CAFI-2
Integration of Leading Biomass Pretreatment Technologies
Informal Project Status Report
Thayer School of Engineering
Dartmouth College
Rajeev Kumar and Charles E. Wyman
May 19, 2005
Tasks performed:
(i)
Enzymatic digestion of dilute acid pretreated corn stover and poplar provided by
NREL.
(ii)
Enzymatic digestion of SO2 pretreated corn stover provided by UBC.
(iii)
Determination of protein content of enzymes from Genencor using BCA and BioRad
protein assay methods.
Enzymatic digestion of dilute acid pretreated corn stover and poplar
The pretreatment conditions, percent glucan in the pretreated solids, yield of glucan
from pretreatment, and percent solids used are summarized in Table 1 for the corn stover and
poplar processed by NREL. Also listed is the shortened sample name along with the
corresponding full sample number below the table that follows the agreed on CAFI approach
to incorporate key features relevant to preparation of these samples.
Table 1. Pretreatment conditions, glucan content, and glucan yields for solids pretreated by
NREL.
Pretreatment conditions
Time
Temp
( min)
( 0C )
Corn stover sample number
CS1
1.5
190
CS2
1.5
180
CS3
1.5
180
Percent
glucan
Percent
yield of
glucan
%
solids
78.20
84.70
93.40
26-28
25-27
30-32
87.90
88.00
75.70
67.00
29-31
29-31
29-31
29-31
Percent
acid
Other
conditions
4.5
3.0
3.0
Mix 2-5
Hot washed
59.5
57.7
59.30
2.0
2.0
2.0
2.0
-----------------
57.32
60.27
54.58
44.26
Poplar sample number
POP1
POP2
POP3
POP4
70
120
70
120
190
190
200
200
Sample numbers and corresponding nomenclature summarizing key conditions:
CS1 = DALW-CSR-190C-1.5m-0.045H2SO4: Dry wt-30% solids-12/9/03-Mix 2:5
CS2 = DALW-CSR-180C-1.5m-0.045H2SO4: Dry wt-30% solids-12/9/03-Mix 2:5
CS3 = DALW-CSR-190C-1.5m-0.045H2SO4: Dry wt-30% solids-12/9/03-Mix 2:5 (Hot
washed)
POP1 = DASE-POP1-190C-70s-0.02H2SO4: Dry wt-30% solids-10/4/04-N-A: G
POP2 = DASE-POP1-190C-120s-0.02H2SO4: Dry wt-30% solids-10/4/04-N-A: G
POP3 = DASE-POP1-200C-70s-0.02H2SO4: Dry wt-30% solids-10/4/04-N-A: G
POP4 = DASE-POP1-200C-120s-0.02H2SO4: Dry wt-30% solids-10/4/04-N-A: G
The yields for enzymatic digestion of the corn stover and poplar solids listed in Table
1 are summarized in Table 2 and 3, respectively, for cellulase loadings of 20 and 50 FPU/gm
original glucan both with and without beta-glucosidase supplementation.
Table 2. Yields from enzymatic digestion of corn stover cellulose in NREL pretreated solids
after 72 hours for cellulase loadings of 20 and 50 FPU/gm glucan in the original feed
without and with beta-glucosidase supplementation.
% yield
Sample
20 FPU/ gm original glucan
50 FPU/ gm original glucan
Without beta-g
With beta-g
Without beta-g
With beta-g
CS1
55.91
55.94
56.17
56.75
CS2
47.11
49.37
51.16
51.30
CS3
67.94
69.41
70.92
71.49
Table 3. Yields from enzymatic digestion of poplar cellulose in NREL pretreated solids
after 72 hours for cellulase loadings of 20 and 50 FPU/gm glucan in the original feed
without and with beta-glucosidase supplementation.
% yield
20 FPU/ gm original glucan
50 FPU/ gm original glucan
Sample
Without beta-g
With beta-g
Without beta-g
With beta-g
POP1
74.02
72.85
83.30
77.74
POP2
61.59
60.62
62.97
70.59
POP3
73.35
77.35
77.88
79.61
POP4
68.45
58.74
69.43
63.42
Summary of initial observations:
(i)
The washed low severity corn stover gave the highest yields.
(ii)
The higher enzyme loadings did not necessarily give the highest ultimate yields.
(iii)
For poplar, pretreatment at low severity, POP-1, gave the highest digestibility, ~ 75
and 84 %, for both enzyme loadings tested.
Enzymatic digestion of SO2 pretreated corn stover
Unwashed SO2 pretreated corn stover from UBC was washed as prescribed by UBC
and analyzed for composition, with the data summarized in Table 4. Cellulase enzyme was
then added to this material at four different loadings without and with beta-glucosidase
supplementation to give the results in Table 5.
Table 4. Composition of corn stover pretreated at 190oC for 5 minutes with 3% SO2 and water
washed (% weight).
%
Acid
Acid
yield
%
Glucan Xylan Arabinan Mannan soluble
insoluble
of
solid
lignin
lignin
glucan
UBC
56.9
11.6
0.25
0.3
1.39
22.4
100
--(n = 6)
(1.0)
(0.05)
(0.02)
(0)
(0.03)
(0.52)
Dartmouth
(n =2)
53.96
11.72
1.78
1.72
1.39
24.8
---
SO2-CSR-190C-5min-3% SO2/solids-4/11/05-N
Table 5. Yields from enzymatic digestion of corn stover cellulose in NREL pretreated
solids after 72 hours for cellulase loadings of 15, 20, 50, and 60 FPU/gm glucan in the
original feed without and with beta-glucosidase supplementation for 1% glucan in 100 ml.
% Yield
Enzyme Loading
Spezyme
Spezyme + β-glucosidase
( FPU/ gm original
(CBU:FPU = 2.0)
glucan)
15
79.4
80.5
20
80.5
81.0
50
85.0
86.1
60
85.8
86.5
Summary of initial observations:
(i)
Yields increased with enzyme loading, but only modestly.
(ii)
Beta-glucosidase supplementation only increased the yields slightly.
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