Optimization and enhancement of textile reactive Remazol black B decolorization and detoxification by environmentally isolated pH tolerant Pseudomonas aeruginosa KY284155

Abstract

Azo dyes are complex derivatives of diazene used in food and textile manufacture. They are highly recalcitrant compounds, and account for severe environmental and health problems. Different strains of Pseudomonas species were isolated from textile wastewater effluents. The bioconversion of Remazol black B (a commonly used water soluble dye) by Pseudomonas aeruginosa was observed in static conditions. The bio-decolorization process was optimized by a multi factorial Plackett–Burman experimental design. Decolorization of 200 mg L−1 reached 100% in 32 h. Interestingly, the presence of yeast extract, magnesium and iron in the culture media, highly accelerated the rate of decolorization. Moreover, one of our isolates, P. aeruginosa KY284155, was kept high degradation rates at high pH (pH = 9), which represents the pH of most textile wastewater effluents, and was able to tolerate high concentration of dye up to 500 mg L−1. In bacteria, azo-dye degradation is often initiated by reductive azo compound cleavage catalyzed by azo-reductases. Three genes encoding azo-reductases, paazoR1, paazoR2 and paazoR3, could be identified in the genome of the isolated P. aeruginosa stain (B1). Bioinformatics analyses of the paazoR1, paazoR2 and paazoR3 genes reveal their prevalence and conservation in other P. aeruginosa strains. Chemical oxygen demand dramatically decreased and phyto-detoxification of the azo dye was accomplished by photocatalytic post treatment of the biodegradation products. We suggest applying combined biological photocatalytic post treatment for azo dyes on large scale, for effective, cheap decolorization and detoxification of azo-dyes, rendering them safe enough to be discharged in the environment.

Biological decolorization of azo dyes from textile wastewater effluent by Aspergillus niger

“…The results in present study was slightly similar with the results obtained by [33], reported that, the maximum decolorization of Remazol black was attained at pH 9. Although greatest azo-reductase enzyme optimum pH is 7, some alkali-thermostable azo-reductase showed maximum decolorization and best pH within variety from pH 8 to 9 [33,37]. Reactive azo dyes under alkaline condition lose hydrogen ions, which leads to the ionization of the dye, affecting…”

“…It is achievable that pH change affects the transport of dye particles crossway the cell membrane of microbes, which is reflected as the rate-limiting stage for the decolorization [6]. The results in present study was slightly similar with the results obtained by [33], reported that, the maximum decolorization of Remazol black was attained at pH 9. Although greatest azo-reductase enzyme optimum pH is 7, some alkali-thermostable azo-reductase showed maximum decolorization and best pH within variety from pH 8 to 9 [33,37].…”

“…Certain reports proved the high toxicity of azo dyes to microbes involved in bio-degradation. Toxicity is interacted to dye type, dye concentration and the active sites of azo reductase enzymes blockage by dye particle [16,33]. The toxicity of the dyes to fungal cells, especially at higher concentrations may be attributed to high molecular quantity, structural complication and the presence of inhibitory groups in the dye such as sulfonic acid [34].…”

“…its constancy and facilitating its elimination from solutions [33]. In contrast, [34]reported that decolorization of dyes at higher concentration was carried out an acidic condition, which further facilitates their better removal enzymatic or by cell wall adsorption by the fungi.…”

Kojic acid repurposing as a pancreatic lipase inhibitor and the optimization of its production from a local Aspergillus oryzae soil isolate

“…The calculated E-value magnitude of the tested factor shows its effect or its significance in affecting the response. The positive or negative sign of the E-value is indicative of its positive or negative influence on the responses [56]. All runs were performed in triplicates, and the lipase inhibitory activity was determined [49].…”