Thermal stability of β-xylanases produced by different Thermomyces lanuginosus strains

The thermostability of β-xylanases produced by nine thermophilic Thermomyces lanuginosus strains in a coarse corn cob medium was assessed. The xylanase produced by T. lanuginosus strain SSBP retained 100% of its activity after 6 h at temperatures up to 65°C. In comparison seven ATCC strains and the DSM 5826 strain of T. lanuginosus only retained 100% xylanase activity at temperatures up to 60°C. Culture filtrates of T. lanuginosus strain SSBP grown on coarse corn cobs, oatspelts xylan, birchwood xylan, wheatbran, locust beangum, and sugar cane bagasse, retained 100% xylanase activity at temperatures up to 60°C. The xylanase produced on corn cobs was the most thermostable and showed an increase of approximately 6% from 70°C to 80°C. The T1/2 of all strains at 70°C at pH 6.5 varied greatly from 63 min for strain ATCC 28083 to 340 min for strain SSBP. The xylanase of strain SSBP was much less thermostable at pH 5.0 and pH 12.0 with T1/2 values of 11.5 min and 15 min, respectively at 70°C. At 50°C, the enzyme of T. lanuginosus strain SSBP produced on coarse corn cobs was stable within the pH range of 5.5–10.0. Furthermore, the enzyme retained total activity at 60°C for over 14 days and at 65°C for over 48 h. The xylanase of T. lanuginosus strain SSBP possesses thermo- and pH stability properties that may be attractive to industrial application.