A catalase-peroxidase from a newly isolated thermoalkaliphilic Bacillus sp. with potential for the treatment of textile bleaching effluents

Abstract.

A new thermoalkaliphilic bacterium was isolated from a textile wastewater drain and identified as a new Bacillus sp. (Bacillus SF). Because of its high pH stability and thermostability, a catalase-peroxidase (CP) from this strain has potential for the treatment of textile bleaching effluents. The CP from Bacillus SF was purified to more than 70.3-fold homogeneity using fractionated ammonium sulfate precipitation, hydrophobic interaction, and anion-exchange and gel-filtration chromatography. The native CP had a molecular mass of 165 kDa and was composed of two identical subunits. The isoelectric point of the protein was at pH 6.0. Peptide mass mapping using matrix-assisted laser desorption ionization–mass spectrometry showed a homology between the CP from Bacillus SF and the CP from Bacillus stearothermophilus. The apparent K _m value of the catalase activity for H₂O₂ was 2.6 mM and the k _cat value was 11,475 s^–1. The enzyme showed high catalase activity and an appreciable peroxidase activity with guaiacol and o-dianisidine. The enzyme was stable at high pH, with a half-life of 104 h at pH 10 and 25°C and 14 h at 50°C. The enzyme was inhibited by azide and cyanide, in a competitive manner, but not by the catalase-specific inhibitor 3-amino-1,2,4-triazole.