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Fermentation and Cultivation Technology for Improved Ethanol Production from Lignocellulose

Rudolf, Andreas LU (2007)
Abstract (Swedish)
Popular Abstract in Swedish

Arbetet i denna avhandling syftar till att förbättra etanolproduktionen från lignocellulosa. Etanol framställd från förnyelsebara råvaror har fått förnyad uppmärksamhet på grund av den växande medvetenheten om den globala uppvärmningen och farhågor för en trytande tillgång på olja. Lignocellulosa utgör en potentiell råmaterialkälla för framtida storskalig etanolproduktion. För att kunna erhålla etanol från lignocellulosa måste dess beståndsdelar i form av cellulosa, hemicellulosa och lignin brytas ner så att de jäsbara sockerarterna frigörs. Denna hydrolys kan antingen katalyseras av olika syror eller av enzymer. Lignocellulosahydrolysat innehåller ofta ämnen som inhiberar mikroorganismer och... (More)
Popular Abstract in Swedish

Arbetet i denna avhandling syftar till att förbättra etanolproduktionen från lignocellulosa. Etanol framställd från förnyelsebara råvaror har fått förnyad uppmärksamhet på grund av den växande medvetenheten om den globala uppvärmningen och farhågor för en trytande tillgång på olja. Lignocellulosa utgör en potentiell råmaterialkälla för framtida storskalig etanolproduktion. För att kunna erhålla etanol från lignocellulosa måste dess beståndsdelar i form av cellulosa, hemicellulosa och lignin brytas ner så att de jäsbara sockerarterna frigörs. Denna hydrolys kan antingen katalyseras av olika syror eller av enzymer. Lignocellulosahydrolysat innehåller ofta ämnen som inhiberar mikroorganismer och därmed orsakar en försämrad etanolproduktion. Eftersom etanol är har ett lågt försäljningspris är det viktigt att processen är robust, enkel och effektiv.



Det övergripande målet med det aktuella projektet var att ytterligare förbättra jäsningen av lignocellulosahydrolysat genom att modifiera existerande och utveckla nya metoder för cellodling och jäsning. Råmaterialet som utvärderades var gran och sockerrörsbagasse. Gran är en billig och lättillgänglig svensk råvara medan sockerrörsbagasse är en biprodukt får lantbruket som finns tillgänglig i stora kvantiteter i tropiska och subtropiska länder.



Resultaten från det experimentella arbetet visade att förbättring av existerande odlings och jäsningsstrategier avsevärt förbättrade jäsning av lignocellulosahydrolysat under industriella betingelser. En existerande metod för semikontinuerlig jäsning av svagsyra-hydrolysat modifierares vilket möjliggjorde uppskalning till PDU-skala. Det visade sig att uppodling av jäst på hydrolysat förbättrade dess inhibitortålighet avsevärt. Detta gjorde det möjligt att öka torrhalten i samtidig hydrolys och jäsning (SSF) samtidigt som jästtillsatsen kunde minskas. Mer effektivt utnyttjande av de olika sockerarterna i hydrolysaten kunde uppnås genom att använda xylosjäsande jäststammar. Både rekombinant Saccharomyces cerevisiae och en naturligt xylosjäsande jäst utvärderades. Även om båda jästarna kunde jäsa en stor del av xylosen så rådde inget tvivel om att S. cerevisiae var överlägset mest robust under industriella förhållanden (Less)
Abstract
The work presented in this thesis has been aiming at improving ethanol production from lignocellulose. Ethanol from renewable resources is receiving renewed attention due to apprehensions of global warming and dwindling oil reserves. Lignocellulose constitutes a potential raw material source for large scale ethanol production. To produce ethanol from lignocellulose, the hemicellulose and cellulose components have to be hydrolyzed to saccharides by acid or enzymatic hydrolysis. Lignocellulose hydrolysates often contain inhibitors that affect the fermentation negatively and cause a decrease in ethanol productivity. Since ethanol is a low-value product it is crucial that the production process is relatively simple, robust and... (More)
The work presented in this thesis has been aiming at improving ethanol production from lignocellulose. Ethanol from renewable resources is receiving renewed attention due to apprehensions of global warming and dwindling oil reserves. Lignocellulose constitutes a potential raw material source for large scale ethanol production. To produce ethanol from lignocellulose, the hemicellulose and cellulose components have to be hydrolyzed to saccharides by acid or enzymatic hydrolysis. Lignocellulose hydrolysates often contain inhibitors that affect the fermentation negatively and cause a decrease in ethanol productivity. Since ethanol is a low-value product it is crucial that the production process is relatively simple, robust and efficient.



The overall aim of the current work was to further improve fermentation of lignocellulose hydrolysates by modifying existing and developing new fermentation and cultivation methods. The lignocellulosic materials evaluated in the current work were spruce and sugar cane bagasse. Spruce is an abundant feedstock in Sweden, whereas sugar-cane bagasse is an abundant agricultural residue, available in large quantities in the tropical and subtropical zone.



