Purificação parcial e caracterização da enzima xilanase produzida pelo fungo amazônico Pycnoporus sanguineus l. F. (murr)

Abstract

Pycnoporus sanguineus are excellent decomposers of organic matter, presenting important role in its habitat. In this study, a strain of Pycnoporus sanguineus isolated from soil of rural area of Parintins, Amazonas, Brazil, was grown on solid medium of malt, 35 0C for 8 days to obtain a pure culture and malt liquid medium plus 2% glucose and 120 rpm for a period of 10 days to produce the enzyme xylanase, β-xylosidases, β-glucosidase, CMCase, and laccase avicelase. Among these enzymes, the production of xylanase was evaluated and the enzyme was partially purified and characterized. Optimum yield was obtained at pH 6.5 at 35 °C, 120 rpm and 196h of cultivation. The culture filtrate (200 mL), obtained under the conditions optimized in the previous steps, was precipitated at 70% ammonium sulfate and centrifuged for 60 min at 4 0C and rotation of 4000 rpm. One mL of the fraction precipitated in which xylanolytic activity was detected, was filtered using a filter Millex GV 0.22 micrometre (Durapore Membrane PYDF) and subsequently injected into a chromatograph type AKTA Purifier UPC 900, 5:11 UNICORN system, using an anion exchange column HiTrap SP XL 1 mL capacity, equilibrated in 50 mM Tris-HCl pH 7.4. The degree of purity, the fractions that showed xylanase activity, as well as their protein profiles were analyzed by electrophoresis on SDS-PAGE (12% polyacrylamide), where the molar mass of 39.44 kDa was determined. The optimal conditions for enzyme activity were 75 °C and pH 8.0. The thermal stability of the xylanase enzyme from P. sanguineus was partially purified high 65 to 85 ºC, being more stable 75 0C. The stability at different pHs was high between 4.5 and 8.8. With birchwood xylan (2.0 to 50 mg / mL), the Km value of the enzyme was 0.32786 mg / ml, and the Vmax value was 12.70648 mol min-1 mL-1 when the reaction was performed at 75 °C and pH 8.0. These results indicate the possible use of this enzyme complex industrial processes that require the use of xylanases at alkaline pH and high stability in different pHs and high temperatures.