Cloning, expression, and characterization of a thermostable and pH-stable laccase from Klebsiella pneumoniae and its application to dye decolorization

• DOI: 10.1016/j.procbio.2016.11.015
• Publication Date: 2016-11-30T06:56:43Z
• Authors: Yihan Liu; Lin Huang; Wei Guo; Leibo Jia; Yu Fu; Shuang Gui; Fuping Lu
• Keywords: Thermostability; ABTS; Thermal Stability

Abstract A thermostable and pH-stable laccase from Klebsiella pneumoniae was cloned and expressed in Escherichia coli. The recombinant laccase (rLac) achieved a specific activity of 7.12 U/mg after purification by Ni-affinity chromatography. Optimal enzyme activity was observed at pH 4.0 and 35 °C for 2,2′-azino-bis (3-ethylbenzthiazoline sulfonic acid) (ABTS) oxidization and pH 8.0 and 70 °C for 2,6-dimethoxyphenol (2,6-DMP) oxidization. Thermostability and pH stability studies showed that the rLac was stable over the range of 30–70 °C and pH 5.0–9.0 using 2,6-DMP as substrate. Circular dichroism analysis suggested that the secondary structure of the rLac mainly consisted of α-helix that played a vital role in maintaining laccase activity and revealed the potential mechanisms for the changes in laccase activity under varying pHs (3.0–11.0) and temperatures (20–90 °C). Finally, the rLac could decolorize the tested dyes with high decolorization efficiency.