Bioethanol production from raffinate phase of supercritical CO2 extracted Stevia rebaudiana leaves.
The extracts of Stevia rebaudiana are marketed as dietary supplements and utilized as natural sweetening agent in food products. Subsequent to extraction on industrial scale, large quantities of solid wastes are produced. The aim of this study was to investigate the bioconversion efficiency of supercritical CO(2) extracted S. rebaudiana residues. Therefore, leaves were extracted with supercritical CO(2) and ethanol mixture in order to obtain glycosides, then the raffinate phase was hydrolyzed by both dilute acid and various concentrations of cellulase and β-glucosidase cocktail. The maximum yield of reducing sugars reached 25.67 g/L under the optimal conditions of enzyme pretreatment, whereas 32.00 g/L was reached by consecutive enzymatic and acid hydrolyses. Bioethanol yield (20 g/L, 2.0% inoculum, 2 days) based on the sugar consumed was 45.55% corresponding to a productivity of 0.19 kg/m(3)h which demonstrates challenges to be utilized as a potential feedstock for the production of bioethanol.
Department of Bioengineering, Faculty of Engineering, Ege University, 35100 Bornova-Izmir, Turkey.
Isik
I
Coban
Sayit
S
Sargin
Melih Soner
MS
Celiktas
Ozlem
O
Yesil-Celiktas
D056804:Biofuels / Q000032:analysis*; D018533:Biomass; D002245:Carbon Dioxide / Q000737:chemistry*; D000431:Ethanol / Q000138:chemical synthesis*; D005285:Fermentation / Q000187:drug effects; D006868:Hydrolysis / Q000187:drug effects; D010936:Plant Extracts / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry* / Q000187:drug effects; D011887:Raffinose / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism; D036625:Stevia / Q000737:chemistry* / Q000187:drug effects; D013464:Sulfuric Acids / Q000494:pharmacology; D013997:Time Factors; D035501:Uncertainty; D001617:beta-Glucosidase / Q000378:metabolism
D056804:Biofuels; D010936:Plant Extracts; D013464:Sulfuric Acids; D002245:Carbon Dioxide; D000431:Ethanol; C427304:Novozym 188; D001617:beta-Glucosidase; D011887:Raffinose; C033158:sulfuric acid