Bioremediation of reactive blue 19 dye by laccase-producing Serratia marcescens AY4 strain

Abstract

Laccase-producing bacteria are bioinspired tools for the degradation of textile dyes. Five laccase-producing bacterial strains were isolated from industrial effluent, and a potential bacterial strain, AY4, was identified by 16S rRNA gene amplification as Serratia marcescens AY4 (OR625080). It decolorized 96 % (0.98 mg L−1 h−1) of RB-19 (100 mg L−1) at 37 °C and 7.0 pH with 1 mM guaiacol and 2 mM CuSO4. Machine learning modeling (predictive models: decision trees, random forest, XGBoost, K-nearest neighbors and support vector) showed that the incubation period played a more decisive role in decolorization than the dye concentration, and the removal rate (96.4 %) was statistically significant (p < 0.05) after 96 h of incubation. XGBoost outperformed on the training dataset (R² of 1.00 and an RMSE of 0.0) and showed comparable results on the test dataset. It was selected for its consistent and robust performance. UV–vis and FTIR analysis confirmed the decolorization and three metabolites were identified by GC-MS analysis as phenol-4,4-(1-methyl ethylidene)bis- (retention time RT, 24.110; m/z, 228.291), bis(2-ethylhexyl) phthalate (RT, 29.59; m/z, 390.564), and 2,4-Di-tert-butylphenol (RT, 13.34 and m/z: 206.1) of Reactive Blue 19. The microbial toxicity study on Serratia marcescens and E. coli confirmed nontoxic effect of degraded RB-19 metabolites and indicates promising degradation potential of S. marcescens strain AY4 to successfully remediate RB-19 dye ecologically sustainably. This outcome promotes an eco-friendly and sustainable approach to eliminating the contaminants from textile wastewater.