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Use of a newly isolated extreme thermophile for the production of 2nd generation bioethanol
Tomás, Ana Faria ; De Francisci, Davide; Karakashev, Dimitar Borisov; Angelidaki, Irini
Publication date:
2012
Document Version
Final published version
Link to publication
Citation (APA):
Tomás, A. F., De Francisci, D., Karakashev, D. B., & Angelidaki, I. (2012). Use of a newly isolated extreme
thermophile for the production of 2nd generation bio-ethanol. Poster session presented at 14th International
Symposium on Microbial Ecology, Copenhagen, Denmark.
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Use of a newly isolated extreme thermophile
nd
for the production of 2 generation bio-ethanol
Ana Faria Tomás*, Davide De Francisci, Dimitar Karakashev and Irini Angelidaki
*Corresponding author: [email protected]; DTU Environment, Miljøvej 113, DK-2800 Kgs. Lyngby
Background and aim
Questions
Bio-ethanol produced by microbial fermentation is currently recognized
as one of the most promising candidates for replacing fossil fuels. The
use of residual biomass as the substrate is recommended, in order to
minimize the impact in land use and greenhouse gas emissions.
However, lignocellulose can be composed of up to 25 % of pentose
sugars, which are typically not degraded by the currently used industrial
ethanologenic strains. The goal of this work is to isolate an extreme
thermophilic microorganism capable of stoichiometric conversion of
pentoses to ethanol, and use it for 2nd generation bio-ethanol
production.
•Can all the fractions of a pre-treated lignocellulosic
substrate be used in the process?
•Is the new isolate tolerant to typical inhibitors
derived from pre-treatment of lignocellulose?
• Can the process be improved if combined with
fermentation by Saccharomyces cerevisae?
Characteristics of the new isolate
4
3
2
1
Pre-treatment
+
Enzymatic
hydrolysis
Fermentation
with S. cerevisae
Rapeseed
straw
Fermentation with
Thermoanaerobacter
DTU01
0.3
0.5
1.2
2.4
3.4
Initial furfural concentration (g l-1)
4
Concentration (g l-1)
• Batch tests using basic anaerobic medium
8
S. cerevisae
Xylose
Ethanol
Thermoanaerobacter DTU01
6
4
2
0
0
Methods overview
Glucose
0
0.0
• Isolation using Hungate roll tubes
Lactate
Residual xylose
Concentration (g l-1)
0.43 g/gconsumed xylose
Ethanol yield
Other products Acetate, lactate, hydrogen
Acetate
Ethanol
Residual Furfural/HMF
Concentration (g l-1)
Thermophilic UASB reactor for
Isolation source hydrogen production from household
waste
Thermoanaerobacter
Genus
0.5-2 µm rods, spore-forming
Morphology
Opt. growth
70°C, pH 7
conditions
Glucose, xylose, arabinose, sucrose,
Substrates
cellobiose, inulin, starch, xylan, pectin
utilized
2-step fermentation
Inhibitor tests
3
2
1
50
100
Fermentation time (h)
Fig. 2. Glucose, xylose and ethanol profiles during a
two-step fermentation process with S. cerevisae and
Thermoanaerobacter DTU01, using pre-treated
rapeseed straw (5 % solid loading, as well as the liquid
fractions of the pre-treatment) as substrate. The
dashed lines refer to a control batch where only strain
DTU01 was used (only one fermentation step).
Strains used
0
0.0
0.5
1.2
2.8
3.4
Initial HMF concentration (g l-1)
Fig. 1. End product and residual xylose and inhibitor
concentrations after T. DTU01 fermentation of 5 g l-1
xylose in the presence of different concentrations of
the inhibitors furfural (A) and hydroxymethyfurfural
(HMF) (B).
150
S. cerevisae
T. DTU01
S. cerevisae + T. DTU01
Ethanol yield
(g/g total sugars)
0.38
0.29
0.44
Table 1. Comparison of ethanol yields from pretreated rapeseed straw in a batch fermentation if
using S. cerevisae and Thermoanaerobacter DTU01
individually or in a sequential 2-step process.
Conclusions
• The new isolate, Thermoanaerobacter DTU01, could produce the highest ethanol yield from xylose reported so far for a wild type strain, 0.43 g g-1;
• Low amounts of inhibitors seem to be beneficial for the strain; furfural is more toxic than hydroxymethylfurfural (HMF);
• Thermoanaerobacter DTU01 could produce ethanol from all the fractions of pre-treated rapeseed straw;
• A 2-step process with Thermoanaerobacter DTU01 and S. cerevisae was more efficient in producing ethanol from rapeseed straw than the separate
counterparts.