Physiological aspects involved in production of xylanolytic enzymes by deep-sea hyperthermophilic archaeon Pyrodictium abyssi |
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Authors: | Carvalho Andrade Carolina M M Aguiar Wilson Bucker Antranikian Garo |
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Institution: | (1) Departamento de Engenharia Bioquímica, Universidade Federal do Rio de Janeiro, Escola de Química, 21.949-900 Rio de Janeiro, R.J., Brazil;(2) Institute of Technical Microbiology, Technical University Hamburg-Harburg, Denickestr. 15, D-21071 Hamburg, Germany |
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Abstract: | Xylanases (EC3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could
greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals.
The hyperthermophilic archaeon Pyrodictium abyssi, which was originally isolated from marine hot abyssal sites, grows optimally at 97°C and is a prospective source of highly
thermostable xylanase. Its endoxylanase was shown to be highly thermostable (over 100 m in at 105°C) and active even at 110°C.
The growth of the deep-sea archaeon P. abyssi was investigated using different culture techniques. Among the carbohydrates used, beech wood xylan, birch wood glucuronoxylan
and the arabinoxylan from oats pelt appeared to be good inducers for endoxylanase and β-xylosidase production. The highest
production of arabinofuranosidase, however, was detected in the cell extracts after growth on xylose and pyruvate, indicating
that the intermediate of the tricarboxylic acid cycle acted as a nonrepressing carbon source for the production of thi enzyme.
Electron microscopic studies did not show a significant difference in the cell surface (e.g., xylanosomes) when P. abyssi cells were grown on different carbohydrates. The main kinetic parameters of the organism have been determined. The cell yield
was shown to be very low owing to incomplete substrate utilization, but a very high maximal specific growth rate was determined
(μmax=0.0195) at 90°C and pH 6.0. We also give information on the problems that arise during the fermentation of this hyperthermophilic
archaeon at elevated temperatures. |
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Keywords: | Xylanases Pyrodictium abyssi hyperthermophilic archaea |
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