| Abstract |
Azo dyes resemble the largest group of synthetic dyes used in many industries including textile and cosmetics industries. The release of untreated effluents of these industries in the environment directly is a serious problem due to the recalcitrant nature of these dyes and their byproducts. So, searching for new strategies can be used in the treatment of different wastewater of azo dyes will be a good solution for the previous problems.
The results of this study can be summarized as following:
• 103 streptomycetes isolates were isolated from different environments including soils and water (marine water).
• The best isolates which give high degradation are (S10, S12, A5 and A7).
• The ability of isolates to decolorize different concentrations of the different dyes was studied and the best dye concentration was 0.3 gm/l giving the highest biodegradation percent.
• The most isolates had high biodegradation activity (A7) were subjected to morphological, physiological, biochemical and molecular identification.
• Production of extracellular laccase by the two Streptomyces isolates (A5 and A7) was measured and the isolate (A7) showed the highest specific activity 5.96 U/mg.
• The molecular identification confirmed the isolated (A7) as Streptomyces albidoflavus 3MGH with accession number #MW185782.1.
• The effect of different incubation times on the biodegradation activity on different Azo dyes (Mono, Di, and Tri azo dye) by Streptomyces albidoflavus 3MGH was studied. And the results showed that the best biodegradation was after 5 days was 56.62%, 58.75%, and 53.49% in Mono, Di, and Tri azo dye respectively.
• The effect of different incubation temperatures on the biodegradation activity on different Azo dyes by Streptomyces albidoflavus 3MGH was studied. And the results showed that the best biodegradation was at 35°C at which the biodegradation was 59.87%, 61.71%, and 58.2% in Mono, Di, and Tri azo dye respectively.
• The effect of different PH on the biodegradation activity on different Azo dyes as Mono Azo dyes by Streptomyces albidoflavus 3MGH was studied and the best biodegradation was at PH 6.0 at which the biodegradation was 69.1%, 68.52%, and 67.3% in Mono, Di, and Tri azo dye respectively.
• The effect of different nitrogen sources on the biodegradation activity on different Azo dyes by Streptomyces albidoflavus 3MGH was studied and the results showed that Peptone and Beef extract was the best organic N- sources increasing Azo dye biodegradation significantly (82.04%, 80.91%, and 79.9% in Mono, Di, and Tri azo dye), (74.51%, 85.12%, and 82.48% in Mono, Di, and Tri azo dye) respectively.
• The effect of different C- sources on the biodegradation activity on different Azo dyes by Streptomyces albidoflavus 3MGH was studied and the results showed that Sucrose was the best C- sources increasing Azo dye biodegradation significantly than other sources giving 89.79%, 85.06%, and 83.44% in Mono, Di, and Tri azo dye respectively.
• The results of FTIR spectra had confirmed the biodegradation of different Azo dyes by the action of Streptomyces albidoflavus 3MGH. The peaks appeared in control have completely disappeared, which provides evidence of rupture at azo bond sit, which explains decolorization occurs in the dye’s solutions due to the action of Streptomyces albidoflavus 3MGH.
• From FTIR chart of mono azo dye, 18 peaks of the (Reactive Orange 122) were transformed into 9 peaks after Streptomyces albidoflavus 3MGH incubation. Likewise, the di azo dye the peaks were reduced from 12 to 7 after incubation. Finally, the 9 peaks that appeared in the FTIR chart for the control tri azo dye (Direct Black 38) were reduced to only 6 in the sample that was incubated with Streptomyces albidoflavus 3MGH.
• From the results obtained from the TOC test for the three dyes used in this study, it was found that there is a very large reduction in TOC value after Streptomyces albidoflavus 3MGH action. The highest removal rate was with mono azo dye, di azo was the next, and the test showed that the lowest value of the TOC removal ratio was that of the tri azo dye. This can be explained by the chemical nature of the dyes. In general, however, the removal ratio for all three dyes is very significant.
• From the color Analysis test the results obtained of the three solutions of dyes used in this study before and after incubation with Streptomyces albidoflavus 3MGH at optimum conditions, the results indicate a significant decrease in the color of the solution of the mono azo dye (Reactive Orange 122) compared to the control value. Di (Direct Blue 15) and tri azo dye (Direct Black 38) also recorded good value in terms of color reduction, this generally refers to certain changes that occurred in the structures of those solutions that caused the removal of a large proportion of the coloring matter as a result of incubation with Streptomyces albidoflavus 3MGH, which was previously supported by both FTIR and TOC tests.
• All of the resulted fragmentations, which could be identified from GC-MC chromatograms, provide evidence supporting the degradation mechanisms of the dyes by the influence of Streptomyces albidoflavus 3MGH at optimum condition.
• The results obtained from HPLC chromatograms on the products of metabolites process after decolorization of the dyes under study, provided further evidence on the occurrence of fundamental changes in the chemical composition of dyes after incubation with Streptomyces albidoflavus 3MGH at optimum condition.
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