Optimization of spore laccase production by Bacillus amyloliquefaciens isolated from wastewater and its potential in green biodecolorization of synthetic textile dyes

Abstract

The spore laccase enzyme production by B. amyloliquefaciens was optimized. It was characterized and tested for its textile dye decolorization potential. LB medium was found to be the most promising growth medium with addition of glucose (1–2%), yeast extract (0.1%), FeCl₃ (0.01 mM) and MnCl₂ (0.001 mM). The optimum spore laccase production was at pH 8, 30 °C, 1:5 medium to air ratio, 2% inoculum size and 7 days incubation. The characterization study of the enzyme showed the maximum activity at 60 °C and pH 6–7.5. It was induced by Ca⁺², Mg⁺², Fe⁺³, Zn⁺², Cu⁺² and Na⁺ at 1 mM concentration. Also, it was stable in the presence of methanol, ethanol, acetone and chloroform. In addition, it enhanced about 34% by 5 mM H₂O₂ and it was nearly stable at 10–20 mM H₂O₂. Furthermore, mediators such as ABTS, syrengaldazine and 2, 6 dimethyl phenol enhanced the spore laccase activity. The spore laccase enzyme efficiently decolorized direct red 81 and acid black 24 after 24 h. Phytotoxicity of the direct red 81 solution after decolorization by tested spore laccase was lower than that of the untreated dye solution. Finally, this study added a promising spore laccase candidate for ecofriendly and cost-effective dye wastewater bio-decolorization.

Keywords:

• Bacillus
• characterization
• dye decolorization
• phytotoxicity
• production
• spore laccase

Acknowledgements

The authors thank and appreciate National Water Research Center, National Research Center and Faculty of Science, Al-Azhar University of Egypt for their financial, technical and moral support.

Disclosure statement

No potential conflict of interest was reported by the authors.