Biodegradation of remazol black B in an anaerobic/aerobic condition using bacterial consortium in a stirred tank reactor

Abstract

Degradation of a sulphonated azo dye, Remazol Black B (RBB) was conducted in batch fermentation under sequential anaerobic and aerobic conditions in a 2 L bioreactor. Initially, consortium of strains C l and L I 7 was used to decolourise and reduce RBB anaerobically followed by AI and F5 strains to further degrade the reduced products under aerobic condition. Batch fermentation was conducted in a 2 L bioreactor (1.5 L working volume) with constant agitation at 200 rpm. Under anaerobic condition, RBB was reduced thus decolourised through the reduction of the N=N bond. Anaerobic condition was provided by sparging the culture with nitrogen gas continuously. Previously optimized parameters such as dye and nutrient concentration, inoculum size, temperature and pH were used. Complete decolourisation in the bioreactor was observed within 45 minutes. Decolourisation was achieved in a Vt strength P5 medium (pH 7) containing 5 g/L of nutrient broth supplement, 2.5 g/L of glucose and incubated at 45°C. Subsequent to anaerobic decolourisation, two intermediates were thought to be formed, p-Base and triaminohydroxylnaphthalene disulphanilic acid. These products were then subjected to aerobic incubation for 13 days at for mineralization of the reduced products. High Performance Liquid Chromatography (HPLC) analyses showed the formation of sulphanilic acid (SA) as a possible degradation product of p-Base. Sulphanilic acid could then be further biotransformed to other intermediates due to the disappearance of the SA peak with time.