Enhanced hydrolysis of lignocellulosic biomass with doping of a highly thermostable recombinant laccase

A highly thermostable laccase from Geobacillus sp. strain WSUCFI was cloned into Escherichia coli (E. coli) using pRham N-His SUMO expression system. The thermostable laccase with a molecular weight similar to 30 kDa had a t(1/2) (pH 6.0) of 120 hat 50 degrees C. The homology modelling for laccase structure showed the presence of Cu active centers with His and Cys residues involved in the active site and ligand binding activity of the enzyme, respectively. The K-m, V-max, K-cat and K-car/K-m values of the purified enzyme with ABTS were found to be 0.146 mM, 1.52 U/mg, 1037 s(-1) and 7102.7 s(-1) mM(-1), respectively. The doping of recombinant WSUCFI laccase to commercial enzyme cocktails Accellerase (R) 1500 and Cellic CTec2 improved the hydrolysis of untreated, alkali and acid treated corn stover by 131-2.28 times and bagasse by 132-2.02 times. Further, in-house enzyme cocktails with laccase hydrolyzed untreated, alkali and acid treated bagasse and gave 1.44, 1.1, and 0.92 folds higher sugar, respectively, when compared with Accellerase 1500. The results suggested that thermostable laccase can aid in the improved hydrolysis of lignocellulosic biomass. (C) 2019 Elsevier B.V. All rights reserved.