Studies on effect of nutrients on glucose isomerase production by Streptomyces griseus NCIM2020

Abstract

An enzyme which catalyzes the conversion of D-glucose to D-fructose has been demonstrated in cell free extracts of Streptomyces griseus NCIM2020 in submerged fermentation. Cell protein reached maximum at around 3 days of cultivation at 30°C temperature and pH 7.5. During logarithmic phase of growth, intracellular glucose isomerase formation was rapid and rate of formation was almost linear with growth. As a nitrogen source yeast extract, beef extract, malt extract and peptone have stimulating effect on the enzyme production. Addition of Mg2+ to growth medium significantly enhanced the enzyme production, however, organism did not require Co2+ in the growth medium for enzyme production, which is very often required by many microorganism for glucose isomerase production. Xylose in combination with glucose is an excellent carbon source for the production of glucose isomerase and xylose act as an inducer of enzyme synthesis. Streptomyces griseus NCIM2020 produced a significant amount of glucose isomerase when grown on inexpensive agricultural products (hemicellulose of wheat straw and sugarcane bagasse also their acid hydrolysate) in submerged fermentation. The optimum temperature for enzyme activity was 60°C and optimum pH was between 7.0∼8.5 depending upon the type of buffer used. The enzyme extracted in the present study appears very thermotolerant and pH stable.