An immobilised catalase peroxidase from the alkalothermophilic Bacillus SF for the treatment of textile-bleaching effluents.

A catalase peroxidase (CP) from the newly isolated Bacillus SF was used to treat textile-bleaching effluents. The enzyme was stable at high pH values and temperatures, but was more sensitive to deactivation by hydrogen peroxide than monofunctional catalases. Based on the Michaelis-Menten kinetics of the CP, a model was developed to describe its deactivation characteristics. The enzyme was immobilised on various alumina-based carrier materials with different shapes and the specific activity increased with the porosity of the carrier. The shape of the carrier had an important influence on the release of oxygen formed during the catalase reaction from the packed-bed reactor and Novalox saddles were found to be the most suitable shape. Bleaching effluent was treated in a horizontal packed-bed reactor containing 10 kg of the immobilised CP at a textile-finishing company. The treated liquid (500 l) was reused within the company for dyeing fabrics with various dyes, resulting in acceptable colour differences of below Delta E*=1.0 for all dyes.

Thermo-alkali-stable catalases from newly isolated Bacillus sp. for the treatment and recycling of textile bleaching effluents.

Three thermoalkaliphilic bacteria, which were grown at pH 9.3-10 and 60-65 degrees C were isolated out of a textile wastewater drain. The unknown micro-organisms were identified as thermoalkaliphilic Bacillus sp. Growth conditions were studied and catalase activities and stabilities compared. Catalases from Bacillus SF showed high stabilities at 60 degrees C and pH 9 (t1/2=38 h) and thus this strain was chosen for further investigations, such as electron microscopy, immobilization of catalase and hydrogen peroxide degradation studies. Degradation of hydrogen peroxide with an immobilized catalase from Bacillus SF enabled the reuse of the water for the dyeing process. In contrast, application of the free enzyme for treatment of bleaching effluents, caused interaction between the denaturated protein and the dye, resulting in reduced dye uptake, and a higher color difference of 1.3DeltaE* of dyed fabrics compared to 0.9DeltaE* when using the immobilized enzyme.

Immobilization of catalases from Bacillus SF on alumina for the treatment of textile bleaching effluents.

A catalase preparation from a newly isolated Bacillus sp. was covalently immobilized on silanized alumina using glutaraldehyde as crosslinking agent. The effect of the coupling time of the enzyme-support reaction was determined in terms of protein recovery and immobilization yield and a certain balance point was found after which the activity recovery decreased. The activity profile of the immobilized catalase at high pH and temperature was investigated. The immobilized enzyme showed higher stabilities (214 h at pH 11, 30 degrees C) at alkaline pH than the free enzyme (10 h at pH 11, 30 degrees C). The immobilized catalase was inhibited by anionic stabilizers or surfactants added to the hydrogen peroxide substrate solution.

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

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 Km 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 degrees C and 14 h at 50 degrees 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.