New fungal enzymes for total hydrolysis of biomass: Diplomityö

Enzymatic hydrolysis of lignocellulosic biomass is one of the bottlenecks in feasible production of lignocellulosic ethanol. The aim of this thesis was to discover novel lignocellulose-degrading enzymes that could enhance the hydrolysis performance of existing enzyme mixtures in the total hydrolysis of biomass. The objective was to screen novel fungal strains secreting enzymes which improve the hydrolytic efficiency of known enzyme mixtures.
First, the strains (numbered from 1 to 31) were screened on the basis of their secreted cellulolytic and hemicellulolytic enzyme activities and their performance in the hydrolysis of microcrystalline cellulose and hydrothermally pre-treated wheat straw. Second, synergistic effects were studied between the most interesting fungal culture supernatants and two known enzyme mixtures (a commercial enzyme product Celluclast produced by the fungus Trichoderma reesei and a thermostable enzyme mixture developed in the HYPE-project) in standardised hydrolysis of cellulose and pre-treated wheat straw.
Detailed enzyme activity profiles were determined in the most interesting culture supernatants selected on the basis of the synergy study.

Several fungal culture supernatants enhanced the hydrolytic performance of the known enzyme mixtures. Clearest synergistic effects with T. reesei Celluclast and the thermo enzyme mixture were observed with the culture supernatants of strains 2, 6, 19, 22 and 27. The cultures of strains 22 and 27 showed the best overall synergy with both enzyme mixtures in the hydrolysis of both substrates.
The cultures of strains 6 and 19 showed remarkable synergy with Celluclast in the hydrolysis of wheat straw, whereas the culture of strain 2 acted synergistically with the thermo enzyme mixture, especially in the hydrolysis of wheat straw. High xylanase activity was detected in the cultures of strains 2, 22 and 27, which could at least partly explain their good synergistic effects in the hydrolysis of wheat straw. The culture of strain 27 showed a versatile enzyme profile including high xylanase, endoglucanase and β-xylosidase activities.
Altogether, high xylanase activity appeared to be at least partly responsible for the high level of synergy between the novel fungal broths and the known enzyme mixtures. Several interesting strains secreting enzymes having clear synergistic effects with existing enzyme preparations were discovered in this work.