Isolation of xylanase preparations for biotechnological applications from Aspergillus niger A(3)

The cude xylanase preparation (P-1) for biotechnological applications was obtained from the culture supernatant of Aspergillus niger A(3) by precipitation with ethanol. The pH optimum (5.0) and temperature optimum (40 degrees 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 degrees 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 degrees C - temperature of hydrolysis, pH 5.0 and 72 h time of hydrolysis) the xylans of two substrates (xylan ex larch sawdust and pretreated corn 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-l. 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 degrees C for P-2 and 40 degrees C for P-3) were estimated.