase and porcine pancreas lipase was optimized for maximum esterification using response surface methodology. The formation of the ester was found to depend on three parameters namely enzyme/substrate ratio, lactic acid (stearic acid) concentration and incubation period. The maximum esterification predicted by theoretical equations for both lipases matched well with the observed experimental values. In the case of R. miehei lipase, stearoyl lactic acid ester formation was found to increase with incubation period and lactic acid (stearic acid) concentrations with maximum esterification of 26.9% at an enzyme/substrate (E/S) ratio of 125 g mol-1. In the case of porcine pancreas lipase, esterification showed a steady increase with increase in incubation period and lactic acid (stearic acid) concentration independent of the E/S ratios employed. In the case of PPL, a maximum esterification of 18.9% was observed at an E/S ratio of 25 g mol-1 at a lactic acid (stearic acid) concentration of 0.09 M after an incubation period of 72 h.

Analysis of Variance↗
PubMed1998

An enzyme-linked immunosorbent assay for the estimation of fungal biomass during solid-state fermentation.

An enzyme-linked immunosorbent assay for sensitive, specific and quantitative estimation of fungal biomass during solid-state fermentation is described. Using this method, differential growth rates and colonization of the substrate can be studied. The assay has potential application for the efficient monitoring of solid-state fermentation involving specific fungus, for which available methods are not adequate.

Antibodies, Fungal↗
PubMed1994

Interaction of transport resistances with biochemical reaction in packed-bed solid-state fermentors: effect of temperature gradients.

In solid-state fermentation, the interaction of transport phenomena with biochemical reactions has a considerable effect on the productivity of the bioreactor. Previous work on solid-state fermentation in tray fermentors in our laboratory indicated that heat transfer resistance results in steep temperature gradients within the solid substrate bed, which in turn adversely affect the biochemical reaction and enzyme activity. This problem of heat accumulation during the course of fermentation has been alleviated to a considerable extent using a packed-column bioreactor with forced aeration in the present work. Experimental studies were conducted in a packed-column bioreactor utilizing wheat bran as substrate and the fungus Aspergillus niger CFTRI 1105 for the production of the enzyme amyloglucosidase. The enzyme activities were estimated and temperatures were recorded at different bed heights, for different air flow rates during the course of fermentation. The results indicated that the temperature gradients caused by heat transfer resistances were reduced considerably with corresponding increases in enzyme activity.

Aspergillus niger↗
PubMed1994

Biodegradation of hexachlorocyclohexane isomers in soil and food environment.

Persistence of chlorinated hydrocarbon insecticides in the environment is well documented. One early introduced insecticide, hexachlorocyclohexane (HCH), popularly called BHC, was used in large quantities all over the world until recently. In India, even today, technical grade HCH is being used extensively. Theoretically, HCH has eight possible stereoisomers of which four (alpha, beta, gamma, and delta) predominate in the technical product. These isomers significantly differ between themselves with respect to their persistence and toxicity toward insects, birds, mammals, and other nontarget organisms. The relative proportion of HCH isomers is, therefore, crucial from a toxicology standpoint. This problem assumes importance in light of reports that the HCH isomers undergo interconversion in soil, water, animals, plants, insects, etc. The persistence of HCH can be attributed in part to the interconversion of HCH isomers, which also restrict their solubility. In the present review, biotransformation of HCH isomers, both under aerobic and anaerobic conditions, and their degradation pathways have been described. In addition, emphasis is given to the interconversion of HCH isomers, including interconversion mechanisms, as this area has not received adequate coverage in earlier reviews on HCH.

Aerobiosis↗
PubMed1993

Interaction of transport resistances with biochemical reaction in packed bed solid state fermenters: the effect of gaseous concentration gradients.

Mass transfer plays an important role in solid state fermentation (SSF) systems. Earlier work on SSF in tray bioreactors indicated that steep gaseous concentration gradients developed within the substrate bed, owing to mass transfer resistances, which may adversely affect the bioreactor performance. For all practical purposes these gradients have been eliminated using a packed bed column bioreactor with forced aeration. Gaseous concentrations (oxygen and carbon dioxide) and enzyme activities were measured at various bed heights for various air flow rates during the course of fermentation. The results indicated that concentration gradients were decreased effectively by increasing air flow rate. For example, the actual oxygen and carbon dioxide concentration gradients reduced from 0.07% (v/v) cm-1 and 0.023% (v/v) cm-1 to 0.007% (v/v) cm-1 and 0.0032% (v/v) cm-1 respectively when the air flow rate was increased from 5 dm3 min-1 to 25 dm3 min-1. This resulted in an overall improvement in the performance of the bioreactor in terms of enzyme production.

Aspergillus niger↗
PubMed1993

Downstream processing of microbial rennet from solid state fermented moldy bran.

In recent years due to acute shortage of calf-rennet, microbial rennets seem to be an effective alternative and are commercially produced. Mucor miehei was cultivated under the solid state fermentation conditions, and the moldy bran was extracted using a semicontinuous multiple contact forced percolation method. The treated extract was then filtered through 5% R16 clay which enabled easy and efficient removal of impurities such as lipase and protease without involving costly chemical treatments. The ethyl alcohol precipitated enzyme was dried and made into powder form having activity of 1.5 x 10(5)Soxhlet units/gm.

Journal Article↗
PubMed1993

Gas concentration and temperature gradients in a packed bed solid-state fermentor.

