GROWTH AND PRODUCTION OF XYLANOLYTIC ENZYMES BY THE EXTREME THERMOPHILIC ANAEROBIC BACTERIUM THERMOTOGA-THERMARUM

Cultivation of the extreme thermophilic anaerobic bacterium Thermotoga thermarum at 77 degrees C on xylan was accompanied by the formation o f heat-stable endoxylanase (136 U/l), beta-xylosidase (44 U/l) and alp ha-arabinofuranosidase (10 U/l). These enzymes were mainly associated with the cells and could not be released by detergent treatment (0.1-1 .0 mM lamidopropyl)-dimethylammonio]-1-propanesulphonate (CHAPS)}. End oxylanases with a molecular weight of 40, 83 and 100 kDa were induced when xylan or xylose were used as substrates for growth. In the presen ce of other sugars like glucose, maltose, arabinose or starch, low con centrations of the low-molecular-weight endoxylanase (40 kDa) was dete cted. Xylose was found to be the best substrate for the induction of b eta-xylosidase and alpha-arabinofuranosidase but not for growth. Culti vation of T. thermarum in a dialysis batch fermenter resulted in a sig nificant increase in cell concentration and enzyme level. A total cell count of 1.3 x 10(9) cells/ml and 202 U/l of endoxylanase were measur ed when partially soluble birchwood xylan was used as the carbon sourc e. The use of insoluble beechwood xylan as the substrate caused the el evation of the maximal cell concentration and enzyme level up to 2.0 x 10(9) cells/ml and 540 U/l, respectively.