Two thermostable xylanases with different acid-alkalinity coexistence in one bacterium screened using lignocellulosic biomass and its applications.

Aims: This study aimed to isolate and characterize thermostable xylanases from the thermophilic bacterium Geobacillus stearothermophilus CFH 71344, screened from Yunnan hot springs, for their potential in lignocellulosic biomass conversion and xylooligosaccharide (XOS) production.

Methods and results: Two xylanases, Xyn2415 and Xyn2429, were heterologously expressed and biochemically characterized. Biochemical characterization revealed that enzyme Xyn2415 exhibited optimal activity at pH 9.0 and 70°C, while enzyme Xyn2429 showed optimal activity at pH 6.0 and 80°C. Both enzymes demonstrated significant thermostability, retaining considerable activity even after prolonged exposure to high temperatures. The kinetic parameters indicated that Xyn2429 had higher catalytic efficiency than Xyn2415. The enzymes also exhibited distinct substrate preferences and metal ion sensitivities. When applied to beechwood xylan hydrolysis, Xyn2415 and Xyn2429 produced different XOS profiles, with Xyn2415 preferentially generating short-chain XOS and Xyn2429 producing longer-chain XOS.

Conclusions: The coexistence of these enzymes in one bacterium highlights their adaptability to varying environmental conditions, offering potential for cost-effective and efficient industrial applications in lignocellulosic biorefining and prebiotic production.