Role of Bacterial-Fungal Consortium for Enhancement in the Degradation of Industrial Dyes

Abstract

Background: The presence of anthraquinone (Disperse blue 64) and azodyes (Acid yellow 17) in a waterbody are considered among the most dangerous pollutants.

Methods: In this study, two different isolated microbes, bacterium and fungus, were individually and as a co-culture applied for the degradation of Disperse Blue 64 (DB 64) and Acid Yellow 17 (AY 17) dyes. The isolates were genetically identified based upon 16S (for bacteria) and ITS/5.8S (for fungus) rRNA genes sequences as Pseudomoans aeruginosa and Aspergillus flavus, respectively.

Results: The fungal/bacterial consortium exhibited a higher percentage of dyes degradation than the individual strains, even at a high concentration of 300 mg/L. Azoreductase could be identified as the main catabolic enzyme and the consortium could induce azoreductase enzyme in the presence of both dyes. However, the specific substrate which achieved the highest azoreductase specific activity was Methyl red (MR) (3.5 U/mg protein). The tentatively proposed metabolites that were detected by HPLC/MS suggested that the reduction process catalyzed the degradation of dyes. The metabolites produced by the action consortium on two dyes were safe on Vicia faba and Triticum vulgaris germination and health of seedlings. Toxicity of the dyes and their degradation products on the plant was different according to the type and chemistry of these compounds as well as the type of irrigated seeds.

Conclusion: We submit that the effective microbial degradation of DB64 and AY17 dyes will lead to safer metabolic products.

Keywords: 16S and ITS/5.8S rRNA genes sequences; Aspergillus; HPLC/MS; Pseudomonas; acid yellow 17; disperse blue 64.

Fig. (1a).

Phylogenetic relationship between the strain AUMC B-171 and other 16S rRNA gene sequences of published Pseudomonas spp.

Fig. (1b)

Phylogenetic relationship between the strain AUMC-10515 and other ITS rDNA sequences of published Aspergillus spp.

Fig. (2)

Effect of initial dye concentration on the degradation percentage of DB 64 (a) and AY 17 (b) at the static condition for bacterial isolate AUMC B-171, fungal isolate AUMC-10515 and consortium. Error bars represent the standard deviation (SD±) of three replications.a; significant increase (P < 0.05) in percentage of degradation of AUMC-10515 compared to AUMC-B-171. a,b; a significant increase (P < 0.05) in percentage of degradation of consortium compared to the AUMC-B-171 and AUMC-10515.

Fig. (3)

Effect of pH (a) and temperature (b) on the azoreductase activity (U/min) in strains AUMC B-171 and consortium when the MR was a specific substrate 50 µM at 430 nm. Error bars represent the standard deviation (SD±) of three replications.

Fig. (4)

A Lineweaver-Burk plot for determining the kinetic parameters of azoreductase in AUMC B-171 (a) and consortium (b) at pH 7.5 and Temperature 40°C.

Fig. (5)

The effect of dist. H₂O (-ve control), DB 64 and AY 17 (+ve control) and dyes metabolites produced from AUMC B-171, AUMC-10515 and Consortium on the Triticum vulgaris and Vicia faba seedling shoot and root lengths. (A higher resolution / colour version of this figure is available in the electronic copy of the article).