Studies of the Enzymatic Degradation of Cellulose.

1. The enzyme preparations tested for cellulolytic activity were from pure cultures of Streptomyces sp. QM B 814 and of four different Hymenomycetes, viz. Polyporus annosus Fr. and three strains of Collybia velutipes (Curt. ex Fr.) Quéll, i.e. two monocaryotic wildtypes L 1 and L 11, as well as the dicaryotic combination (F 29/157 X F 28/42) between two arginineless mutants. 2. The enzyme activity against cellulose sol has been measured turbidimetrically, the method being referred to as the photometric method in earlier papers. (Norkrans 1950 a, b). The activity has also been expressed in terms of reducing substances, glucose formed, and changes in average degree of polymerization (DP). Furthermore the enzyme attack has been studied by electron microscopy of the cellulose sol. 3. In all tests the preparation of Collybia velutipes (F 29/157 X F 28/42) showed the greatest total activity as well as the highest reaction rate. 4. According to the turbidimetrical readings, as to the DP_n-determinations, the enzyme preparations had a great influence on the cellulose sol during the first hours of incubation. The Z-values increased rapidly, after the first twenty hours representing 60 to 90 per cent of the end-Z-values. The initial DP_n-value of 338 decreased to 50-60 in four (or six) hours. 5. The paper chromatogram indicates the presence of cellobiose as well as another, slower-moving substance, presumably cellotriose, as breakdown products besides glucose. 6. A comparison between the DP_n-values and the corresponding glucose values lend support to the theory of a random-splitting of the cellulose chain. 7. Expressed in terms of reducing substances, the breakdown did not in any case proceed to more than about 65 per cent of the total initial amount of cellulose. The polymerization seemed to proceed until a DP_n of about 50. These limits seem to be related rather to the morphological structure of the cellulose sol particles than to the enzyme inactivation. Electron micrographs of such cellulose residues lend support to this conclusion, since they revealed a mass of distinct and fairly homogeneous particles about 300 Å long and about half as wide. These stood in clear contrast to those of the untreated cellulose sots, containing larger aggregates of longer disordered fibers forming an irregular network or unresolved lumps. [ABSTRACT FROM AUTHOR]