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(Hemi)-cellulosic Bioethanol
Jan de Bont Detmold, April 15, 2008
Royal Nedalco
• Produces ethanol since 1899
• Currently 3 production locations (2 in The Netherlands; 1 the UK)
• Ethanol produced now mainly for consumption alcohol and other non-fuel purposes
• Strong expansion seen in the market for fuel ethanol (bioethanol)
Second Generation Production Processes:
• Own production locations in Europe
• Involvement in commercial pentosic ethanol production in the USA
Goals of Nedalco for Bioethanol
Central Issues in Bioethanol Production
• Sugar-containing feedstocks that are reliably supplied and are cheaply as well as abundantly available
• Economic processes for the conversion of sugars into bioethanol
Feedstocks and Complexity
MolassesSugar cane,Beet sugar
Wheat,Corn
Starch-containingwheat or cornby-products
Wheat bran,Corn fiber
PretreatmentEnzymes
Special C5-yeast
Wheat straw,Corn stover
Woodymaterials
Complexity
Time2008
First generationfeedstocks
Secondgenerationfeedstocks
Categories of Feedstocks for Bioethanol
Category 1 Sugar and starch streamsSucrose in beet and cane including molassesGlucose from starch in wheat and cornGlucose from starch-containing side streams
Category 2 (Hemi)cellulosic side streams and Dedicated soft biomass(a) Side streams (wheat bran, corn fiber) containing the difficult to degrade polymers hemicellulose(into xylose and arabinose) and cellulose (into glucose) apart from starch.(b) Dedicated soft biomass (grasses, engineered crops) containing difficult to degrade polymers and some lignin
Category 3 Hard biomassWheat straw, corn stover and woody materials containingsubstantial amounts of lignin which is seriously frustrating the hydrolysis of (hemi)cellulose
Lignocellulose utilization: a stepwise feasibility/development
Time
Hard biomass
2008 Commercial Implementation
Complexity
Sugar andstarch streams
(a) Wheat branCorn fiber, etc
Category 1
Category 2 (a and b)
Category 3
First generation Second generation
(b) Dedicatedsoft biomass
Wheat Bran
Wheat and Corn
wheatStarch
Cellulose
Arabinoxylan
other sugars (galactose,glucuronic acid, mannose)Lignin
Protein
Lipid
Ash
wheat bran
corn corn fiber
Integration wheat and ethanol plants
Wheat bran
Dry feed
Wheatprocessing
plant
C-starch Stillage
Ethanol
Alcoholplant
Dryer
Products
Wheat
Simplified Production Process
Physicaland/or
chemicalpretreatment
Enzymatichydolysis
Yeastfermentation Distillation
EthanolCo-products
Feedstock
Major Technological IssuesCategory 2 Feedstocks
1. Pretreatment
2. Hemicellulolytic enzymes commercially available
3. Industrial yeast capable of C5 fermentations
Pretreatment37 °C, Low pH
On SiteEnzyme production
Efficiency hydrolysisapprox. 80 %
Remainingpolymers
Pretreatment and Enzymatic Hydrolysis
Wheat BranHeat-pretreatment lab-scale
1 L reactor
Electric heating, but also steam (20 bar)!-> heating up time: within 5 min to 180 °C
steam (20 bar)through spiral
Before treatment
020406080
100120140160180
0 2 4 6 8 10 12 14 16 18 20 22Time (min)
Tem
pera
ture
(°C
)
start steam through spiral
stop steam
start cold water through spiralstart cold water through spiralExample of heating curve
Wheat BranHeat-pretreatment lab-scale
Wheat Bran: Pretreatment
Pretreatments (20 Experiments):
H2SO4 (%): 0, 1 or 2 %w/w (based on dry weight feedstock)Temp (°C): 120, 140, 160, 180 °CTime (min): 5, 10, 15 minutes
All: 12% dry weight wheat bran in water
Twenty Pretreatments:HMF and Furfural
% H2SO4
T (°C)
t (min)
FurfuralHMF
0
0.5
1
1.5
2
2.5
0 10 10 5 10 15 5 10 5 10 5 10 5 10 15 5 10 5 10 5 10
0 120180 120 140 160 180 120 140 160 180
0 1 2
Am
ount
(g/L
)
confidential
www.itis.gov
Kingdom PlantaeTracheobionta (vascular plants)
Coniferophyta (gymnosperms)
Magnoliophyta (angiosperms)
others
others
Pinopsidaothers
Quercus(Oak)Hard-wood
Liliopsida (monocotyledons) Magnoliopsida (dicotyledons)
Commelinidaeothers
Hamamelidaeothers
Cyperalesothers etc.
Pinus L.(Pine)Soft-wood
etc.
CyperaceaePoaceae (gramineae, grasses)
othersZea L.(corn)
Triticum(wheat)
Pennisetum(grass)
Cat. 3
Cat. 3
Cat. 2 Cat. 2
arabinoxylans
Plants and hemicelluloses
Arabinoxylans and Enzymes
Endo-xylanases : key enzymes
* hindered by the various side-groups linked to xylan-backbone.
