Thermal stabilization by polyols of β‐xylanase from Bacillus amyloliquefaciens

Purified endo-β-1,4-xylanase of Bacillus amyloliquefaciens MIR 32 retained 100% of its activity after 4 days of incubation at 50°C. Sorbitol (400 mg cm -3 ) produced a 63-fold increase in the half-life of the enzyme at 65°C, which was only 29 min at this temperature in the absence of the polyol. This thermal stabilizing activity increased exponentially in respect to sorbitol concentration in the range 250-400 mg cm -3 and was dependent on the pH, showing a maximum at pH values between 5.25 and 8.0. The circular dichroism (CD) thermal scanning profile (50°C h -1 ) at 224 nm showed that changes in the secondary structure of xylanase started at 65°C, while in the presence of sorbitol (400 mg cm -3 ) these modifications started at 80°C. This study indicated that sorbitol might be a valuable stabilizer for the use of β-xylanase from B. amyloliquefaciens at high temperatures.