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Interference of thiol-compounds with dextrinizing activity assay of alpha-amylase by starch-iodine colour reaction: modification of the method to eliminate this interference.

Manonmani, H. K. and Kunhi, A. A. M. (1999) Interference of thiol-compounds with dextrinizing activity assay of alpha-amylase by starch-iodine colour reaction: modification of the method to eliminate this interference. World Journal of Microbiology and Biotechnology, 15 (4). 485-487, 6 ref..

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Abstract

During microbial production of alpha-amylases (EC 3.2.1.1), enzyme activity is commonly measured by estimation of dextrinizing activity in a starch-iodine colour assay using culture filtrates as the enzyme source. However, previous studies have shown that medium constituents can interfere with colour complex formation. In this study, the interfering substance(s) was investigated and the method was modified so as to eliminate this interference. Interference was found to be due to thiol groups present in the medium which compete with starch for iodine. Among the various metal salts tested for counteracting the interference, ZnSO4 was found to be the best, reverting the colour to approx. 73-85% that of the blank. A combination of hydrogen peroxide (10 mul of 30% solution) and CuSO4 . 5H2O (50 mul of 0.1M solution) completely protected the starch-iodine reaction in the presence of 0.5 ml Luria broth and a modified assay was developed based on this finding. Colour intensity, however, was almost double that obtained for the same amount of starch and iodine in the absence of these protective agents. Nevertheless, with different concn. of starch, as well as with varying amounts of enzymes, the modified method showed perfect linearity and could be used effectively for estimation of dextrinizing activity of alpha-amylase in the presence of thiol groups.

Item Type: Article
Uncontrolled Keywords: AMYLASES-; ANALYTICAL-TECHNIQUES; MICROBIOLOGICAL-TECHNIQUES; alpha-AMYLASES; ASSAY-; INTERFERENCE-; MEDIA-
Subjects: 600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
Divisions: Food Microbiology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 30 Jun 2009 09:43
Last Modified: 14 Dec 2016 12:22
URI: http://ir.cftri.com/id/eprint/7725

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