ASPERGILLUS-SYDOWII MG-49 IS A STRONG PRODUCER OF THERMOSTABLE XYLANOLYTIC ENZYMES

The mycelial fungus Aspergillus sydowii MG49 was found to produce xylanase (EC 3.2.1.8.) and beta-xylosidase (EC 3.2.1.37) in high specific activity (72.8 and 9.8 U mg-1 protein, respectively) in a short incubation period of 72 h when grown on xylan as the sole carbon source. Xylose, the breakdown product of xylan, could also induce the production of both the xylanolytic enzymes efficiently. A. sydowii was capable of growth on several underutilized agricultural residues, which also, led to the production of these enzymes in high specific activity. Xylanase enzyme produced was secreted extracellularly, but beta-xylosidase was found to have intramycelial localization, unlike the reports of extracellular production of this enzyme by many of the other organisms. The optimum production pH for both the enzymes was 4.0, while the production temperature was 30-degrees-C. However, both these enzymes exhibited thermostable characteristics, having maximum in vitro enzyme activity at 60-degrees-C. Production of xylanase was found to be strongly influenced by the addition of certain amino acids in the enzyme fermentation medium, while the pretreatment of crude xylanolytic enzymes with additives such as metal ions and surfactants also affected the specific activity of the enzymes. This fungus did not produce any cellulolytic enzymes.