Résumé
Alkaline xylanases produced by four different strains of "Bacillus pumilus" were characterized. The optimal pH and temperature were pH 9.0 and 60ºC for strain 13(a), and pH 8.0 and 55ºC for strains 5(2), 5(14), and 4(a). Under these conditions the following activities were found after 10 min in the presence of 1(per cent) xylan (birchwood): 328 U.ml(-1), 131 U.ml(-1), 90 U.ml(-1), and 167 U.ml(-1), respectively, for the four strains. The enzymes were stable at 40ºC, with 40(per cent) of the xylanase activity remaining after 2 hours for the enzymes of strain 5(2) and 60(per cent) for the other three strains. Stability at 50ºC was improved by addition of glycerol. Taking into account the conditions under which kraft pulps are bleached during the manufacture of paper xylanases from "B. pumilus" exhibit favorable potential for application to bleaching in the paper making process.