Immobilized fungal biocatalysts for the production of cellulase complex hydrolyzing renewable plant feedstock

We discuss characteristics of the directional formation of samples of heterogeneous biocatalysts based on immobilized cells of different microscopic fungi that are characterized by high productivity of cellulases with different substrate specificities (endoglucanases, exoglucanases, and beta-glucosidases). Samples of immobilized cells characterized by maximum productivity of the enzymes of cellulase complex are selected based on our study of the catalytic and operating characteristics of the designed biocatalysts. It is found that a biocatalyst based on Aspergillus terreus spores immobilized in polyvinyl alcohol cryogel is the best of the ones available. It is shown for the first time that the developed biocatalyst retains a high level of productivity for the full complex of cellulases when using various substrate inducers of enzyme biosynthesis, such as birch and oak sawdust, and rice and wheat straw. We demonstrate the possibility of efficiently using cellulase complexes obtained as a result of the functioning of immobilized cells in the saccharification of various cellulose-containing agricultural wastes and the conversion of the obtained sugars to organic solvents (ethanol, butanol) considered to be promising alternative fuels. The concentrations of organic solvents in media with immobilized cells are considerably higher than those found for free cells of the same microorganisms.