Heterologous expression and characterization of a novel halotolerant, thermostable, and alkali-stable GH6 endoglucanase from Thermobifida halotolerans

A novel endoglucanase gene was cloned from Thermobifida halotolerans YIM 90462(T), designated as thcel6A for being a member of glycoside hydrolase family 6. The gene was 1332 bp long and encoded a 443-amino-acid protein with a molecular mass of 45.9 kDa. The purified recombinant endoglucanase had optimal activity at 55 A degrees C and pH 8.5. Thcel6A showed high hydrolytic activities at 25-55 A degrees C and retained 58 % of initial activity after incubation at 90 A degrees C for 1 h. It retained more than 80 % of activity after incubation for 12 h at pH values from 4 to 12. Thcel6A displayed higher hydrolytic activities in 5-15 % NaCl (w/v) than at 0 % NaCl. Activity increased 2.5-fold after incubation with 20 % (w/v) NaCl at 37 A degrees C for 10 min. These properties suggest that this novel endoglucanase has potential for specific industrial application.