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Thermomonospora fusca BD25 produces relatively high levels of activity of endoxylanases. Only oat spelt xylan, RBB-xylan and birchwood xylan reacted with endoxylanases with the maximum specific activity of 47.65 U mg-1 protein on birchwood xylan | Turk J Biol 24 (2000) 737–752 © TÜBİTAK Characterization of Endoxylanase Activity From Thermomonospora Fusca BD25 Münir TUNCER Mersin University, Faculty of Arts and Science, Department of Biology, Çiftlikköy, 33342 Mersin-TURKEY Received: 04.08.1999 Abstract: Thermomonospora fusca BD25 produces relatively high levels of activity of endoxylanases. Only oat spelt xylan, RBB-xylan and birchwood xylan reacted with endoxylanases with the maximum specific activity of 47.65 U mg-1 protein on birchwood xylan. The endoxylanase remained stable up to 70 °C. At 60 °C endoxylanase activity showed stability (92 %) for 16 h, however it showed a half-life of 8 h at 70 °C and 30 min at 80 °C in the absence of substrate at pH 8.0. The relative endoxylanase activity in the pH ranges of 6.5 to 9.5 remained between 68 % and 72 % of the activity at pH 8.0. The apparent Km value for the crude endoxylanase was 6.66 mg of oat spelt xylan ml-1, while the Vmax value was 2.5 µmol reducing sugar min-1 ml-1. Endoxylanase activity was affected by the addition of xylobiose (1 mM) to the reaction mixture of endoxylanase preparation and resulted in approximately 25 % reduction in activity. Also, the addition of supernatant fluids from cultures grown on xylan (reducing sugar concentration of 1 mg ml-1 xylose equivalent) to the reaction mixture resulted in approximately 30 % reduction in activity. Key Words: Endo-1,4-β-xylanase, lignocellulose degradation, Thermomonospora fusca, xylan, actinomycete. Thermomonospora fusca BD25’ten Elde Edilen Endoksilanaz Enziminin Karakterizasyonu Özet: Termofilik bir aktinomiset olan Thermomonospora fusca BD25, diğer organizmalara oranla daha yüksek seviyede endoksilanaz enzimleri üretmektedir. Endoksilanaz enzimlerinin spesifik aktivitelerini belirlemek amacı ile yapılan çalışmalarda, kullanılan substratlardan sadece yulaf ksileni, huş ağacı ksileni ve RBB-ksilenin reaksiyon verdiği belirlenmiş olup en yüksek spesifik aktivitenin (47,65 U mg-1 protein) huş .
