THE CELLULASE ACTIVITY OF AN EXTREME THERMOPHILE

The carboxymethylcellulase activity concentrated from the extremely thermophilic anaerobe H173 was found to have a pH optimum of 6.5-7.0. The enzyme activity was stabilised by the addition of dithiothreitol and CaCl2.2H2O and was very stable at 80-degrees-C, retaining 77% of the initial activity after 120 min incubtation. At 90-degrees-C however, 50% activity remained after 9 min and after 120 min only 3% of the initial activity remained. With the enzyme dissolved in buffer, glucose and cellobiose were formed from the hydrolysis of Avicel. In culture medium the Avicel-solubilising activity was insensitive to the presence of up to 50 mM glucose and showed linear glucose accumulation over a period of days at 70-degrees-C. HPLC analysis established that glucose was the major end-product of hydrolysis in the culture broths.