Biotransformation of Food Dyes by Human Intestinal Bacteria (Streptococcus faecalis, Eschericia coli)

Biotransformation of food dyes (Tartrazine and Quinoline yellow) by Streptococcus faecalis and Escherichia coli isolated from human intestinal microflora was investigated. Decolourisation of the media containing the dyes was used as an index of biotransformation. Biotransformation was higher under aerobic than under anaerobic conditions. The results obtained were attributed to the organisms cytosolic flavin-dependent reductases and redox equivalents generated by metabolism of soluble starch which transfer electrons to the chromophoric group of the dyes. The potential health risk of the resulting colourless metabolites (aromatic amines) is under investigation. @JASE

Influence of chemical structures on biodegradation of azo dyes by Pseudomonas sp

No Abstract. Global Journal of Environmental Sciences Vol. 5(1) 2006: 19-2

Effect of pH and nutrient starvation on biodegradation of azo dyes by Pseudomonas sp

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. @JASE

Toxic Effect Of Azo Dyes On Nitrite-N Utilization By Nitrobacter

The toxicity of five azo dyes (toxicants) on Nitrobacter was investigated. The index for toxicity was inhibition of rate of nitrite-N utilization. The rate of nitrite-N utilization decreased with increase in concentration of each toxicant at specific exposure time. However, stimulation of utilization was obtained at low concentrations and short exposure time for two of the dyes. This was attributed to hyperactivity. The median effective concentration50 (EC50) values increased with increase in exposure time for each toxicant. This was attributed to acclimatization and/or detoxification. Inhibition was attributed to any/or all of the following factors: molecular size, impurities in the toxicants and dye content. KEY WORDS: Toxicity, Azo dyes, Nitrobacter, hyperactivity, acclimatization Global Journal of Environmental Sciences Vol.4(1) 2005: 47-5

Biodegradation of Azo dyes by immobilized and free cells of Pseudomonas sp.under fed-batch conditions

No Abstract. Global Journal of Environmental Sciences Vol. 5(1) 2006: 1-

Quantal Response Of Freshwater Shrimp (Desmocaris trispinosa) To Toxicity Of Azo Dyes

The quantal-response of freshwater shrimp (Desmocaris trispinosa) to the toxicity of five azo dyes was studied. Generally, increase in percentage mortality of the organisms was obtained with increases in concentration of the toxicants and exposure time. The median lethal concentration50 (LC50) and median lethal concentration50 (LC50) values were obtained from the concentration-mortality and time-mortality probit graphs, respectively. Based on the LC50 and LT50 values, the dyes were ranked in order of toxicity: Mordant Black 11>Acid Orange 10>Direct Red 28>Direct Orange 31>Direct Red 23. Differences in quantal effect of the toxicants was attributed to their molecular weight, dye content and/or impaired oxygen transfer through the respiratory apparatus of the organisms due to adsorption of the dye molecules on their gill surface. Evidence of bioaccumulation of the toxicants in guts and tissues of the shrimps was obtained and its implication to human health was discussed. KEY WORDS: Toxicity, azo dyes, Desmocaris trispinosa, quantal response, bioaccumulation Global Journal of Environmental Sciences Vol.4(1) 2005: 41-4