Isolation of Xylanase Preparations for Biotechnological Applications from Aspergillus Niger A₃

ABSTRACT

The crude xylanase preparation (P-1) for biotechnological applications was obtained from the culture supernatant of Aspergillus niger A₃ by precipitation with ethanol. The pH optimum (5.0) and temperature optimum (40 °C) were estimated. This crude xylanase preparation was stable at pH 5.0 (80 % retained initial activity for 24 h) and temperature between 20 - 45 °C (75 % retained initial activity for over 24 h). At the optimal experimental conditions for enzyme hydrolysis (2.5 % substrate concentration, 0.1 % concentration of the crude xylanase preparation, 50 °C—temperature of hydrolysis, pH 5.0 and 72 h time of hydrolysis) the xylans of two substrates (xylan ex larch sawdust and pretreated com stalks with 1 % NaOH) were hydrolyzed to 55 and 65%, respectively. Six forms of xylanases were detected by molecular-sieve column chromatography of the P-1. The maximal active xylanase peaks (Fr-II and Fr-IV) were purified further by anion-exchange column chromatography. The two xylanase preparations P-2 (Fr-II-III) and P-3 (Fr-IV-II) were obtained. The pH optimums (4.0 for P-2 and 4.5 for P-3) and temperature optimums (60°C for P-2 and 40° C for P-3) were estimated.