Background: In recent years the need for a low-cost ethanol production has stimulated the research on the one-step microbial conversion of agronomic wastes in biofuel. Yeast strain possessing the combination of polysaccharides utilisation and ethanol production properties could be very promising. Objectives: 1. Investigation of the extracellular enzymatic activity (EEA) profile of yeast strains previously selected for their optimal fermentative performance. 2. Selection of strains with the most interesting enzymatic profile to be used for further studies on bioethanol production from biomass. Methods: 220 Saccharomyces cerevisiae strains and 180 non-Saccharomyces strains were isolated from grape marcs on the basis of their fermentative vigour. Strains were screened for their activity on cellulose, hemicellulose, starch, pectin and protein. Results: Few strains showed activity on cellulose, pectin, starch and protein, while no xylanolytic strains were observed.Thirteen strains of S. cerevisiae, potentially able to use starch as the sole carbon source, were selected. Their weak growth on starch minimal agar plates was unexpected and suggests an extensive biochemical, physiological and genetic study on their amylolytic enzyme(s).Two non-Saccharomyces strains were selected for the production of cellulase and starchdegrading enzymes. Their enzymatic activity was monitored in liquid assays. Conclusions: The preliminary results encourages further studies on the EEA screening of oenological yeasts. Few strains, selected for their optimal fermentative ability, showed an improvable hydrolytic activity on complex polysaccharides (cellulose, starch, pectin), main components of low-cost agricultural residues. This approach represents a first step towards an interesting ethanol-production strategy through the development of a wild-type yeast, or a good starting base for the construction of recombinant strains, for the microbial conversion of biomass in biofuel.
Extracellular enzymes profiling in oenological yeast strain for future biofuel applications.
FAVARO, LORENZO;BASAGLIA, MARINA;CASELLA, SERGIO
2009
Abstract
Background: In recent years the need for a low-cost ethanol production has stimulated the research on the one-step microbial conversion of agronomic wastes in biofuel. Yeast strain possessing the combination of polysaccharides utilisation and ethanol production properties could be very promising. Objectives: 1. Investigation of the extracellular enzymatic activity (EEA) profile of yeast strains previously selected for their optimal fermentative performance. 2. Selection of strains with the most interesting enzymatic profile to be used for further studies on bioethanol production from biomass. Methods: 220 Saccharomyces cerevisiae strains and 180 non-Saccharomyces strains were isolated from grape marcs on the basis of their fermentative vigour. Strains were screened for their activity on cellulose, hemicellulose, starch, pectin and protein. Results: Few strains showed activity on cellulose, pectin, starch and protein, while no xylanolytic strains were observed.Thirteen strains of S. cerevisiae, potentially able to use starch as the sole carbon source, were selected. Their weak growth on starch minimal agar plates was unexpected and suggests an extensive biochemical, physiological and genetic study on their amylolytic enzyme(s).Two non-Saccharomyces strains were selected for the production of cellulase and starchdegrading enzymes. Their enzymatic activity was monitored in liquid assays. Conclusions: The preliminary results encourages further studies on the EEA screening of oenological yeasts. Few strains, selected for their optimal fermentative ability, showed an improvable hydrolytic activity on complex polysaccharides (cellulose, starch, pectin), main components of low-cost agricultural residues. This approach represents a first step towards an interesting ethanol-production strategy through the development of a wild-type yeast, or a good starting base for the construction of recombinant strains, for the microbial conversion of biomass in biofuel.
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