OPTIMIZATION OF XYLANASE PRODUCTION BY A HYPERXYLANOLYTIC MUTANT STRAIN OF FUSARIUM-OXYSPORUM

Cultural conditions for xylanase production by a hyperxylanolytic muta nt strain (NTG-19) of Fusarium oxysporum were optimized in shake flask cultures. The mutant secretes high levels of xylanase on birchwood xy lan as well as on agricultural residues. Among different agricultural residues and inorganic/organic nitrogen sources tested, wheat bran and peptone produced the highest titres of xylanase. The optimum concentr ation of wheat bran (4%, w/v) produced a titre of 46.2 IU/ml in 96 h. Optimum pH and temperature for xylanase production by F. oxysporum NTG -19 were pH 3.0-3.5 and 30 degrees C, respectively. Addition of Tween- 80 and olive oil to the medium significantly improved the enzyme yield s. When the mutant was grown in a controlled fermenter, the xylanase y ield was enhanced by about 50%. (65 IU/ml). Optimum pH and temperature for xylanase activity was 6.0 and 55 degrees C. The enzyme was most s table up to 50 degrees C, stability decreased above 55 degrees C, but 40% activity was retained at 80 degrees C for 2 h. (C) 1998 Elsevier S cience Ltd. All rights reserved.