Biodegradation of Methylene Blue Using a Novel Lignin Peroxidase Enzyme Producing Bacteria, Named <i>Bacillus</i> sp. React3, as a Promising Candidate for Dye-Contaminated Wastewater Treatment

The emission of methylene blue (MB) from common industries causes risks to human health by making clean drinking water unavailable and hampering environmental safety. A biological approach offering a more cost-efficient and sustainable alternative solution has been studied and demonstrated to be significantly effective for the removal of MB using promising microbial isolates. Therefore, this study targeted bacterial candidates, namely Bacillus sp. React3, isolated from soil with the potential to decolorize MB. The phenogenic identification of strain React3 was performed by 16S rRNA sequencing, showing a similarity of 98.86% to Bacillus velezensis CR-502T. The ability of this bacterial strain to decolorize MB was proven through both the lignin peroxidase efficiency and accumulation in the biomass of the living cells. MB removal was determined by the reduction in the maximum absorption at a wavelength of 665 nm, which was observed to be up to 99.5% after 48 h of incubation. The optimal conditions for the MB degradation of strain React3 were pH 7, 35 °C, static, 4% inoculum, and 1000 mg/L of MB, with tryptone as a carbon source and yeast extract as a nitrogen source