Rapid ethanol production by Saccharomyces cerevisiae in a membrane bioreactor

Conference poster, 2013

Robust polysiloxane-ACA capsules for prolonged ethanol production from wood hydrolyzate by Saccharomyces cerevisiae Päivi Ylitervo,a,b Carl Johan Franzén b and Mohammad J. Taherzadeh a a University of Borås, School of Engineering, Sweden b Chalmers University of Technology, Industrial Biotechnology, Sweden The recalcitrance of lignocellulose makes it difficult to hydrolyze and toxic inhibitors are formed during its decomposition. The formed inhibitors can severely affect the fermentability of the hydrolyzate. Encapsulating the fermenting yeast can be a potential option to make the cells more inhibitor and stress tolerant when compared with suspended yeast. In the encapsulation process the yeast is enclosed in a thin semi-permeable membrane surrounding the cells in the liquid core. To apply encapsulation for industrial applications the capsules need to be mechanically stable for long periods. Therefore, a new encapsulation method was developed were alginate-chitosan-alginate (ACA) capsules were treated with hydrolyzed 3-aminopropyltrietoxysilane (hAPTES) to reinforce capsules with polysiloxane (PS). PS-ACA-capsules treated with 1.5% and 3.0% hAPTES were very robust and only 0-1% capsules broke during the mechanical shear test performed after five batch cultivations. Of the untreated capsules, 25% burst within 6 h. The yeast in 3.0% hAPTES treated PS-ACA-capsules did not produce any ethanol during cultivations. However, capsules treated with 1.5% hAPTES were significantly stronger and showed similar ethanol production profile to untreated ACA-capsules cultivated in hydrolyzate. The produced PS-ACA-capsules were easily prepared and demonstrated high stability, reusability, and good ethanol production which are crucial features to make capsules the applicable at large scale for ethanol production.