ARS | Publication request: Inhibition of the switch from glucose to xylose by ethanol concentration: the advantage of cell recycle

Submitted to: American Institute of Chemical Engineers Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 6, 2009
Publication Date: October 15, 2009
Citation: Slininger, P.J. 2009. Inhibition of the switch from glucose to xylose by ethanol concentration: the advantage of cell recycle [abstract]. American Institute of Chemical Engineers. p. 36.

Technical Abstract: To expand the biomass-to-fuel ethanol industry, process strategies are needed to breakdown lignocellulose to fermentable sugars and to foster the production of microorganisms which can survive and ferment the resulting hexose and pentose sugars while exposed to inhibitors such as ethanol. In hydrolyzates, the switch from glucose to xylose uptake can result in diauxic lag unless steps are taken to prevent this. The use of recycled cells can eliminate diauxy if cells are appropriately conditioned. When cells were primed on glucose, the length of this lag was a function of the glucose concentration consumed (and the ethanol concentration accumulated) prior to the switch from glucose to xylose fermentation. The impact of ethanol on enzyme induction and the length of diauxy was explored. Priming recycled cells with a high xylose concentration was observed to induce faster fermentation rates and to eliminate diauxic lag during mixed sugar conversion by Pichia stipitis NRRL Y-7124 despite ethanol accumulations exceeding 60 g/L. Process strategies to lower the cost of ethanol from biomass are suggested by the results of this work.