Characterization of the xylanolytic enzyme system of the extreme thermophilic anaerobic bacteria Thermotoga maritima, T. neapolitana, and T. thermarum

The extreme thermophilic anaerobic bacteria Thermotoga maritima, T. neapolitana, and T. thermarum when grown on xylan produce extremely thermoactive xylanases, β-xylosidases and α-arabinofuranosidases. Most of these enzymes are active over a broad temperature and pH range, namely between 40 and 110°C and pH 4 to 9. The xylanases are active towards soluble, as well as insoluble xylan. Unlike the enzyme system of T. maritima and T. thermarum, the xylanase activity of T. neapolitana is activated (up to 211%) in the presence of Ca²⁺, Mg²⁺, Co²⁺, and Mn²⁺. The xylanolytic enzyme system of T. thermarum is inactive towards cellulose. Xylan hydrolysis experiments indicate the presence of endoxylanases in the enzyme preparation of all strains investigated, with the main products being xylobiose, xylotriose, and larger xylooligosaccharides.