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สารฮิ วมิ กช่วยเพิ่ มความสามารถการลดสี ... 206 The Journal of the Royal Institute of Thailand Vol. 37 No. 1 Jan.-Mar. 2012 FIG.3 Anaerobic reduction of sulfonat- ed azo dyes in the presence of different concentrations of AQDS by whole cells of Paenibacillus sp. strain A5. The cells of strain A5 were grown aerobically in a minimal medium with glucose (5mM). When cell reached the lated-ex- ponential growth phase, cells were har- vested by centrifugation and resuspend- ed anaerobically in Na-K phosphate buffer (pH 7.5; 50 mM). This cell sus - pension (protein content, 0.09 g l -1 ) was completely filled into cultured tubes (10 ml). The oxygen-free reaction mixtures contained sulfonated azo dyes (0.1 mM), glucose (5 mM), and different concentration of AQDS. The decolorization of the sulfonated azo dyes was measured spectrophotometrically at λ max of each azo dye. Comparison of the azo reductase activities in different cellular components of Paenibacillus sp. strain A5 with different industrially sulfonated azo dyes In the present study it was attempted to determine the location of the enzyme system(s) responsible for the reduction of sulfonated azo dyes by Paenibacillus sp. strain A5 in the presence of AQDS. Therefore, azo reductase activities of cellular membrane and cytoplasm of strain A5 were compared in the presence of AQDS (0.05 mM) in reaction mixtures. Thus, it was found that the majority of AQDS-dependent azo reductases activities present in membrane fraction of strain A5 (Table 2). Up to the present, the most generally accepted hypothesis for bacterial reduction of azo dyes is that many bacterial cells possess a rather unspecific cytoplasmic azo reductases which transfers electrons via soluble or bound-flavins to the azo dyes (45, 56). The involvement of different low molecular weight redox mediators (e.g., flavins and quinones) in the bacterial reduction of azo dyes have been repeatedly suggested (14, 26, 29, 42, 43, 50). In this manuscript, it was also attempted for the first time to perform the comparison of the effects of both flavin-type (FAD) and quinoid-type mediator (AQDS) on azo reductase activities present in different cellular components.