Isolation and characterization of xylan-degrading alkali-tolerant thermophiles

Two alkali-tolerant thermophilic bacterial strains with xylanolytic activity were isolated by continuous cultivation from samples collected near Bulgarian hot springs. Xylanases produced by the two strains were similar with respect to temperature and pH optimum (70–75°C and pH 6.5–7.0) as well as their thermostability. The xylanases were thermostable at 70°C for 30 min. Xylanolytic activity was resistant to pH 5.5–8.0 (strain SP) and 6.0–7.5 (strain BC). Zymogram analysis of the culture supernatant ultrafiltrate showed two xylanase active bands corresponding to a protein band of 92 kDa.