微生物与生化技术杂志

抽象的

Thermo-Stable Xylanases from Non Conventional Yeasts

Lopes F, Motta F, Andrade C C P, Rodrigues M I and Maugeri-Filho F

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-AAD 5 and LEB-AY 10 , which produced fairly stable enzymes. The characterization studies showed that the strain LEB-AAD 5 produced an enzyme with the following optimal range: temperature from 57.5 to 67.5 ºC and pH from 4.7 to 5.5, with a half-life of 21.33 hours at 52ºC and pH 5.3, Vmax of 1.77 μmol/mL.min and Km of 0.44 g/L. The enzyme from strain LEB-AY 10 showed the following optimal range: pH from 4.1 to 4.8 and temperature around 80ºC, with a half-life of 11.21 hours at 72ºC and pH 5.3, Vmax of 5.47 μmol/mL.min and Km of 1.37 g/L. Xylanase from LEB-AY 10 strain is more Thermo-stable than that of LEB-AAD 5 , 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).