High solid loading enzymatic hydrolysis of various paper wastes
Lei Wang *, Richard Templer ‡ & Richard J. Murphy *
of Biology, Imperial College London, London, SW7 2AZ, UK
Results
Relationship between glucose yield and lignin content
Composition profile
As a potential feedstock for producing bioethanol, paper wastes have the following
advantages:
• Abundance in the UK. The collected paper from waste stream reached 8.1 million
tons in 2009 [1].
• Prices in the range of £30/ton to £45/ton [2].
• GHG emission savings. 82.9 billion litres of waste paper-derived cellulosic
ethanol can be produced globally, replacing 5.36% of gasoline consumption with
GHG emissions savings up to 86.1% [3].
This study of the technological feasibility of producing fermentable sugars from
various paper wastes investigated:
Department of Chemistry, Imperial College London, London, SW7 2AZ, UK
Celluclast 1.5L+Novozyme 188
a
Newspaper
47.20 (0.05)b
7.11 (0.02)
1.90 (0.02)
7.31 (0.01)
1.86 (0.07)
1.06 (0.01)
17.08 (0.43)
3.93 (0.05)
2.13 (0.04)
10.51 (0.11)
100.09
Glucan
Xylan
Galactan
Mannan
Arabinan
ASL c
AIL d
Extractives
CaO
Ash
Total
Used office paper
58.64 (0.05)
14.65 (0.08)
0.00
0.00
0.00
1.41 (0.01)
4.68 (0.29)
1.97 (0.05)
8.12 (0.02)
7.97 (0.08)
97.44
Magazine
35.91 (0.08)
4.72 (0.06)
1.98 (0.02)
5.67 (0.04)
1.82 (0.03)
0.98 (0.03)
13.85 (0.29)
3.45 (0.06)
2.63 (0.04)
30.14 (0.16)
101.15
Cardboard
52.61 (0.06)
8.23 (0.06)
1.89 (0.01)
5.07 (0.01)
1.55 (0.03)
1.59 (0.02)
14.18 (0.19)
2.55 (0.02)
4.20 (0.01)
9.89 (0.07)
101.76
70
Cellic Ctec 1
Glucan conversion efficiency %
Introduction & Motivation
‡
Glucan conversion efficiency %
*Division
60
50
40
30
0
10
20
Lignin content %
30
70
Newspaper
Used office paper
Magazine
Cardboard
E0=12 g/l
E0=11 g/l
E0=10 g/l
60
50
40
30
0
10
20
Lignin content %
Fig. 3. The correlation between glucose yield and lignin content for four types of paper at three different enzyme concentrations for
two enzyme systems
Two enzyme systems were at the same weight concentration loading.
Glucose yield was decreased linearly with increasing lignin content for both enzyme systems.
a All results are presented as percentages of oven dry weight.
b Three replications were performed. Standard errors are in brackets.
c ASL presented acid soluble lignin which was measured using UV-vis at 330 nm determined in-house.
d AIL is acid insoluble lignin.
Comparison of two different enzyme systems
Effect of blending on glucose yields
100
Glucan conversion efficiency %
Methods and Kinetic model
Glucan conversion efficiency %
70
• The detailed compositional analysis
• High solids loading of enzymatic hydrolysis
• Understanding kinetics of enzymatic hydrolysis
• Comparison between two enzyme systems
30
60
50
No blending
5 mins
10 mins
40
30
20
10
Newspaper
Office paper
Cardboard
Magazine
Celluclast 1.5L+ Novozymes
Cellic Ctec
90
80
70
60
50
40
0
5
Enzyme loading (FPU/g glucan)
Used office paper
Glucose concentration (g/l)
Glucose concentration (g/l)
80
60
40
20
60
40
20
20
40
Time (h)
60
60
40
20
20
40
Time (h)
60
Xylose concentration (g/l)
20
15
10
5
0
15
10
5
20
40
Time (h)
60
80
40
Time (h)
60
0
20
40
Time (h)
60
80
60
40
20
0
80
20
40
Time (h)
60
80
25
4
3
2
1
0
Experimental results;
20
40
Time (h)
60
80
15
Acknowledgements
10
The authors wish to thank the Porter Institute (Imperial College) for financial support and Novozymes A/S, Demark for
donation of Cellic Ctec 1 and Lars Saaby Pedersen from Nozoymes A/S for useful discussions on the results.
