Thermo-stable xylanases from non conventional yeasts

Abstract

Xylanase is a commercial enzyme that has considerable applications in different types of industries, such as the feed, food, textile and paper industries, amongst others. The main goal of the present work was to select and evaluate the enzyme production from isolated wild yeasts strains obtained from several different Brazilian regions. From a total of 349 strains, two were selected, namely LEB-AAD5 and LEB-AY10, which produced fairly stable enzymes. The characterization studies showed that the strain LEB-AAD5 produced an enzyme with the following optimal range: temperature from 57.5 to 67.5 °C and pH from 4.7 to 5.5, with a half-life of 21.33 hours at 52°C and pH 5.3, Vmax of 1.77 μmol/mL.min and Km of 0.44 g/L. The enzyme from strain LEB-AY10 showed the following optimal range: pH from 4.1 to 4.8 and temperature around 80°C, with a half-life of 11.21 hours at 72°C and pH 5.3, Vmax of 5.47 μmol/mL.min and Km of 1.37 g/L. Xylanase from LEB-AY10 strain is more Thermo-stable than that of LEB-AAD5, both of which belongs to Cryptococcus sp. After optimized using two experimental designs, xylanase production increased by 600%, reaching 11.25 IU/mL under the optimal fermentation conditions (30°C, initial pH of 6.0 and 20 g/L of xylan as substrate). © 2011 Lopes F, et al.