Physiological Aspects Involved in Production of Xylanolytic Enzymes by Deep-Sea Hyperthermophilic Archaeon Pyrodictium abyssi

Abstract

Xylanases (EC 3.2.1.8) 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 degrees C and is a prospective source of highly thermostable xylanase. Its endoxylanase was shown to be highly thermostable (over 100 min at 105 degrees C) and active even at 110 degrees 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 beta-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 this 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 (micromax = 0.0195) at 90 degrees C and pH 6.0. We also give information on the problems that arise during the fermentation of this hyperthermophilic archaeon at elevated temperatures.

Biotechnological applications of archaeal enzymes from extreme environments

“…They cleave β-1,4-xylosidic linkages in xylans [ 85 ]. These enzymes have been reported in the halophilic archaeon Halorhabdus utahensis [ 110 ] and in the hyperthermophilic archaeon Pyrodictium abyssi [ 111 ] (see Table 7 ). On the other hand, β-1,4-Xylosidases (EC 3.2.1.37) hydrolyze β-1,4-xylans and disaccharides, such as xylobiose, generating D-xylose [ 37 ].…”

Hyperthermostable Thermotoga maritima xylanase XYN10B shows high activity at high temperatures in the presence of biomass-dissolving hydrophilic ionic liquids

“…With regard to hyperthermostable xylanases, those found in natural microbes still have the highest level of thermostability. The temperature optimum of Thermotoga maritima GH10 xylanase was 105 °C in a 5-min assay (Winterhalter and Liebl 1995 ; Reeves et al 2000 ; Ihsanawati et al 2005 ) and that of Pyrodictium abyssi GH10 xylanase was 110 °C (Andrade et al 2001 ).…”

Extremophilic Prokaryotic Endoxylanases: Diversity, Applicability, and Molecular Insights

“…On characterization, both of these enzymes showed their temperature optima in the hyperthermophilic range, i.e., above 60 • C. Besides, both shared halophilic properties by having activity up to 30% NaCl (w/v) concentration. Similarly, a hyperthermophilic archaeon Pyrodictium abyssi produced an extremely thermostable xylanase that showed its activity at 105 • C-110 • C. It is one of the most thermophilic xylanases reported so far from any archaeal sources (Andrade et al, 2001). Several polysaccharides have been used as an inducer for the production of xylanase as well as β-xylosidases.…”