5
0
Glucan hydrolysis model prediction;
Fig. 2. Kinetics of glucan and xylan hydrolysis for four types of paper using Celluclast 1.5L + Novozymes 188
• Waste paper, as a cellulosic fraction of municipal solid waste, with varied sugar content
from 50% in magazine to 74% in used office paper has great potential as a raw material
to produce fermentable sugars and ethanol.
• A wet blending step prior to enzymatic hydrolysis can increase glucose conversion
efficiency by 5 to 10 percentage points for newspaper e.g. from 48% to 58%.
• Experimental data of high solids loading hydrolysis using two different enzyme systems
was fitted well to glucan and xylan hydrolysis models providing scientific insight and
inputs for industrial process design.
• Glucose yields of papers were found to be inversely proportional to their lignin contents
over the range of 6 to 18% lignin.
• Cellic Ctec 1 had potential for saving total enzyme loadings.
20
0
0
0
0
20
5
20
80
0
0
80
25
25
100
0
0
80
25
Conclusions
Cardboard
80
0
0
Xylose concentration (g/l)
Magazine
100
80
20
Cellic Ctec 1 resulted in higher glucose yield in the range of 5% to 15%.
Cellic Ctec 1 could reduce enzyme dose to obtain the same glucose yield because of its
higher activity (120 FPU/ml) than the other system (95 FPU/ml). This saves 30% enzyme
loading for office paper.
Glucan and xylan hydrolysis model
100
15
Fig. 4. Glucose yield at 72h for four types of paper using two different enzyme systems
The glucose yield was significantly increased at 10 and 15 FPU/ g glucan enzyme loading
potentially because:
• The enzyme absorption is sensitive to particle size in this range of enzyme loading.
• For higher enzyme loading (>20 FPU), the particle size appears to be non-limiting for
hydrolysis efficiency because of the excess of free enzyme.
• For lower enzyme loading (5 FPU), the increase of accessible surface area is not an
advantage due to the limited amount of enzyme applied.
Newspaper
10
E0 g/L
Fig. 1. Enzymatic hydrolysis of newspaper after blending for different periods of time at different enzyme loadings (Celluclast 1.5L +
Novozymes 188 system. Three replications were performed and standard error was shown)
0
A simple correlation between glucan and xylan hydrolysis rate was adopted and
modified to develop xylan hydrolysis model [5]:
30
0
100
A three parameters model involving Langmuir adsorption and second order
enzyme deactivation was adopted [4]. The data fit was modified, using binary
regression (two dimensions).
30 FPU
Glucose concentration (g/l)
The high solids loading 15% (w/w) enzymatic hydrolysis was carried out in a
overhead stirred reactor.
20 FPU
Xylose concentration (g/l)
Blending was performed at 15% (w/w) solids loading in a bench-top blender. Its
effect was evaluated by enzymatic hydrolysis at 5% (w/w).
15 FPU
Glucose concentration (g/l)
Composition of paper materials and enzyme activities were determined following
NREL protocols.
10 FPU
Xylose concentration (g/l)
Paper wastes were collected locally. Celluclast 1.5 L and Novozymes 188 were
purchased (overall activity of the mixture in an activity ratio of 1:1 was 95FPU/ml);
Cellic Ctec 1 (120 FPU/ml) was donated by Novozymes A/S Denmark.
5 FPU
50
Time (h)
100
Xylan hydrolysis prediction
References
[1,2] WRAP, (2010), Market situation report.
[3] Shi et al., (2009), GCB Bioenerg. 1, 317-320.
[4] Shen and Agblevor, (2008), Chem. Eng. Commun.195 (1), 107-112.
[5] Zhang et al. (2009), Biotechnol. Bioeng. 104 (5), 920-931.