In solid-state fermentation (SSF), interaction of heat and mass transfer with biochemical reaction (growth associated enzyme production) affects the bioreactor performance. This interaction was earlier observed to cause temperature and gaseous concentration gradients which reduced the effective bed height of the bioreactor. Since forced aeration is known to alleviate this problem, a packed column bioreactor with forced aeration was employed in the present study. Using wheat bran and Aspergillus niger CFTRI 1105, experiments were conducted for the production of the enzyme amyloglucosidase at various air flow rates. Temperatures and gas concentrations were recorded and enzyme activities estimated at different bed heights during the course of SSF. Gas concentration and temperature gradients decreased with increasing air flow rate. The packed column allowed the use of larger bed heights and yielded higher enzyme activities (6,260 Units/gDMB) than trays (345 Units/gDMB). Enzyme activity was affected more by temperature than concentration gradients, and increased with air flow rates.

Journal Article↗
PubMed1983

Insecticide fingerprinting technique for detection and location of organochlorine insecticide residues in foods.

Insecticide fingerprinting technique enables the detection and location of DDT and HCH residues in vegetables through the development of green and prussian blue colors respectively. Cut vegetables are pressed against o-tolidine impregnated paper and exposed to sunlight where colored spots appear instantly. The studies on 18 vegetable varieties revealed the pesticide residues and their distribution in different tissues. This direct method is sensitive (0.3/micrograms for HCH & 0.5/micrograms for DDT) and has special applications in quality control laboratories and food industry.

DDT↗
PubMed1980

Use of modified double-reciprocal plot for enzyme kinetic parameters. A pitfall.

The modified double-reciprocal plot suggested by Lee and Wilson (Lee, H.J. and Wilson, I.B. (1971) Biochim. Biophys. Acta 242, 519--522) has until now been accepted as giving a simple and accurate method for the determination of enzyme kinetic parameters V and Km, which can be used with little error even when as much as 50% of the substrate is consumed. In this paper it has been shown with analytical proof that the errors in the application of their method can in fact be much higher and that the integrated Michaelis-Menten equation should be used in its complete form.

Enzymes↗
PubMed1974

Conversion of Dexon (p-dimethylaminobenzenediazo sodium sulfonate) to N, N-dimethyl-p-phenylenediamine by Pseudomonas fragi Bk9.

The metabolism of the fungicide Dexon (p-dimethylaminobenzenediazo sodium sulfonate) by a soil bacterium is reported for the first time. The organism which is capable of using Dexon only by a co-metabolic process was obtained by enrichment culture and was identified as Pseudomonas fragi. The first metabolic product of Dexon was identified as N,N-dimethyl-p-phenylenediamine. The presence of an enzyme, p-dimethylaminobenzenediazo sodium sulfonate reductase, capable of reducing Dexon to N,N-dimethyl-p-phenylenediamine has been demonstrated in the cell-free extracts of the organism. The enzyme is found to be in the soluble fraction and requires dithiothreitol as a reductant.

Azo Compounds↗
PubMedDate not supplied

High-cell-density fermentation of recombinant Saccharomyces cerevisiae using glycerol.

To obtain a high cell density of recombinant Saccharomyces cerevisiae (INVSc 1 strain bearing a 2 microm plasmid, pYES2 containing a GAL1 promoter for expression of the beta-galactosidase gene), the yeast was grown with glycerol as the substrate by fed-batch fermentation. The feeding strategy was based on an on-line response of the medium pH to the consumption of glycerol. The approach was to feed excess carbon into the medium to create a benign environment for rapid biomass buildup. During cell growth in the presence of glycerol, the release of protons in the medium caused a decrease in pH and the consumption rate of ammonium phosphate served as an on-line indicator for the metabolic rate of the organism. The extent of glycerol feeding in a fed-batch mode with pH control at 5.0 +/- 0.1 was ascertained from the automatic addition of ammonium phosphate to the medium. The glycerol feeding to ammonium phosphate addition ratio was found to be 2.5-3.0. On the basis of the experiments, a maximum dry cell biomass of 140 g per liter and a productivity of 5.5 g DCW/L/h were achieved. The high cell density of S. cerevisiae obtained with good plasmid stability suggested a simple and efficient fermentation protocol for recombinant protein production.

Bioreactors↗
PubMedDate not supplied

Reversible denaturation behavior of immobilized glucose oxidase.

Glucose oxidase (GOD) was immobilized by using glutaraldehyde crosslinking and various stabilizing agents such as BSA, gelatin, lysozyme, and polyethylenimine (PEI). Studies on the denaturation of the soluble as well as immobilized GOD were carried out for 1 h at various concentrations of guanidine hydrochloride (GdmCl) in 50 mM phosphate buffer, pH 6.0 at 25 +/- 1 degrees C. The soluble enzyme required a GdmCl concentration of 5 M for total activity loss, whereas for GOD immobilized with BSA, gelatin, lysozyme, and heat-inactivated lysozyme, the corresponding GdmCl concentration required was 8 M. GOD immobilized with PEI, however, was more stable and retained 25% activity when denatured for 1 h using 8 M GdmCl. However, after undergoing denaturation for 1 h, GOD immobilized with lysozyme regained 72% original activity within 20 min of renaturation, while GOD immobilized with BSA, PEI, gelatin, and heat-inactivated lysozyme regained only 39, 21, 20, and 25% of activity, respectively. After five cycles of repeated denaturation and renaturation with 8 M GdmCl, GOD immobilized with lysozyme retained 70% of the original activity. Refolding ability of lysozyme, glutaraldehyde crosslinkages between lysozyme and GOD, together with ionic interactions between them, appear to play an important role in the denaturation-renaturation behavior of the immobilized enzyme.

Buffers↗