S. K. Majumdar

Studies on nutritional and oxygen requirements for production of L-asparaginase by Enterobacter aerogenes.

Abstract The carbon and nitrogen sources most suitable for L-asparaginase production by Enterobacter aerogenes were selected and their concentrations optimized in shake-flask cultures. Sodium citrate (1.0%) and diammonium hydrogen phosphate (0.16%) proved to be the best sources of carbon and nitrogen, respectively. Nitrogen catabolite repression of enzyme formation was absent in this bacterium. Cultivation in a reactor showed that the dissolved oxygen level is the limiting factor for L-asparaginase production by E. aerogenes. Glucose was found to be a repressor of enzyme synthesis. Asparagine was absent intracellularly when the L-asparaginase level was high. An increase in the extracellular alanine level when the dissolved oxygen remained low indicated a shift from aerobic to fermentative metabolism.

Effect of minerals on the production of the delta endotoxin byBacillus thuringiensis subsp.israelensis

SummaryA study has been made of the mineral requirements ofBacillus thuringiensis subsp.israelensis for production of the mosquitocide delta endotoxin. The optimum concentrations of K2HOP4, MgSO4.7H2O and CaCO3 for toxin production are 1g/l, 0.3g/l and 1g/l respectively while the elements Fe, Mn, Cu are required at levels of 2 μg/ml, 5 μg/ml and 0.25 μg/ml respectively.

Characteristics of yeast β-galactosidase immobilized on calcium alginate gels

SummarySaccharomycesanamensis having β-galactosidase activity, has been immobilized in calcium alginate gel matrix that retained 78.6% enzyme activity to that of native cells. Optimum pH(7.0) was negligibly affected by immobilization. Km values for immobilized and native cells were 119 mM and 102 mM respectively. Protective agents like dithioerythritol, bovine serum albumin, enhance the enzyme activity when added prior to immobilization. Immobilized cells can be stored in refrigeration(4°C) for 42 days without a significant loss of enzyme activity.

Glucose isomerase activity of streptomyces kanamyceticus

SummaryStreptomyceskanamyceticus produces a significant level of intracellular glucose isomerase when grown in submerged culture. The optimum temperature for enzyme activity is 90°C, but the optimum pH is changed by the kinds of buffer solution used. The activity is higher at pH 7.0–9.5. Treatment of cells with cetyl trimethyl ammonium bromide extracts almost the same amount of the enzyme as ultrasonic treatment. The selection of the method of treatment for enzyme extraction depends, however, on the nature of cell growth in synthetic or complex medium.

Effect of minerals on glucose isomerase production by Streptomyces kanamyceticus

SummaryA study has been made of the mineral requirements of Streptomyces kanamyceticus KCC S-0433 for production of glucose isomerase. The optimal concentrations of MgSO4 and K2HPO4 for enzyme production are 0.07% and 0.05%, respectively. The elements Fe, Mn and Zn are required at levels of 10, 3 and 3 mg/l, respectively. Cu, Co and Ca have inhibitory effects on the production of the enzyme.

Preparation and properties of glucose isomerase of Streptomyces kanamyceticus cells entrapped in calcium alginate

SummaryThe properties of glucose isomerase in native, heat-treated and immobilized cells of Streptomyces kanamyceticus after heat and mineral treatment have been compared. The optimum pH for glucose isomerase in native cells was shifted from 8.2 to 8.6 by heat treatment and immobilization. There is no change in the optimum temperature (90°C) for activity of the enzyme by the above treatment. Heat-treated cells and immobilized cells show greater pH and thermal stability of the enzyme. The Km values of the enzyme of native cells, heat-treated cells and immobilized heat-mineral-treated cells are 208 mM, 212 mM and 166 mM respectively; Mg++ and Co++ enhance the activity of isomerase in all cases.

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.