Cloning, heterologous expression, and characterization of a metagenome-derived GH10 xylanase with salt and alkali tolerance from Xinjiang saline-alkali soil
摘要
Xylanases are widely used in baking, seafood processing, and paper production, but their performance is often compromised under high-salt, acidic, or alkaline conditions, limiting broader industrial deployment. Identifying robust xylanases from saline-alkali environments is therefore of practical importance. Here, we report a GH10 xylanase gene, XynE102, mined from a saline-alkali soil metagenome from Karamay, Xinjiang. The deduced amino acid sequence shares 69.17% identity with a xylanase from Cellvibrionaceae bacterium (GenBank accession HEY7885703.1). XynE102 was cloned and heterologously expressed in Escherichia coli, and the recombinant enzyme was purified by Ni–NTA affinity chromatography. Using beechwood xylan as substrate, XynE102 exhibited optimal activity at 50 °C and pH 7.0. It retained ≥ 50% relative activity between 30 and 55 °C and pH 5.6–8.6, and ≥ 75% activity in 2.0 M NaCl. Notably, after preincubation at 40 °C for 60 and 120 min, its activity increased to 130% and 165% of the initial value, respectively. Following 24 h preincubation at pH 7–10, residual activity remained ≥ 80%, indicating pronounced alkaline stability. At 1 mM, Mn2+, Co2+, and Fe3+ activated the enzyme, whereas Mg2+, Cu2+, and Cd2+ inhibited it; 1% SDS had no measurable effect. XynE102 primarily hydrolyzed xylan to xylobiose and xylotetraose. It also hydrolyzed alkali-treated corn stalk and hot-water-pretreated wheat bran, yielding reducing sugar concentrations of 5.44 mM and 4.18 mM, respectively, after 24 h. Taken together, these results indicate that XynE102 is a neutral-pH xylanase with notable salt and alkali tolerance, supporting its potential for prebiotic XOS production and food-processing applications under moderate temperature conditions.