Expression and Characterization of a Thermostable α-Glucuronidase from Geobacillus kaustophilus

Abstract

Fossil fuels are a crucial resource for the global economy, but they also contribute to greenhouse gas emissions and environmental pollution. Lignocellulosic biomass, which includes cellulose, hemicellulose, and lignin obtained from plants, is a promising alternative to fossil fuels. It can help address these problems while reducing environmental impact. Enzymatic pre-treatment is used to degrade lignocellulosic biomass into subunits. The degradation of the hemicellulose structure involves accessory enzymes of industrial importance, such as α-glucuronidase. α-glucuronidases (EC 3.2.1.139) catalyze the hydrolysis of the α-1,2-glycosidic bond between α-D-glucuronic acid (GlcA) or its 4-o-methyl ether form (MeGlcA) and d-xylose units in the structure of xylooligosaccharides. The aim of this study was cloning, heterologous expression and biochemical characterization of the α-glucuronidase enzyme from the thermophilic bacterium Geobacillus kaustophilus. With this aim, the codon optimized α-glucuronidase gene was cloned into pQE-30 vector, overexpressed in E. coli BL21 (DE3), and purified with nickel affinity chromatography. The biochemical characterization of the purified α-glucuronidase revealed that the enzyme has activity at elevated temperatures between 65-90 °C. Additionally, Geobacillus kaustophilus α-glucuronidase enzyme showed higher activity at acidic pH values from pH 4.0 to 6.5. This is the first study to report the gene cloning, recombinant expression and biochemical characterization of α-glucuronidase which could be used as accessory enzyme from a thermophilic bacterium Geobacillus kaustophilus.