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Purification and characterization of thermostable xylanase and beta-xylosidase by the thermophilic bacterium Bacillus thermantarcticus (Articolo in rivista)

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Purification and characterization of thermostable xylanase and beta-xylosidase by the thermophilic bacterium Bacillus thermantarcticus (Articolo in rivista) (literal)

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Lama, L., Calandrelli, V., Gambacorta, A., Nicolaus, B. (2004)
Purification and characterization of thermostable xylanase and beta-xylosidase by the thermophilic bacterium Bacillus thermantarcticus
in Research in microbiology (Paris)
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There are numerous reports of promising xylanase producing bacteria including Bacillus. Only a few of them have both xylanase and beta-xylosidase activities. Xylanase from Bacillus thermantarcticus had high thermophilia and thermostability. Xylanase and beta-xylosidase from B. thermanatarcticus show interesting properties for biotechnological applications, such as optimal pH and temperature activity, thermostability, the absence of cellulolytic activities and high portions of low-member xylooligomers. The latter are preferred in industrial applications and medicine. Moreover, both enzymes were induced by xylan, an inexpensive waste substrate useful on a commercial scale. The cost of the enzyme production is an important factor in the evaluation of its suitability for industrial application. B. thermanatarcticus growing on xylan as sole carbon source, has a characteristic xylan digestion system in two steps that is advantageous for recovery of hydrolysis products by modulating growth conditions and physico-chemical parameters. (literal)

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Bacillus thermantarcticus, a thermophilic bacterium isolated from Antarctic geothermal soil near the crater of Mount Melbourne, produced extracellular xylanase and beta-xylosidase. Each extracellular enzyme was separated by gel filtration with Sephacryl S-200 and further purified to homogeneity. The optimum temperatures were 80°C for xylanase at pH 5.6 and 70°C for beta-xylosidae at pH 6.0. the isoelectric points and moleculas masses were 4.8 and 45Kda for xylanase and 4.2 and 150Kda for beta-xylosidase, respectively. Xylanase was stable at 60°C for 24h, whereas it showed a half life at 70°C of 24 h and at 80°C for 50 min. Beta-xylosidase activity did not decrease after 1 h at 60°C. Km of xylanase for xylan was 1.6mg/ml, Km of beta-xylosidase for p-nitrophenyl-beta-d-xylopyranoside was 0.5 mM and for o- nitrophenyl-beta-d-xylopyranoside was 1.28 mM. The action of two enzymes on xylan gave only xylose. (literal)

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