Therefore, side-group removing activities are of high importance for complete degradation of corn/ wheat-xylan to (mainly) xylose and arabinose.
Backbone of β-1,4-linked xylosyl residues; arabinosyl residues as side chains:
O O O O O O O O O O O OO O O O O O O
Arabinoxylan -> β-1,4-xylan
Enzymes needed for degradation of wheat xylan:
AXH-d3 (EC 3.2.1.55)
β-1,4-endo-xylanases (EC 3.2.1.8)
O O O O O O O O O O O O
O
O O
β-xylosidase (EC 3.2.1.37) Extra: Feruloyl esterase (EC 3.1.1.73)
xylan-acetylesterase (EC 3.1.1.72)
AXH-s1,2 (EC 3.2.1.55)α-(4-O-methyl)glucuronosidases
xyloseO
arabinose
O glucuronic acid
O-acetyl
O
O
O O O O O
Wheat arabinoxylan and enzymes
Arabinoxylan -> β-1,4-xylan
Enzymes needed for degradation of corn xylan:
AXH-d3 (EC 3.2.1.55)
β-1,4-endo-xylanases (EC 3.2.1.8)
O O O O O O O O O O O O
O
O O
β-xylosidase (EC 3.2.1.37) Extra: Feruloyl esterase (EC 3.1.1.73)
xylan-acetylesterase (EC 3.1.1.72)
(more important than for wheat)
AXH-s1,2 (EC 3.2.1.55)α-(4-O-methyl)glucuronosidases
xyloseO
arabinose
O glucuronic acid
O-acetyl
O
O
β1,3-xylosidase?
O
O
O galactose
α -1,5-arabinofuranosidase?galactosidase + xylosidase?
O
O O O O O OO
Corn arabinoxylan and enzymes
Arabinoxylans and Enzymes
• General aspects arabinoxylans and enzymes
Arabinoxylans from wheat bran
• Arabinoxylans from corn fiber
Twenty Pretreatments:Enzymes and Release Arabinose
% H2SO4
T (°C)
t (min)
Maximum release possible as analyzed after acid hydrolysisReleased after Pretreatment (Pt)Released after Pt + Exp. enzymes + Celluclast + Novozyme188 + AMG + amylase
Released after Pt + same enzymes PLUS protease
0
2
4
6
8
10
12
14
0 10 10 5 10 15 5 10 5 10 5 10 5 10 15 5 10 5 10 5 10
0 120 180 120 140 160 180 120 140 160 180
0 1 2
Ara
bino
se m
onom
er (g
/L)
Twenty Pretreatments:HMF and Furfural
% H2SO4
T (°C)
t (min)
FurfuralHMF
0
0.5
1
1.5
2
2.5
0 10 10 5 10 15 5 10 5 10 5 10 5 10 15 5 10 5 10 5 10
0 120180 120 140 160 180 120 140 160 180
0 1 2
Am
ount
(g/L
)
confidential
Twenty Pretreatments:Enzymes and Release Xylose
% H2SO4
T (°C)
t (min)0
2
4
6
8
10
12
14
16
18
20
0 10 10 5 10 15 5 10 5 10 5 10 5 10 15 5 10 5 10 5 10
0 120 180 120 140 160 180 120 140 160 180
0 1 2
Xylo
se m
onom
er (g
/L)
Maximum release possible as analyzed after acid hydrolysisReleased after Pretreatment (Pt)Released after Pt + Exp. enzymes + Celluclast + Novozyme188 + AMG + amylase
Released after Pt + same enzymes PLUS protease
Arabinoxylans and Enzymes
• General aspects arabinoxylans and enzymes
• Arabinoxylans from wheat bran
Arabinoxylans from corn fiber
Corn versus Wheat Bran
•Comparison in situations of almost no pretreatment•Experimental enzymes + Celluclast + Novozyme188
Release of monomers (%):
Corn Wheat branXylose 18 68 Arabinose 30 45
Why these differences?
O O O O O O O O O O O O
O O O
O
O O O O O OO
O O O O O O O O O O O O
O O O O O O O
Corn versus Wheat Bran
Corn hemicellulose structure:
Calculated from molar composition:Per 100 xyloses: - 66 Arabinoses
- 20 GlcA(me)- 24 Acetyl- 14 Galactoses
Wheat bran hemicellulose structure:
Calculated from molar composition:Per 100 xyloses: - 58 Arabinoses
- 7 GlcA(me)- 7 Acetyl- 5 Galactoses
Corn versus Wheat Bran
Corn hemicellulose structure: Wheat bran hemicellulose structure:
Ara
GlcA(me)AcetylGal
EmptyAra
GlcA(me)Acetyl
Gal
Empty
Consequently, for CORN hemicellulose: Enzymes in removal of glucuronic acid and acetic acid relatively very important
Implications for pretreatment?
