Abstract
The enzyme cyclomaltodextrin-glucanotransferase (CGTase) is a transglicosidase able to convert corn starch into cyclodextrin (CD). CDs are widely applied in industry given the ability to form inclusion complexes with a great variety of organic molecules. Regarding the optimum pH of CGTase, values reported in the literature vary according to the enzyme producing microorganism, being 8.0 the optimum pH of CGTase produced by Bacillus firmus Strain No. 37. This work studied the influence of the pH of culture medium with different concentration of nutrients on the production of the enzyme CGTase by Bacillus firmus Strain No. 37. For this purpose, the microorganism was grown in three culture media with different concentrations of carbon and nitrogen. The pH control was performed by adding sodium carbonate. The fermentation process was analyzed by the following methods: Bradford (1976) method to determine soluble proteins, DNS method to analyze sugars, and the method of complexation with β-CD to analyze the enzyme activity. The best result for CGTase enzyme activity was 0.22 U mL -1 , obtained with medium containing 2.0% soluble corn starch and yeast extract, and pH 8.3.
Highlights
The enzyme CGTase is responsible for catalyzing the formation of cyclodextrin from starch or related sugars
We report the cultivation of Bacillus firmus Strain No 37 for the production of CGTase in culture media with different concentrations of carbon and nitrogen source, under controlled pH
The microorganism was seeded in Petri dishes containing semi-solid medium, whose composition was in w v-1: 1.0% soluble corn starch, 0.5% peptone, 0.5% yeast extract, 0.1% K2HPO4, 0.02% MgSO4.7H2O, 1.0% Na2CO3 and 1.5% agar
Summary
The enzyme CGTase is responsible for catalyzing the formation of cyclodextrin from starch or related sugars. The most common are α-, β- and γ-CD containing 6, 7 and 8 glucosyl residues, respectively The attraction of these cyclic, torus-shaped oligosaccharides arises from their ability to form inclusion complexes with a wide variety of organic molecules. Concerning the optimum pH to CGTase, the values reported in the literature vary according to the species of microorganism that produce the enzyme. Preliminary cultivation of Bacillus firmus Strain No 37 for producing the enzyme CGTase showed that high concentration of soluble corn starch has increased the consumption of sugar by the microorganism with a consequent reduction of pH in the culture medium. We report the cultivation of Bacillus firmus Strain No 37 for the production of CGTase in culture media with different concentrations of carbon and nitrogen source, under controlled pH
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