Increased Cellulase Activity of Schizophyllum commune EO22 in Binary Associations with Streptomycetes.

Abstract

A search for new methods for activating and controlling the enzymatic activity of cellulose destructor organisms through joint cultivation is an important problem. Schizophyllum commune is a xylobiont basidiomycete from the group of white rot fungi, is known for its biotechnological versatility, but has still not found efficient application in bioconversion of agricultural wastes and, in particular, cereal straw. The strain Sc. commune EO22 was used to assess the possibility of creating artificial bacterial-fungal associations for the development of an efficient strategy to utilize straw as a by-product of crop production. Streptomyces bacteria possessing cellulolytic activity were co-cultured with S. commune EO22. The dynamics of cellulase activity was determined in Sc. commune EO22 monocultures and binary cultures with Streptomyces griseoaurantiacus Mb4-2, St. thermocarboxydus T1-3, St. hygroscopicus N27-25, and "St. ryensis" H13-3. The cultures were grown in a liquid mineral medium with straw as the only carbon source. Cellulase activity of the Sc. commune EO22 binary cultures with each of the bacterial strains reached its maximum 3-6 days earlier than in the fungal monoculture (a maximum was reached on day 7) under the same conditions. Co-culture with the strain Mb4-2 did not significantly increase the cellulase activity (122 ± 13.1 units/ml) as compared with the fungal monoculture (114.4 ± 37.1 units/ml). Maximum cellulase activities of the binary associations with the strains T1-3, N27-25, and H13-3 exceeded the maximum activity of the Sc. commune EO22 monoculture by factors of 2.3, 1.6, and 1.3, respectively. The degree of straw decomposition was inferred from the weight loss and found to increase by 10.3, 2.3, and 22.4%, respectively, as compared with the fungal monoculture. Decrease in straw weight did not correlate significantly with cellulase activity in the experiment. The results indicate that artificial bacterial-fungal associations provide a promising means for efficient destruction of straw and other cellulose-containing wastes from crop production.