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. 2022 Aug 12;19(16):9962.
doi: 10.3390/ijerph19169962.

Biodegradation of Azo Dye Methyl Red by Pseudomonas aeruginosa: Optimization of Process Conditions

Muhammad Ikram  1 , Mohammad Naeem  1 , Muhammad Zahoor  2 , Abdur Rahim  3 , Marlia Mohd Hanafiah  4   5 , Adeleke Abdulrahman Oyekanmi  4 , Abdul Bari Shah  6 , Mater H Mahnashi  7 , Amer Al Ali  8 , Naif A Jalal  9 , Farkad Bantun  9 , Abdul Sadiq  10
Affiliations

Biodegradation of Azo Dye Methyl Red by Pseudomonas aeruginosa: Optimization of Process Conditions

Muhammad Ikram et al. Int J Environ Res Public Health. .

Abstract

Water pollution due to textile dyes is a serious threat to every life form. Bacteria can degrade and detoxify toxic dyes present in textile effluents and wastewater. The present study aimed to evaluate the degradation potential of eleven bacterial strains for azo dye methyl red. The optimum degradation efficiency was obtained using P. aeruginosa. It was found from initial screening results that P. aeruginosa is the most potent strain with 81.49% degradation activity and hence it was subsequently used in other degradation experiments. To optimize the degradation conditions, a number of experiments were conducted where only one variable was varied at a time and where maximum degradation was observed at 20 ppm dye concentration, 1666.67 mg/L glucose concentration, 666.66 mg/L sodium chloride concentration, pH 9, temperature 40 °C, 1000 mg/L urea concentration, 3 days incubation period, and 66.66 mg/L hydroquinone (redox mediator). The interactive effect of pH, incubation time, temperature, and dye concentration in a second-order quadratic optimization of process conditions was found to further enhance the biodegradation efficiency of P. aeruginosa by 88.37%. The metabolites of the aliquot mixture of the optimized conditions were analyzed using Fourier transform infrared (FTIR), GC-MS, proton, and carbon 13 Nuclear Magnetic Resonance (NMR) spectroscopic techniques. FTIR results confirmed the reduction of the azo bond of methyl red. The Gas Chromatography-Mass Spectrometry (GC-MS) results revealed that the degraded dye contains benzoic acid and o-xylene as the predominant constituents. Even benzoic acid was isolated from the silica gel column and identified by 1H and 13C NMR spectroscopy. These results indicated that P. aeruginosa can be utilized as an efficient strain for the detoxification and remediation of industrial wastewater containing methyl red and other azo dyes.

Keywords: P. aeruginosa; biodegradation; methyl red; textile dyes; wastewater.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript or in the decision to publish the results.

Figures

Figure 1
Figure 1
Percent degradation of methyl red by different bacteria.
Figure 2
Figure 2
Dye concentration impact on % degradation.
Figure 3
Figure 3
pH effect on % degradation of methyl red dye.
Figure 4
Figure 4
Temperature impact on % degradation of methyl red dye.
Figure 5
Figure 5
Incubation time (days) impact on % degradation.
Figure 6
Figure 6
Glucose concentration and its impact on percent degradation of methyl red.
Figure 7
Figure 7
Urea concentration effect on methyl red % degradation.
Figure 8
Figure 8
Effect of sodium chloride (mg/L) on dye % degradation.
Figure 9
Figure 9
Redox mediators impact on (66.66 mg/L) on methyl red % degradation.
Figure 10
Figure 10
Methyl red dye (a) before treatment and (b) after treatment of P. aeruginosa.
Figure 11
Figure 11
Response surface plot for the interaction of (a) pH and incubation time (b) pH and temperature (c) incubation time and dye concentration (d) temperature and dye concentration for the biodegradation of methyl red using P. aeruginosa.
Figure 11
Figure 11
Response surface plot for the interaction of (a) pH and incubation time (b) pH and temperature (c) incubation time and dye concentration (d) temperature and dye concentration for the biodegradation of methyl red using P. aeruginosa.
Figure 12
Figure 12
(a) FTIR spectra of methyl red before biodegradation (b) FTIR spectra of methyl red dye after P. aeruginosa degradation.
Figure 13
Figure 13
(a) GC chromatogram of methyl red after bacterial degradation; (b,c) GC–MS chromatograms of two important metabolites.
Figure 14
Figure 14
TLC profiling under UV light.
Figure 15
Figure 15
1H NMR of the methyl red.
Figure 16
Figure 16
13C NMR of methyl red dye.
Figure 17
Figure 17
1H NMR of metabolite.
Figure 18
Figure 18
13C NMR of the metabolite.
Figure 19
Figure 19
Chemical structure of an isolated metabolite (benzoic acid).
Figure 20
Figure 20
Proposed degradation mechanism of methyl red by P. aeruginosa.
See this image and copyright information in PMC

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