A novel laccase from thermoalkaliphilic bacterium Caldalkalibacillus thermarum strain TA2.A1 able to catalyze dimerization of a lignin model compound

Abstract

In the present study, the gene encoding a multicopper oxidase, more precisely a laccase from the thermoalkaliphilic aerobic bacterium Caldalkalibacillus thermarum strain TA2.A1 (CtLac), was cloned and expressed in Escherichia coli. CtLac is a monomeric protein with a molecular weight of 57 kDa as determined by native polyacrylamide gel electrophoresis. The optimum pH and temperature for 2,6-dimethoxyphenol (2,6-DMP) oxidation were 8.0 and 70 °C, respectively. The kinetic constants K and k for 2,6-DMP were of 200 μM and 23 s, respectively. The enzyme was highly thermostable at 80 °C and retained more than 80% of its activity after 24 h preincubation under thermoalkaliphilic conditions. Remarkably, it showed a half-life of about 12 h at 90 °C. The enzyme activity was significantly enhanced by Cu and Mn and was not affected in the presence of most of the other metal ions. CtLac activity was stimulated in the presence of halides, organic solvents, and surfactants. Furthermore, the activity of CtLac on a dimeric lignin model compound, guaiacylglycerol-β-guaiacyl ether (GGGE) was investigated. Liquid chromatography-mass spectrometry analysis indicated that CtLac catalyzes dimerization of GGGE to form a C5-C5 biphenyl tetramer. The stability and activity of CtLac characterized herein under thermoalkaliphilic conditions make it a highly suitable biocatalyst for various biotechnological and industrial applications.

Characterization of a Novel Fe2+ Activated Non-Blue Laccase from Methylobacterium extorquens

“…The blockage of the substrate pathway or the transfer of electrons at the T1 site leads to an inhibition in enzyme activity [ 44 ]. Increased laccase activity in the presence of some metal ions, especially copper, has been observed for most laccases, and this can be interpreted as Cu 2+ filling the type one Copper binding site [ 18 , 27 , 45 ].…”

Biotechnological potential of fungi and bacteria with ligninolytic activity (mini-review)

“…In the Table the most perspective strains are listed. As an example, gene encoding a laccase from a thermophilic aerobic bacteria Caldalkalibacillus thermarum TA2.A1 was cloned and expressed in E. coli [32]. It was found that laccase from this strain was monomeric protein with a molecular weight of 57 kDa.…”

Extremophilic Oxidoreductases for the Industry: Five Successful Examples With Promising Projections

“…2.9 retained 80% of its activity after 16 h at 70 • C and after 6 h at 80 • C (Navas et al, 2019). In addition, a novel laccase from the thermoalkaliphilic bacterium Caldalkalibacillus thermarum strain TA2.A1 showed optimum activity at alkaline pH 8.0 and 70 • C, with a half-life of 12 h at 90 • C, pH 8.0 and 6 h at 90 • C, pH 9.0 (Ghatge et al, 2018). Halophilic laccases are also very attractive for biotechnological applications, two examples are a highly thermostable salt/solvent-tolerant laccase from the halophilic archaeon Haloferax volcanii (Uthandi et al, 2010) and the extracellular laccase produced by the halophilic bacterium Aquisalibacillus elongatus (Rezaie et al, 2017).…”