Biodecolorization of textile azo dye using Bacillus sp. strain CH12 isolated from alkaline lake

Graphical abstract

Highlights

• •

  Bacillus sp. strain CH12 is a potential candidate for dye removal.

• •

  Strain CH12 needs alkaline pH (9–10) to bring complete dye removal efficiency.

• •

  Organic carbon and nitrogen supplements enhance dye decolorization efficiency.

• •

  Sodium nitrite and sodium nitrate lead to lower decolorization efficiency.

• •

  Under oxygen tension conditions, dye can be used as a final electron accepter.

Abstract

Textile azo dye decolorizing bacteria were isolated from alkaline Lakes Abaya and Chamo using Reactive Red 239 (RR239) dye. Through subsequent screening process, strain CH12 was selected to investigate the effects of nutrient supplement, DO, pH, temperature, dye concentration and types on decolorization. Based on 16S rRNA gene sequence analysis, strain CH12 was identified as Bacillus sp. Decolorization efficiencies were significantly enhanced with carbon (≥98%) and organic nitrogen (∼100%) supplements. Complete decolorization was also observed under anoxic and anaerobic conditions, and at the temperature of 30 °C and the pH of 10. However, the azo dye decolorization efficiency of strain CH12 was significantly reduced when NaNO ₃ (1–8%) was supplemented or under aerobic culturing condition (≤6%), indicating that RR239 was less preferred electron acceptor. Overall, strain CH12 can be a promising candidate for decolorization applications due to its potential to effectively decolorize higher RR239 concentrations (50−250 mg/L) and six additional dyes.