Location: Renewable Product Technology ResearchTitle: Novel thermostable endo-xylanase cloned and expressed from bacterium Geobacillus sp. WSUCF1) Author
Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2014
Publication Date: 8/1/2014
Citation: Bhalla, A., Bischoff, K.M., Uppugundla, N., Balan, V., Sani, R.K. 2014. Novel thermostable endo-xylanase cloned and expressed from bacterium Geobacillus sp. WSUCF1. Bioresource Technology. 165:314-318. Interpretive Summary: New enzymes that function under harsh industrial conditions of extreme temperature and pH are needed to help overcome some of the technical barriers to using agricultural residues as feedstocks for fuel ethanol production. Thermophilic bacteria are microorganisms that grow at high temperatures and may possess robust enzymes useful to the fermentation industry. In the present study, a gene for an endoxylanase enzyme, which helps break down hemicellulose, was isolated from a thermophilic bacterium, expressed in a laboratory strain of bacteria, and the recombinant enzyme purified. The recombinant enzyme was active over a broad pH range, and was very stable at high temperatures. Results will be valuable to researchers developing new enzymes to serve as biocatalysts in the conversion of agricultural residues to fermentable sugars.
Technical Abstract: A gene encoding a GH10 endo-xylanase from Geobacillus sp. WSUCF1 was cloned and expressed in Escherichia coli. Recombinant endo-xylanase (37 kDa) exhibited high specific activity of 461.0 U/ mg of protein. Endo-xylanase was optimally active on birchwood xylan at 70°C and pH 6.5. Zn2+ and Ca2+ ions increased endo-xylanase activity by 156 and 134%, respectively. The endo-xylanase was found to be highly thermostable at 50°C and 60°C, retaining 82% and 50% of its original activity, respectively, after 60 h. High xylan conversions (92%) were obtained with oat-spelt xylan hydrolysis. Higher glucan and xylan conversions were obtained on AFEX corn stover with an enzyme cocktail containing WSUCF1 endo-xylanase (71% and 47%) as compared to enzyme cocktail containing commercial fungal endo-xylanase (64% and 41%). High specific activity, active at higher pHs, wide substrate specificity, and higher hydrolytic activity on recalcitrant lignocellulosic biomass, make it a suitable candidate for biofuel and bioprocess industries.