Abstract
Catalase is an effective biocatalyst to degrade hydrogen peroxide to water and oxygen that can serve in textile effluent treatment to remove residual H2O2. Thermostable catalases are needed to withstand both the high temperature and pH of textile wastewater. We have cloned the Mn-containing catalase gene ACS24898.1 from Geobacillus sp. WCH70, which originated from thermophilic organisms, and expressed it in Escherichia coli in activated form. The recombinant protein has been purified to homogeneity and identified to be a new homo-hexamer Mn-containing catalase. The native molecular mass of the catalase has been measured to be 138 kDa by size-exclusion chromatography. The new enzyme has optimum catalyzed activity at pH 9.0 and a temperature of 75 °C. It is thermostable up to 70 °C for 8 h incubation and maintains 80% and 50% activity, respectively, at 80 °C after 5 h and 90 °C after 1 h. At 75 °C and pH 9.0, the Km is 67.26 mM for substrate H2O2 and the rate of reaction at H2O2 saturation, Vmax, is 75,300 U/mg. The thermophilic and alkaline preferred properties of this new Mn-catalase are valuable features in textile wastewater treatment.
Highlights
Enzyme catalase (EC 1.11.1.6) mostly exists in aerobic living organisms
Its main function is to catalytically decompose hydrogen peroxide (H2 O2 ) to water and oxygen in order to protect the cells from oxidative challenging by over-produced H2 O2 [1,2]
The total length of gene sequence ACS24898.1 is 570 bp, and the encoded protein contains 189 sequences of selected manganese catalases from bacterial or archaea are obtained from PeroxiBase
Summary
Enzyme catalase (EC 1.11.1.6) mostly exists in aerobic living organisms. Its main function is to catalytically decompose hydrogen peroxide (H2 O2 ) to water and oxygen in order to protect the cells from oxidative challenging by over-produced H2 O2 [1,2]. Catalases have potential to be industrial enzymes in environmental protection for removing H2 O2 containing effluents [3,4]. H2 O2 is widely used for bleaching. It is essential to remove the residual H2 O2 from industrial waste after the reactions. The removal of residual H2 O2 can be done by extensive washing (100 L of water/1 kg of textiles) or using chemicals in the textile industry, which could cause further downstream problems [6]. In the textile bleaching industry, the wastewater temperature could be more than 60 ◦ C [9]. There is need for thermostable catalases as industrial enzymes in the application of removing H2 O2 from waste. One of the approaches will be to discover thermostable catalases from natural sources and to express them in expressing host cells
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