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Prefermentation improves ethanol yield in separate hydrolysis and cofermentation of steam-pretreated wheat straw

Nielsen, Fredrik LU ; Zacchi, Guido LU ; Galbe, Mats LU and Wallberg, Ola LU (2016) In Sustainable Chemical Processes 4(10).
Abstract
Agricultural residues, such as wheat straw, are feasible substrates for ethanol fermentation provided that pentoses and hexoses can be converted efficiently. Separate hydrolysis and cofermentation (SHCF) constitute a framework for improvement of conversion efficiency, because it permits independent optimization of the enzymatic hydrolysis and cofermentation steps. A drawback is that the high glucose concentrations present in SHCF repress xylose utilization and constrain ethanol yields. To improve xylose utilization the xylose-rich hydrolyzate liquor was separated from glucose-rich solids and the phases were cofermented sequentially. Prefermentation of the xylose-rich hydrolyzate liquor followed by fed-batch cofermentation of glucose-rich... (More)
Agricultural residues, such as wheat straw, are feasible substrates for ethanol fermentation provided that pentoses and hexoses can be converted efficiently. Separate hydrolysis and cofermentation (SHCF) constitute a framework for improvement of conversion efficiency, because it permits independent optimization of the enzymatic hydrolysis and cofermentation steps. A drawback is that the high glucose concentrations present in SHCF repress xylose utilization and constrain ethanol yields. To improve xylose utilization the xylose-rich hydrolyzate liquor was separated from glucose-rich solids and the phases were cofermented sequentially. Prefermentation of the xylose-rich hydrolyzate liquor followed by fed-batch cofermentation of glucose-rich prehydrolyzed solids enabled sequential targeting of xylose and glucose conversion. The aim was to improve the xylose conversion by lowering the glucose repression of the xylose uptake. Various prefermentation configurations and feed patterns for prehydrolyzed solids were examined. Prefermentation increased ethanol yields overall, and fed-batch prefermentation reduced xylitol production. The best results were obtained by balancing promotion of efficient xylose conversion with maintained yeast viability. Fed-batch prefermentation and a single addition of prehydrolyzed solids, elicited an ethanol yield of 0.423 g·g−1 and a xylitol yield of 0.036 g·g−1. (Less)
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publication status
published
subject
in
Sustainable Chemical Processes
volume
4
issue
10
publisher
Springer Open
ISSN
2043-7129
DOI
10.1186/s40508-016-0054-9
language
English
LU publication?
yes
id
e55f1434-d584-4d75-8201-6338999ab41a
alternative location
http://sustainablechemicalprocesses.springeropen.com/articles/10.1186/s40508-016-0054-9
date added to LUP
2016-08-03 16:19:59
date last changed
2016-08-19 11:56:10
@article{e55f1434-d584-4d75-8201-6338999ab41a,
  abstract     = {Agricultural residues, such as wheat straw, are feasible substrates for ethanol fermentation provided that pentoses and hexoses can be converted efficiently. Separate hydrolysis and cofermentation (SHCF) constitute a framework for improvement of conversion efficiency, because it permits independent optimization of the enzymatic hydrolysis and cofermentation steps. A drawback is that the high glucose concentrations present in SHCF repress xylose utilization and constrain ethanol yields. To improve xylose utilization the xylose-rich hydrolyzate liquor was separated from glucose-rich solids and the phases were cofermented sequentially. Prefermentation of the xylose-rich hydrolyzate liquor followed by fed-batch cofermentation of glucose-rich prehydrolyzed solids enabled sequential targeting of xylose and glucose conversion. The aim was to improve the xylose conversion by lowering the glucose repression of the xylose uptake. Various prefermentation configurations and feed patterns for prehydrolyzed solids were examined. Prefermentation increased ethanol yields overall, and fed-batch prefermentation reduced xylitol production. The best results were obtained by balancing promotion of efficient xylose conversion with maintained yeast viability. Fed-batch prefermentation and a single addition of prehydrolyzed solids, elicited an ethanol yield of 0.423 g·g−1 and a xylitol yield of 0.036 g·g−1.},
  author       = {Nielsen, Fredrik and Zacchi, Guido and Galbe, Mats and Wallberg, Ola},
  issn         = {2043-7129},
  language     = {eng},
  month        = {07},
  number       = {10},
  publisher    = {Springer Open},
  series       = {Sustainable Chemical Processes},
  title        = {Prefermentation improves ethanol yield in separate hydrolysis and cofermentation of steam-pretreated wheat straw},
  url          = {http://dx.doi.org/10.1186/s40508-016-0054-9},
  volume       = {4},
  year         = {2016},
}