It was shown that by improving fermentation techniques and developing methods for on-site yeast production, significantly improved fermentation of lignocellulose hydrolysates at industrially applicable conditions could be achieved.



An existing fed-batch method for controlled fermentation of toxic hydrolysates was further developed to allow for scale-up. It was demonstrated that fast and efficient fermentation of an inhibitory dilute-acid hydrolysate from spruce in 20 L-scale could be obtained by applying a feed-rate control that used the total gas flow from the reactor as input-signal.



It was shown that precultivation of yeast on hemicellulose hydrolysate significantly improved its inhibitor tolerance and made it possible to significantly increase the content of water insoluble solids in SSF. Ethanol concentrations above 5 % (v/v) were attained in simultaneous saccharification and fermentation of steam-pretreated spruce by using yeast adapted to the hydrolysate.



More efficient utilization of the different saccharides in simultaneous saccharification and fermentation of sugar cane bagasse could be obtained by using xylose-fermenting yeasts. Both recombinant Saccharomyces cerevisiae and naturally xylose-fermenting yeast were evaluated. Even though high xylose conversion was obtained with both yeasts, S. cerevisiae proved much more suitable for fermentation at industrial conditions. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor du Preez, James, Dept. of Microbial, Biochemical and Food Biotechnology, University of the Free State, South Africa
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Kemiteknik och kemisk teknologi, Chemical technology and engineering, Fermentation, Lignocellulose, Hydrolysis, Bioethanol
pages
162 pages
publisher
Department of Chemical Engineering, Lund University
defense location
Kemicentrum, Lunds Tekniska Högskola Sal K:B Getingevägen 60, Lund
defense date
2007-03-23 13:15
ISBN
978-91-628-7067-6
language
English
LU publication?
yes
id
2b0791df-9811-460a-afb4-6cbff435fda0 (old id 548196)
date added to LUP
2007-10-09 15:37:31
date last changed
2016-09-19 08:45:11
@phdthesis{2b0791df-9811-460a-afb4-6cbff435fda0,
  abstract     = {The work presented in this thesis has been aiming at improving ethanol production from lignocellulose. Ethanol from renewable resources is receiving renewed attention due to apprehensions of global warming and dwindling oil reserves. Lignocellulose constitutes a potential raw material source for large scale ethanol production. To produce ethanol from lignocellulose, the hemicellulose and cellulose components have to be hydrolyzed to saccharides by acid or enzymatic hydrolysis. Lignocellulose hydrolysates often contain inhibitors that affect the fermentation negatively and cause a decrease in ethanol productivity. Since ethanol is a low-value product it is crucial that the production process is relatively simple, robust and efficient.<br/><br>
<br/><br>
The overall aim of the current work was to further improve fermentation of lignocellulose hydrolysates by modifying existing and developing new fermentation and cultivation methods. The lignocellulosic materials evaluated in the current work were spruce and sugar cane bagasse. Spruce is an abundant feedstock in Sweden, whereas sugar-cane bagasse is an abundant agricultural residue, available in large quantities in the tropical and subtropical zone.<br/><br>
<br/><br>
It was shown that by improving fermentation techniques and developing methods for on-site yeast production, significantly improved fermentation of lignocellulose hydrolysates at industrially applicable conditions could be achieved.<br/><br>
<br/><br>
An existing fed-batch method for controlled fermentation of toxic hydrolysates was further developed to allow for scale-up. It was demonstrated that fast and efficient fermentation of an inhibitory dilute-acid hydrolysate from spruce in 20 L-scale could be obtained by applying a feed-rate control that used the total gas flow from the reactor as input-signal.<br/><br>
<br/><br>
It was shown that precultivation of yeast on hemicellulose hydrolysate significantly improved its inhibitor tolerance and made it possible to significantly increase the content of water insoluble solids in SSF. Ethanol concentrations above 5 % (v/v) were attained in simultaneous saccharification and fermentation of steam-pretreated spruce by using yeast adapted to the hydrolysate.<br/><br>
<br/><br>
More efficient utilization of the different saccharides in simultaneous saccharification and fermentation of sugar cane bagasse could be obtained by using xylose-fermenting yeasts. Both recombinant Saccharomyces cerevisiae and naturally xylose-fermenting yeast were evaluated. Even though high xylose conversion was obtained with both yeasts, S. cerevisiae proved much more suitable for fermentation at industrial conditions.},
  author       = {Rudolf, Andreas},
  isbn         = {978-91-628-7067-6},
  keyword      = {Kemiteknik och kemisk teknologi,Chemical technology and engineering,Fermentation,Lignocellulose,Hydrolysis,Bioethanol},
  language     = {eng},
  pages        = {162},
  publisher    = {Department of Chemical Engineering, Lund University},
  school       = {Lund University},
  title        = {Fermentation and Cultivation Technology for Improved Ethanol Production from Lignocellulose},
  year         = {2007},
}