An investigation of bacterial and fungal xylanolytic systems

Yaşınok, Ayşegül Ersayın
Endo-b-1,4 xylanases (EC. are typically produced as a mixture of different hydrolytic enzymes such as b-1,4-xylosidase (EC. , a-Larabinofuranosidases (EC., and feruloyl esterase (EC that hydrolyze xylan molecule, which constitutes 20-30% of the weight of wood and agricultural wastes. Thus, xylan, a renewable biomass, can be utilized as a substrate for the preparation of many products such as fuels, solvents and pharmaceuticals. Besides, xylanolytic enzymes themselves are also used in food,feed, textile industries and pre-bleaching of kraft. In the first part of the study, xylanolytic systems of a soil isolate Bacillus pumilus SB-M13 and a thermophilic fungus Scytalidium thermophilum were investigated. Production rate and type of xylanolytic changed depending on the carbon source and the microorganism. However, xylanolytic enzyme production was found to be sequential, in synergy and under the control of carbon catabolite repression for both microorganisms. In the second part, B. pumilus SB-M13 b-1,4 xylanase was purified and biochemically characterized. The enzyme was stable at alkaline pHs and highest activity was observed at 60°C and pH 7.5. Enzyme Km and kcat values were determined as 1.87 mg/ml and 43,000 U/mg, respectively. B. pumilus SB-M13 and S .thermophilum a-L-arabinofuranosidases were also purified and biochemically characterized. Although produced from a mesophilic microorganism, B. pumilus SB-M13 arabinofuranosidase was quite thermostable. Moreover, unlike other fungi, S. thermophilum produced alkaline stable arabinofuranosidases. Both enzymes were multimeric, alkaline stable and most active at 70°C and pH 7.0. However, when compared to S. thermophilum, catalytic power of B. pumilus SB-M13 arabinofuranosidase was higher.


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Citation Formats
A. E. Yaşınok, “An investigation of bacterial and fungal xylanolytic systems,” Ph.D. - Doctoral Program, Middle East Technical University, 2006.