Analysis of enzymes of the hemicellulose complex from Geobacillus stearothermophilus 22 VKPM B-11678 isolated from Garga hot spring, Russia

• Enzymes of hemicellulase complex G. stearothermophilus 22 VKPM B-11678 were expressed in E. coli.
• We determined enzymes activity on synthetic substrates at different pH and temperature ranges.
• We determined enzymes activity in the presence of IL at different concentrations.
• We determined enzymes activity on the natural substrate.

Hemicellulase complex enzymes are important in lignocellulose processing. The aim of this work was to study the hemicellulose complex proteins of Geobacillus stearothermophilus 22 VKPM B-11678, isolated from sediment from Garga Hot Spring, Barguzin River Valley, Baikal, Russia, for plant biomass hydrolysis, and examine their activity under highly ionic conditions. Genes encoding several thermophilic xylanases were cloned, including α-glucuronidase, endo-1,4-β-xylanase, xylan-1,4-β-xylosidase, and α-l-arabinofuranosidase. The enzymatic activities of the proteins were studied under a wide range of pH (4–8) and temperature (45–70 °C) conditions. Optimal pH and temperature values were determined as follows: α-glucuronidase, 50 °C and pH 7.5; endo-1,4-β-xylanase, 55 °C and pH 5.7; xylan-1,4-β-xylosidase, 65 °C and pH 5.0. Under optimal conditions, the enzymes showed the following activities: α-glucuronidase, 23.26 μmol min−1 mg−1; endo-1,4-β-xylanase, 2.9 μmol min−1 mg−1; and xylan-1,4-β-xylosidase, 58.03 μmol min−1 mg−1, demonstrating that some of the enzymes are active in ionic liquid (IL). This characteristic is important because the use of ILs is a promising method for pretreatment of lignocellulosic biomass.