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Title: Evolved strains of Scheffersomyces stipitis achieving high ethanol productivity on acid- and base-pretreated biomass hydrolyzate at high solids loading

Lignocellulosic biomass is an abundant, renewable feedstock useful for the production of fuel-grade ethanol via the processing steps of pretreatment, enzyme hydrolysis, and microbial fermentation. Traditional industrial yeasts do not ferment xylose and are not able to grow, survive, or ferment in concentrated hydrolyzates that contain enough sugar to support economical ethanol recovery since they are laden with toxic byproducts generated during pretreatment. Repetitive culturing in two types of concentrated hydrolyzates was applied along with ethanol challenged xylose-fed continuous culture to force targeted evolution of the native pentose fermenting yeast Scheffersomyces (Pichia) stipitis strain NRRL Y-7124 maintained in the ARS Culture Collection, Peoria, IL. Isolates collected from various enriched populations were screened and ranked based on relative xylose uptake rate and ethanol yield. Ranking on hydrolyzates with and without nutritional supplementation was used to identify those isolates with best performance across diverse conditions. Robust S. stipitis strains adapted to perform very well in enzyme hydrolyzates of high solids loading ammonia fiber expansion-pretreated corn stover (18% weight per volume solids) and dilute sulfuric acid-pretreated switchgrass (20% w/v solids) were obtained. Improved features include reduced initial lag phase preceding growth, significantly enhanced fermentation rates, improved ethanol tolerance and yield, reduced diauxic lagmore » during glucose-xylose transition, and ability to accumulate >40 g/L ethanol in <167 h when fermenting hydrolyzate at low initial cell density of 0.5 absorbance units and pH 5 to 6.« less
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [3] ;  [1]
  1. USDA National Center for Agricultural Utilization Research, Peoria, IL (United States). Bioenergy Research Unit.
  2. USDA National Center for Agricultural Utilization Research, Peoria, IL (United States). Bacterial Foodborne Pathogens and Mycology Research.
  3. Michigan State Univ., East Lansing, MI (United States). Great Lakes Bioenergy Research Center (GLBRC).
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 1754-6834
BioMed Central
Research Org:
Great Lakes Bioenergy Research Center (GLBRC), Michigan State Univ., East Lansing, MI (United States)
Sponsoring Org:
Country of Publication:
United States
09 BIOMASS FUELS lignocellulose; biofuel; adaptation; yeast; Pichia stipitis; fermentation