In this paper, the microbial degradation of Methyl Red (MR) was investigated by novel isolated bacteria S1 and K1 from wastewater effluent. Based on morphological, biochemical and molecular methods, strain S1 belonged to the Staphylococcus schleiferi subsp. coagulans GA 211 with 92.67% similarity (accession number MT573965) and strain K1 belonged to the Klebsiella michiganensis W14 with 99.85% similarity (accession number MT572941). To the best of our knowledge, this is the first report of dye degradation activity of these bacteria. The Taguchi Statistical Method (TSM) was used to optimize the experimental conditions. Taguchi’s L18 orthogonal array (OA) was performed and the results were used to calculate signal-to-noise (S/N) ratios. According to S/N ratios, it was discovered that optimum experimental conditions is at pH 8, temperature 40°C, initial dye concentration 50 mg/l, carbon source glucose, rpm 75, inoculum 3% v/v and strain S1. Analyzing the results of the biodegradation assay by Minitab 19 statistical software, it was found that rpm and temperature are most and less effective in the MR biodegradation assay, respectively. Significant changes in the HPLC and UV-Vis spectrum of samples of strain S1 before and after biodegradation assay, confirmed the complete biodegradation of MR by S1 strain.

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