สำนักราชบัณฑิตยสภา

The Journal of the Royal Institute of Thailand Vol. 30 No. 1 Jan.-Mar. 2005 74 Humic Substance Enhanced Anaerobic Reduction of Sulfonated Azo Dyes by Paenibacillus sp. Strain A5 FIG. 4. Enzymatic reduction of AQDS to AH 2 QDS by Paenibacillus strain A5 and subsequent chemical reduction of sulfonated azo dyes by AH 2 QDS. Washed cells of Paenibacillus sp. strain A5 (0.09 g of protein l -1 ) were suspendend in 10 ml. Na-K phosphate buffer (50 mM; pH 7.5) containing glucose (5 mM) as the electron donor and AQDS (250 M) as electron acceptor. The concentration of reduced AQDS (AH 2 QDS) was determined spectrophotometrically at 450 nm. After 10 h of anaerobic incubation, cells were removed by filtration (0.2- M-pore-diameter filter). The cell-free culture supernatant was then filled into gas-tight cuvettes (final volume = 1 ml.) under anaerobic condition and anaerobic stock of each sulfonated azo dyes was added to 100 M final concentration. The cuvettes were transferred to a spectrophotometer and the decolorization of sulfonated azo dyes was determined at λ max of each azo dye. FIG. 5. Model for mechanism by which AQDS, a humic analogue stimulate sulfonated azo dyes reduction by Paenibacillus sp. strain A5 Sulfonated azo dye Sulfonated aromatic amines AH 2 QDS AQDS NAD + NADH + H + QD Glucose Oxidative products Paenibacillus sp. strain A5