Characterization of cellobiose fermentations to ethanol by yeasts
Twenty-two different yeasts were screened for their ability to ferment both glucose and cellobiose. The fermentation characteristics of Candida lusitaniae (NRRL Y-5394) and C. wickerhamii (NRRL Y-2563) were selected for further study because their initial rate of ethanol production from cellobiose was faster than the other test cultures. C. lusitaniae produced 44 g/L ethanol from 90 g/L cellobiose after 5-7 days. When higher carbohydrate concentrations were employed, fermentation ceased when the ethanol concentration reached 45-60 g/L. C. lusitaniae exhibited barely detectable levels of BETA-glucosidase, even though the culture actively fermented cellobiose. C. wickerhamii produced ethanol from cellobiose at a rate equivalent to C. lusitaniae; however, once the ethanol concentration reached 20 g/L, fermentation ceased. Using p-nitrophenyl-BETA-D-glucopyranoside (pNPG) as substrate, BETA-glucosidase (3-5 U/mL) was detected when C. wickerhamii was grown anaerobically on glucose or cellobiose. About 35% of the BETA-glucosidase activity was excreted into the medium. The cell-associated activity was highest against pNPG and salicin. Approximately 100-fold less activity was detected with cellobiose as substrate. When employing these organisms in a simultaneous saccharification-fermentation of avicel, using Trichoderma reesei cellulase as the saccharifying agent, 10-30% more ethanol was produced by the two yeasts capable of fermenting cellobiose than by the control, Saccharomyces cerevisiae.
- Research Organization:
- Northern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Peoria, Illinois 61604
- OSTI ID:
- 5567697
- Journal Information:
- Biotechnol. Bioeng.; (United States), Journal Name: Biotechnol. Bioeng.; (United States) Vol. XXV:2; ISSN BIBIA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ALCOHOLS
ALDEHYDES
BIOCONVERSION
CANDIDA
CARBOHYDRATES
CELLOBIOSE
DISACCHARIDES
ENZYME ACTIVITY
ENZYMES
ETHANOL
FERMENTATION
FUNGI
GLUCOSE
GLUCOSIDASE
GLYCOSYL HYDROLASES
HEXOSES
HYDROLASES
HYDROXY COMPOUNDS
MICROORGANISMS
MONOSACCHARIDES
O-GLYCOSYL HYDROLASES
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
PLANTS
PRODUCTION
SACCHARIDES
YEASTS