The effect of pH and some nutrients starvation on biodegradation of azo dyes (Orange II and Direct Blue 71) by
Pseudomonas
sp. was investigated. Highest percentage decolourization values of 56.50% and 45.20% were obtained at pH 7.0 and 6.5 for Orange II and Direct Blue 71 respectively. Rate of decolourization decreased with increasing concentration of nitrate (sodium nitrate) or sulphate (magnesium sulphate heptahydrate). Highest percentage decolourization (79.29% for Orange II and 72.38% for Direct Blue 71) was obtained in positive controls (no nitrate added). Corresponding values for sulphate-limited conditions were 76.50% for Orange II and 78.24% for Direct Blue 71 in positive controls (no sulphate added). The nitrogen of the generated aromatic amines provided the sole source of nitrogen in positive controls. Desulphonation of the aromatic moiety provided the sole source of sulphur in the positive control medium. The study shows that detoxification of ecosystems contaminated with azo dyes are enhanced under nitrate and sulphate-limited conditions. @JASEM
