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Prefermentation improves xylose utilization in simultaneous saccharification and co-fermentation of pretreated spruce.

Wiman, Magnus LU ; Olofsson, Kim LU and Lidén, Gunnar LU (2009) In Biotechnology for Biofuels 2(1).
Abstract
ABSTRACT: BACKGROUND: Simultaneous saccharification and fermentation (SSF) is a promising process option for ethanol production from lignocellulosic materials. However, both the overall ethanol yield and the final ethanol concentration in the fermentation broth must be high. Hence, almost complete conversion of both hexoses and pentoses must be achieved in SSF at a high solid content. A principal difficulty is to obtain an efficient pentose uptake in the presence of high glucose and inhibitor concentrations. Initial glucose present in pretreated spruce decreases the xylose utilization by yeast, due to competitive inhibition of sugar transport. In the current work, prefermentation was studied as a possible means to overcome the problem of... (More)
ABSTRACT: BACKGROUND: Simultaneous saccharification and fermentation (SSF) is a promising process option for ethanol production from lignocellulosic materials. However, both the overall ethanol yield and the final ethanol concentration in the fermentation broth must be high. Hence, almost complete conversion of both hexoses and pentoses must be achieved in SSF at a high solid content. A principal difficulty is to obtain an efficient pentose uptake in the presence of high glucose and inhibitor concentrations. Initial glucose present in pretreated spruce decreases the xylose utilization by yeast, due to competitive inhibition of sugar transport. In the current work, prefermentation was studied as a possible means to overcome the problem of competitive inhibition. The free hexoses, initially present in the slurry, were in these experiments fermented before adding the enzymes, thereby lowering the glucose concentration. RESULTS: This work shows that a high degree of xylose conversion and high ethanol yields can be achieved in SSF of pretreated spruce with a xylose fermenting strain of Saccharomyces cerevisiae (TMB3400) at 7% and 10% water insoluble solids (WIS). Prefermentation and fed-batch operation, both separately and in combination, improved xylose utilization. Up to 77% xylose utilization and 85% of theoretical ethanol yield (based on total sugars), giving a final ethanol concentration of 45 g L-1, were obtained in fed-batch SSF at 10% WIS when prefermentation was applied. CONCLUSION: Clearly, the mode of fermentation has a high impact on the xylose conversion by yeast in SSF. Prefermentation enhances xylose uptake most likely because of the reduced transport inhibition, in both batch and fed-batch operation. The process significance of this will be even greater for xylose-rich feedstocks. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biotechnology for Biofuels
volume
2
issue
1
publisher
BioMed Central
external identifiers
  • wos:000272007400001
  • pmid:19356227
ISSN
1754-6834
DOI
10.1186/1754-6834-2-8
language
English
LU publication?
yes
id
3edb5e2c-caaf-4646-9ecb-432a6bbf667b (old id 1392269)
date added to LUP
2009-05-06 13:28:11
date last changed
2016-09-20 04:23:46
@article{3edb5e2c-caaf-4646-9ecb-432a6bbf667b,
  abstract     = {ABSTRACT: BACKGROUND: Simultaneous saccharification and fermentation (SSF) is a promising process option for ethanol production from lignocellulosic materials. However, both the overall ethanol yield and the final ethanol concentration in the fermentation broth must be high. Hence, almost complete conversion of both hexoses and pentoses must be achieved in SSF at a high solid content. A principal difficulty is to obtain an efficient pentose uptake in the presence of high glucose and inhibitor concentrations. Initial glucose present in pretreated spruce decreases the xylose utilization by yeast, due to competitive inhibition of sugar transport. In the current work, prefermentation was studied as a possible means to overcome the problem of competitive inhibition. The free hexoses, initially present in the slurry, were in these experiments fermented before adding the enzymes, thereby lowering the glucose concentration. RESULTS: This work shows that a high degree of xylose conversion and high ethanol yields can be achieved in SSF of pretreated spruce with a xylose fermenting strain of Saccharomyces cerevisiae (TMB3400) at 7% and 10% water insoluble solids (WIS). Prefermentation and fed-batch operation, both separately and in combination, improved xylose utilization. Up to 77% xylose utilization and 85% of theoretical ethanol yield (based on total sugars), giving a final ethanol concentration of 45 g L-1, were obtained in fed-batch SSF at 10% WIS when prefermentation was applied. CONCLUSION: Clearly, the mode of fermentation has a high impact on the xylose conversion by yeast in SSF. Prefermentation enhances xylose uptake most likely because of the reduced transport inhibition, in both batch and fed-batch operation. The process significance of this will be even greater for xylose-rich feedstocks.},
  articleno    = {8},
  author       = {Wiman, Magnus and Olofsson, Kim and Lidén, Gunnar},
  issn         = {1754-6834},
  language     = {eng},
  number       = {1},
  publisher    = {BioMed Central},
  series       = {Biotechnology for Biofuels},
  title        = {Prefermentation improves xylose utilization in simultaneous saccharification and co-fermentation of pretreated spruce.},
  url          = {http://dx.doi.org/10.1186/1754-6834-2-8},
  volume       = {2},
  year         = {2009},
}