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Process development for combined pentose and hexose fermentation

Nielsen, Fredrik LU (2016)
Abstract
Second-generation ethanol from lignocellulose is a sustainable alternative that can partially replace fossil fuels. To be competitive with first generation ethanol from sugar and starch crops and fossil fuels, the conversion efficiency and ethanol yields of second-generation ethanol conversion processes must be improved. Improving the performance of the fermenting microorganism and efficiently convert both glucose and xylose in lignocellulosic biomass is imperative to achieve these targets. This thesis addresses means to improve the performance of the biochemical steps of the lignocellulose-to-ethanol process. The main focus has been on enhancing the xylose utilization of xylose-fermenting Saccharomyces cerevisiae by adapting the... (More)
Second-generation ethanol from lignocellulose is a sustainable alternative that can partially replace fossil fuels. To be competitive with first generation ethanol from sugar and starch crops and fossil fuels, the conversion efficiency and ethanol yields of second-generation ethanol conversion processes must be improved. Improving the performance of the fermenting microorganism and efficiently convert both glucose and xylose in lignocellulosic biomass is imperative to achieve these targets. This thesis addresses means to improve the performance of the biochemical steps of the lignocellulose-to-ethanol process. The main focus has been on enhancing the xylose utilization of xylose-fermenting Saccharomyces cerevisiae by adapting the yeast to lignocellulosic hydrolysates during propagation and developing novel co-fermentation strategies that promote xylose utilization. Co-fermentation strategies based on separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) were investigated.

Furthermore, scale-up of co-fermentation strategies and the use of multiple and blended feedstocks in the conversion process were investigated. The findings show that adaptation of the yeast to the conditions in fermentation during propagation provides a broad adaptive response that improves fermentation performance of xylose-fermenting S. cerevisiae. Co-fermentation designs that take the xylose consumption patterns of xylose-fermenting S. cerevisiae into consideration can further enhance the xylose utilization and ethanol yields. Furthermore, feedstocks with similar attributes and blends thereof could be concurrently pretreated and co-fermented, eliciting comparable ethanol yields of the whole range of feedstocks and feedstock blends. This suggests that feedstocks with similar attributes can be used interchangeably to improve supply efficiency and hedge economic and technologic risks. Scale-up experiments show that the advanced co-fermentation strategies can be scaled-up from lab scale to process development and demonstration scale and maintain comparable ethanol yields, thus bringing the lab-scale process improvements closer to implementation at commercial scale. (Less)
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author
supervisor
opponent
  • Professor Svein Jarle Horn, Norwegian University of Life Sciences, Ă…s, Norway
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Bioethanol, Lignocellulose, Xylose fermentation, Co-fermentation, Process design, Agricultural residues, Saccharomyces cerevisiae
pages
196 pages
publisher
Department of Chemical Engineering, Lund University
defense location
lecture hall K:C, Center for Chemistry and Chemical Engineering, Naturvetarvägen 12, Lund
defense date
2016-09-08 13:15
ISBN
978-91-7422-454-2
language
English
LU publication?
yes
id
6da7de5a-5c64-4486-ac7a-54c5147fbe3b
date added to LUP
2016-08-03 17:08:16
date last changed
2016-09-19 08:45:20
@misc{6da7de5a-5c64-4486-ac7a-54c5147fbe3b,
  abstract     = {Second-generation ethanol from lignocellulose is a sustainable alternative that can partially replace fossil fuels. To be competitive with first generation ethanol from sugar and starch crops and fossil fuels, the conversion efficiency and ethanol yields of second-generation ethanol conversion processes must be improved. Improving the performance of the fermenting microorganism and efficiently convert both glucose and xylose in lignocellulosic biomass is imperative to achieve these targets. This thesis addresses means to improve the performance of the biochemical steps of the lignocellulose-to-ethanol process. The main focus has been on enhancing the xylose utilization of xylose-fermenting <i>Saccharomyces cerevisiae</i> by adapting the yeast to lignocellulosic hydrolysates during propagation and developing novel co-fermentation strategies that promote xylose utilization. Co-fermentation strategies based on separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) were investigated.<br/><br/>Furthermore, scale-up of co-fermentation strategies and the use of multiple and blended feedstocks in the conversion process were investigated. The findings show that adaptation of the yeast to the conditions in fermentation during propagation provides a broad adaptive response that improves fermentation performance of xylose-fermenting <i>S. cerevisiae</i>. Co-fermentation designs that take the xylose consumption patterns of xylose-fermenting <i>S. cerevisiae</i> into consideration can further enhance the xylose utilization and ethanol yields. Furthermore, feedstocks with similar attributes and blends thereof could be concurrently pretreated and co-fermented, eliciting comparable ethanol yields of the whole range of feedstocks and feedstock blends. This suggests that feedstocks with similar attributes can be used interchangeably to improve supply efficiency and hedge economic and technologic risks. Scale-up experiments show that the advanced co-fermentation strategies can be scaled-up from lab scale to process development and demonstration scale and maintain comparable ethanol yields, thus bringing the lab-scale process improvements closer to implementation at commercial scale.},
  author       = {Nielsen, Fredrik},
  isbn         = {978-91-7422-454-2},
  keyword      = {Bioethanol,Lignocellulose,Xylose fermentation,Co-fermentation,Process design,Agricultural residues,Saccharomyces cerevisiae},
  language     = {eng},
  month        = {08},
  pages        = {196},
  publisher    = {ARRAY(0x7a5a5e8)},
  title        = {Process development for combined pentose and hexose fermentation},
  year         = {2016},
}