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Poster Presentation 6-13
Purification and Characterization of Endoxylanases from Bacillus licheniformis 77-2
Valquiria B. Damiano, Daniela A. Bocchini, Eleni Gomes and Roberto Da-Silva
Laboratory of Process Biochemistry and Applied Microbiology Department of Chemistry UNESP - Universidade Estadual Paulista Rua Cristovao Colombo 2265 Sao Jose do Rio Preto Sao Paulo 15054-000 Brazil
Telephone: (019) 2212354; Fax: (019) 2212356; Email: dasilva@qeg.ibilce.unesp.br
The alkalophilic bacteria Bacillus licheniformis 77-2 produces significant quantities of thermostable, cellulase-free xylanases. In previous work, the crude enzyme was applied in the biobleaching of Kraft pulp, and it was demonstrated that after enzymatic treatment, the same Kappa number was obtained using 33% less ClO2. An improved understanding of the hydrolytic properties of these enzymes is fundamental in the development of industrial application for these xylanases. Therefore, these enzymes were purified by gel filtration and ionic exchange chromatography, which resulted in the isolation of three xylanases. The molecular masses of the three enzymes were estimated to be 17 kDa (X-I) and 40 kDa (X-II and X-III). These xylanases demonstrated good stability up to pH 11 and retained significant hydrolytic activity at alkaline pH. The optimum temperature range for xylanase activities was 70-75oC and the residual activities at 90oC were 50% for the X-I and 90% for the X-II and X-III. The predominant products of xylan hydrolysates indicated that these enzymes were endoxylanases.
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