부산대학교 도서관

Azo dyes are widely used in the food, pharmaceutical, paper, and textile industries. Some azo dyes are known to produce carcinogenic compounds upon reductive cleavage of the azo bond (N =N) by intestinal flora. There is not much information available on the effect of these dyes on the physiology of the gut microflora as well as their kinetics of reduction in different environments. The azoreductase activity of Enterococcus faecalis, an important opportunistic intestinal pathogen, was tested using the azo dyes Methyl Red, Direct Blue 15 and tartrazine under the following conditions: a complex supplemented brain heart infusion (BHIS) medium under aerobic and anaerobic conditions, a simple phosphate-buffered saline glucose (PBSG) medium under anaerobic conditions, and cell extracts using NADH and NADPH as electron donors, under aerobic conditions. The kinetics of reduction in all these conditions was determined. The effect of high and low concentrations of each dye on the growth of E. faecalis was also tested. Our results show that the sulfonated azo dye tartrazine was completely reduced extracellularly in BHIS under aerobic and anaerobic conditions while the other sulfonated azo dye, Direct Blue 15 was completely reduced only under anaerobic conditions. The non-polar azo dye, Methyl Red was also completely reduced, with the highest rate of reduction in both conditions. The generation time of E. faecalis in the presence of high concentration of tartrazine was significantly lower than the control, while the generation time was unaffected in the presence of low and high concentrations of Methyl Red, Direct Blue 15 and 20 µM tartrazine. Our results suggest that the metabolism of different azo dyes by E. faecalis depends on the physiochemical properties of the azo dyes and the conditions of the surrounding environment in the presence of actively dividing cells. [ABSTRACT FROM AUTHOR]