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United States Department of Agriculture

Agricultural Research Service

Research Project: GENOMICS AND ENGINEERING OF STRESS TOLERANT MICROBES FOR LOWER COST PRODUCTION OF ETHANOL FROM LIGNOCELLULOSE

Location: Bioenergy Research

Title: High solid loading hydrolyzate-tolerant strains of Scheffersomyces (Pichia) stipitis exhibiting reduced diauxic lag and higher ethanol productivity)

Author
item Slininger, Patricia - Pat
item Balan, Venkatesh
item Sousa, Leonardo
item Dale, Bruce
item Cotta, Michael

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/21/2011
Publication Date: N/A
Citation:

Interpretive Summary:

Technical Abstract: During the fermentation of lignocellulosic hydrolyzates to ethanol by native pentose-fermenting yeasts such as Scheffersomyces (Pichia) stipitis NRRL Y-7124, the switch from glucose to xylose uptake results in a diauxic lag unless process strategies to prevent this are applied. Further investigation showed that ethanol concentrations around 50 g/L fully repressed enzyme induction although xylose transport into the cells was observed to be occurring. Increasing degrees of repression were documented between 15 and 45 g/L ethanol. Repitched cell populations grown on xylose resulted in faster fermentation rates, particularly on xylose but also on glucose, and eliminated diauxic lag and stalling during mixed sugar conversion, despite ethanol accumulations in the 60-70 g/L range. The process strategy of priming cells on xylose was key to the successful utilization of high mixed sugar concentrations because specific enzymes for xylose utilization could be induced before ethanol concentration accumulated to an inhibitory level. S. stipitis strains now adapted to perform in high solid loading (18%) AFEX-pretreated corn stover hydrolyzates show enhanced fermentation rates and ethanol yields, improved ethanol tolerance and enzyme inductions, and reduced diauxic lag.

Last Modified: 8/24/2016
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