LAUSR

Abstract Eucalyptus leaves were investigated as a source for the isolation of xylanase producing microorganisms. A total of 37 isolates were obtained after a series of enrichment steps. Seven of the isolates were xylanase positive in an agar screening experiment and were further analyzed in liquid media with beechwood xylan as carbon source. A yeast identified as Pseudozyma sp. showed the highest xylanase activity in tested conditions. Afterwards, different lignocellulosic residues were studied as substrates for xylanase production by this strain and the best results were obtained with corncob. Yeast's xylanase with a molecular weight of 19.9 kDa showed the maximum activity at pH 4.8 and 50 °C. Thermostability was observed at 30 °C with a 60% activity retention after 10 days. By the hydrolytic activity of the enzyme was characterized as an endoxylanase, similar as the ones found in family GH 10, from the products obtained by beechwood xylan hydrolysis.