Enzymatic reduction of azo and indigoid compounds

A customer- and environment-friendly method for the decolorization azo dyes was developed. Azoreductases could be used both to bleach hair dyed with azo dyes and to reduce dyes in vat dyeing of textiles. A new reduced nicotinamide adenine dinucleotide-dependent azoreductase of Bacillus cereus, which showed high potential for reduction of these dyes, was purified using a combination of ammonium sulfate precipitation and chromatography and had a molecular mass of 21.5 kDa. The optimum pH of the azoreductase depended on the substrate and was within the range of pH 6 to 7, while the maximum temperature was reached at 40°C. Oxygen was shown to be an alternative electron acceptor to azo compounds and must therefore be excluded during enzymatic dye reduction. Biotransformation of the azo dyes Flame Orange and Ruby Red was studied in more detail using UV-visible spectroscopy, high-performance liquid chromatography, and mass spectrometry (MS). Reduction of the azo bonds leads to cleavage of the dyes resulting in the cleavage product 2-amino-1,3 dimethylimidazolium and N∼1∼,N∼1∼-dimethyl-1,4-benzenediamine for Ruby Red, while only the first was detected for Flame Orange because of MS instability of the expected 1,4-benzenediamine. The azoreductase was also found to reduce vat dyes like Indigo Carmine (C.I. Acid Blue 74). Hydrogen peroxide (H2O2) as an oxidizing agent was used to reoxidize the dye into the initial form. The reduction and oxidation mechanism of Indigo Carmine was studied using UV-visible spectroscopy

Effect of Deamidation and Succinylation on Some Physicochemical and Baking Properties of Gluten

Vital wheat gluten was modified by deamidation and succinylation. Deamidation caused a progressive degradation of gliadin with concomitant increase in low molecular weight components, but glutenin was not affected. Deamidation also markedly increased the net negative charge and surface hydrophobicity of gluten, while the bread loaf volume and dough extensibility were decreased. The most significant change in physiochemical properties of gluten caused by succinylation was an increase in net negative charge. Succinylation led to a pronounced decrease in dough extensibility but no significant changes in specific loaf volume. The data indicated the importance of hydrogen bonding offered by the amide groups of gluten in the breadmaking process. Changes in molecular weight distribution and hydrophobic interaction may also affect the baking performance of gluten. Ionic interaction may be involved in dough development but is less critical in controlling the overall baking performance of gluten.link_to_subscribed_fulltex