Biochemical and Structural Properties of a High-Temperature-Active Laccase from Bacillus pumilus and Its Application in the Decolorization of Food Dyes

A novel laccase gene isolated from Bacillus pumilus TCCC 11568 was expressed, and the recombinant laccase (rLAC) displayed maximal activity at 80 degrees C and at pH 6.0 against ABTS. rLAC maintained its structural integrity at a high temperature (355 K) compared to its tertiary structure at a low temperature (325 K), except for some minor adjustments of certain loops. However, those adjustments were presumed to be responsible for the formation of a more open access aisle that facilitated the binding of ABTS in the active site, resulting in a shorter distance between the catalytic residue and the elevated binding energy. Additionally, rLAC showed good thermostability (<= 70 degrees C) and pH stability over a wide range (3.0-10.0), and displayed high efficiency in decolorizing azo dyes that are applicable to the food industry. This work will improve our knowledge on the relationship of structure-function for thermophilic laccase, and provide a candidate for dye effluent treatment in the food industry.