Major Technological IssuesCategory 2 Feedstocks
1. Pretreatment
2. Hemicellulolytic enzymes commercially available
3. Industrial yeast capable of C5 fermentations
S.cerevisiae RWB 218
Fermentation of xylose
Xylose Arabinose
Glucose
Fructose
Starch
Cellulose Hemicellulose
Sucrose
Fermentation of Sugars by Saccharomyces cerevisiae
S.cerevisiae RWB 218
Kuyper, M, Toirkens, M.J., Diderich, J.A., Winkler, A.A., Van Dijken, J.P. and Pronk, J.T.
Evolutionary engineering of mixed-sugar utilization by a xylose-fermenting Saccharomyces cerevisiae strain.
FEMS Yeast Research 5, 399-409 (2005).
Key in Xylose-fermenting RWB 218
O
OH
HO
HO
OH
D-xylose
HO
OH
HO
OH
O
D-xylulose
OH
OH
HO
HO
OH
xylitol
HOEthanol
Xylose isomerase
Wheat Bran (SSF) fermentation labscale
Wheat Bran – pretreated; addition of xylose; labscale
Effect addition of xylose on fermentation of wheat bran hydrolysate (10 % dm)
0,0
20,0
40,0
60,0
80,0
100,0
120,0
140,0
160,0
180,0
200,0
0,0 20,0 40,0 60,0 80,0 100,0 120,0Elapsed Time [hours]
Flow
CO
2 [
ml/h
]
Xylose added (52 g/l) Xylose added (78 g/l)
Xylose added (104 g/l)
Xylose added 131 g/l
Xylose added (158 g/l)
Effect addition of xylose on fermentation of wheat bran hydrolysates
0,0
1000,0
2000,0
3000,0
4000,0
5000,0
6000,0
0,0 20,0 40,0 60,0 80,0 100,0 120,0 140,0 160,0
Elapsed Time [hours]
CO
2 flo
w
[m
l]
Pretreated wheat bran hydrolysate; reference
Reference + 52 g/l xylose
Reference + 78 g/l xylose
Reference + 104 g/l xylose
Reference + 131 g/l xylose
19,9 g/l ethanol
44,6 g/l ethanol
57,1 g/l ethanol
66,2 g/l
69,8 g/l ethanol
Wheat Bran – pretreated; addition of xylose; labscale
Wheat Bran at Scale 2 m3
400 kgs wheat branmilling 500 micron 25 w% H2SO4
demi H2O
wheat bran slurry±60ºC - pH 3,0 18% DM
steaminjection
pH 3,0 148ºC 10 min
pretreated wheat branDM 16% ;cooled to±85ºC pH5,3 with KOH α-amylase for 1 hour
α-amylase
2200 l wheat bran slurryDM ±400 kg ;cooled to ±55ºC gluco amylase + otherscooldown to ±32ºC adjust to pH 4,3 with 25 w% H2SO4pitched with 70 l yeast slurry
M M
air input 1320 l/hr
cooling in
coolingout
CO2 out
cooling
pump 4,5 m3/hr
70 l yeast propagationXylose yeast60 g glucose/l 40 g xylose/l
0,4 g DAP/l
12,5 g yeast extract/l pH 4,5 (H2SO4) 32ºC
25 w% H2SO4
enzyms
Wheat Bran at Scale 2 m3
WHEATBRAN
SLURRY18% Dry Weight
PRETREATMENT150 CpH = 3
ENZYMESAmylasesCellulase
Experimental Hemicellulases FERMENTATION
(2100 Liter)
Nedalco Yeast
BIOETHANOLMaterial made accessible to
enzymes
Enzymes liberate free
sugars
Yeast produces
bioethanol
Fermentation 2200L – monomers/ ethanol
0
5
10
15
20
25
30
35
40
45
0 5 10 15 20 25 30 35 40fermentation time (h)
Free
mon
omer
s or
Eth
anol
(g/L
)
Glucose
Ethanol
ArabinoseXyloseFructose
Theory: 32.0 g/L(calculated fromamount of monomersat t0)
confidential
Wheat Bran at Scale 2 m3
Arabinose Fermentation
Based on bacterial enzymes expressed in S. cerevisiae
J. Becker and E. BolesA modified Saccharomyces cerevisiae strain that consumes L-arabinoseand produces ethanolApplied and Environmental Microbiology 69, 4144 (2003)
H.W. Wisselink, M.J. Toirkens, M. del Rosario Franco Berriel, A.A. Winkler, J.P. van Dijken, J.T. Pronk and A.J.A. van MarisEngineering of Saccharomyces cerevisiae for efficient anaerobic alcoholicfermentation of L-arabinoseApplied and Environmental Microbiology, June 2007
Industrial strains
Joint effort required with yeast-producing company
Should result in Industrial Yeasts for the conversion of xylose and/or arabinose
In Conclusion:A few challenges ahead
• Pretreatment
• Enzymatic hydrolysis
• Engineered yeast
• Nutritional value co-products for animal feed
• GMO issues
