Studies on the extracellular cellulolytic enzyme complex produced by clostridium thermocellum

Crude cellulolytic activity produced extracellularly by Clostridium thermocellum ATCC 27405 attacked crystalline cellulose (Avicel), a soluble cellulose derivative (carbosymethylcellulose), and a chromogenic derivative of the latter (trinitrophenylcarboxymethylcellulose). The crude enzyme complex had an apparent K/sub m/ of 3.6 mg/ml for carboxymethylcellulose and 3.3 mg/ml for its dyed derivative. The unique lack of inhibition of exo-..beta..-glucanase (measured on Avicel) and endo-..beta..-glucanase activity (measured on carboxymethylcellulose and its trinitrophenylcarboxymethyl derivative) by glucose or cellobiose is of considerable interest. Growth of C. thermocellum took place only on cellulose and cellobiose of some 50 carbon sources tested. Addition of glucose to cellobiose cultures did not affect growth or enzyme production. A mutant (AS-39) which produced twice as much exo- and endo-..beta..-glucanase as did ATCC 27405 was isolated.