A feasible approach for azo-dye (methyl orange) degradation by textile effluent isolate Serratia marcescens ED1 strain for water sustainability: AST identification, degradation optimization and pathway hypothesis

Abstract

Methyl orange (MO) is a dye commonly used in the textile industry that harms aquatic life, soil and human health due to its potential as an environmental pollutant. The present study describes the dye degradation ability of Serratia marcescens strain ED1 isolated from textile effluent and characterized by 16S rRNA gene sequence analysis. The laccase property of bacterial isolate was confirmed qualitatively. The effects of various factors (pH, temperature, incubation time, and dye concentration) were evaluated using Response Surface Methodology (RSM). The maximum dye (MO) degradation was 81.02 % achieved at 37 °C temperature and 7.0 pH with 200 mg/L dye concentration after 48 h of incubation. The beef extract, ammonium nitrate and fructose supplementation showed better response during bioremediation among the different carbon and nitrogen sources. The degree of pathogenicity was confirmed through the simple plate-based method, and an antibiotic resistance profile was used to check the low-risk rate of antibiotic resistance. However, the fate and extinct of degraded MO products were analysed through UV-Vis spectroscopy, FT-IR, and GC-MS analysis to confirm the biodegradation potential of the bacterial strain ED1 and intermediate metabolites were identified to propose metabolic pathway. The phytotoxicity study on Vigna radiata L. seeds confirmed nontoxic effect of degraded MO metabolites and indicates promising degradation potential of S. marcescens strain ED1 to successfully remediate MO dye ecologically sustainably.

Keywords: 16S rRNA; AST; Laccase; Nitrogen and carbon source; Textile wastewater.

Fig. 1

A. Pure isolate of ED1 strain, B. The Isolate ED1 on MAP media plate, C. The Isolate ED1 on BAP media plate, D. Phylogenetic tree of S. marcescens based on the 16S rRNA gene sequence.

Fig. 2

Optimization of MO dye decolorization by S. marcescens isolate using different A. organic sources, B. inorganic nitrogen sources and, C. using different carbon sources, D. Decolorization of MO dye on different concentration.

Fig. 3

Regression plots of decolorization of MO dye, A. Plot represent normal plot of residuals, B. Plot the projection made by the algorithm versus the actual amount of decolorization.

Fig. 4

Response surface plots and contour plots, A. pH and temperature, B. pH and incubation time, C. MO dye concentration and pH, D. incubation time and temperature, E. the concentration of MO dye and temperature, F. MO dye concentration and incubation time. This experiment focused on the examination of two specific factors, while the remaining factors were held constant at a value of zero.

Fig. 4

Response surface plots and contour plots, A. pH and temperature, B. pH and incubation time, C. MO dye concentration and pH, D. incubation time and temperature, E. the concentration of MO dye and temperature, F. MO dye concentration and incubation time. This experiment focused on the examination of two specific factors, while the remaining factors were held constant at a value of zero.

Fig. 5

A. Observations of the UV–Vis wavelengths of MO dye both before and after 48 h of degradation, B. FTIR spectra of MO dye before and after 48 h of degradation, C. On mung beans, the toxicity profile of untreated and bacterially-treated MO dye at various concentrations (25 %, 50 %, 75 %, and 100 %).

Fig. 6

Chemical identification by GC-MS spectra, A. Chromatograms of Dimethyl Sulfoxide; Naphthalene, 2-methoxy; 2-Oxopropionamide; Dibutyl phthalate; 1,2-Benzenedicarboxylic acid, bis(2-methylpropyl) ester extracted metabolites of S. marcescens ED1 decolourized MO dye sample through GC-MS analysis, B. Chromatograms of Hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester; Heptadecane; 2-methyl, 2,3-Butanediol; Dodecane, 2-methyl extracted metabolites of S. marcescens ED1 decolourized MO dye sample through GC-MS analysis.

Fig. 6

Chemical identification by GC-MS spectra, A. Chromatograms of Dimethyl Sulfoxide; Naphthalene, 2-methoxy; 2-Oxopropionamide; Dibutyl phthalate; 1,2-Benzenedicarboxylic acid, bis(2-methylpropyl) ester extracted metabolites of S. marcescens ED1 decolourized MO dye sample through GC-MS analysis, B. Chromatograms of Hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester; Heptadecane; 2-methyl, 2,3-Butanediol; Dodecane, 2-methyl extracted metabolites of S. marcescens ED1 decolourized MO dye sample through GC-MS analysis.

Fig. 7

Proposed pathway for biodegradation of MO dye by S. marcescens ED1.