Enzymatic saccharification of cellulose in aqueous-ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate-DMSO media

Article abstract of DOI:10.2478/s11696-011-0066-6

Ionic liquid (IL) 1-ethyl-3-methylimidazolium dimethylphosphate ([Emim]DMP) was chosen as an environment-friendly solvent to enzymatically hydrolyze cellulose in situ. Under optimal reaction condition, 80.2 % of cellulose (10 mg mL^-1) were converted to glucose in aqueous-IL-DMSO (?r = 74 : 25 : 1) media at 55.C in 18 h. Finally, fermentability of the recovered hydrolyzates was evaluated using Saccharomyces cerevisiae which is able to ferment hydrolyzates efficiently, the ethanol production was 0.44 g g ^-1 of glucose within 24 h of the process. Such information is vital for the saccharification of more complex cellulose materials and for the fermentation of hydrolyzates into biofuel.

Full text of DOI:10.2478/s11696-011-0066-6

Chemical Papers 65 (6) 792–797 (2011)
DOI: 10.2478/s11696-011-0066-6
ORIGINAL PAPER
Enzymatic saccharification of cellulose in aqueous–ionic liquid
1-ethyl-3-methylimidazolium dimethylphosphate–DMSO media
a
a
c
c
aYu C. He, a,bCui L. Ma*, Dong Q. Xia, Liang Ding, Liang Z. Li, Mu Xian
aCollege of Pharmaceutical and Life Sciences, Changzhou University, Changzhou 213164, China
bChangzhou Kangpu Pharmaceutical Co., Ltd. Changzhou 213172, China
cQingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266071, China
Received 4 April 2011; Accepted 20 May 2011
Ionic liquid (IL) 1-ethyl-3-methylimidazolium dimethylphosphate ([Emim]DMP) was chosen as
an environment-friendly solvent to enzymatically hydrolyze cellulose in situ. Under optimal reac-
tion condition, 80.2 % of cellulose (10 mg mL−1) were converted to glucose in aqueous–IL–DMSO
(ϕr = 74 : 25 : 1) media at 55◦C in 18 h. Finally, fermentability of the recovered hydrolyzates
was evaluated using Saccharomyces cerevisiae which is able to ferment hydrolyzates efficiently, the
ethanol production was 0.44 g g−1 of glucose within 24 h of the process. Such information is vital
for the saccharification of more complex cellulose materials and for the fermentation of hydrolyzates
into biofuel.
c
ꢀ 2011 Institute of Chemistry, Slovak Academy of Sciences
Keywords: ionic liquid, 1-ethyl-3-methylimidazolium dimethylphosphate, cellulose, enzymatic sac-
charification, DMSO, optimization
Introduction
a cumbersome, painstaking and time consuming task.
To eliminate the recovery of IL-treated cellulose and
simplify the entire process for cellulose saccharifica-
tion, one promising strategy is the enzymatic in situ
saccharification of IL-treated cellulose in biocompati-
ble IL–aqueous media. Kamiya et al. (2008) reported
enzymatic saccharification of cellulose in aqueous–IL
[Emim]DEP (ϕr = 1 : 4) media; over 50 % of the
cellulose mass could be converted to glucose in 24 h.
However, in the above aqueous–IL systems, efficiency
of cellulose hydrolysis into glucose is still not high
enough. In-depth studies concerning biocompatibility
of ILs and appropriate reaction media for enzymatic
in situ saccharication are necessary to make hydrolysis
more applicable.
To make cellulosic materials more susceptible to
hydrolysis by cellulases, a pretreatment process reduc-
ing the cellulose crystallinity and increasing the cellu-
lose porosity is needed (Chandra et al., 2007; Peterson
et al., 2007; Saha et al., 2005). Different pretreatment
methods have been used for the pretreatment of cel-
lulosic materials (Dadi et al., 2006; Hendriks & Zee-
man, 2009; Moulthrop et al., 2005; Remsing et al.,
2008; Yán˜ez et al., 2006) since regenerated cellulose
with amorphous structure provides more surfaces for
enzymes to attack on. In recent years, ionic liquid (IL)
was found to be a stable and effective solvent for dis-
solving and pretreating cellulose (Dadi et al., 2006;
Heinze et al., 2001; Moulthrop et al., 2005; Zhao et
al., 2009). However, many ILs induce different degrees
of cellulase inactivation (Zhao et al., 2008). A recovery
process of the IL-treated cellulose was required prior
to enzymatic saccharification of cellulose, which was
In our study, biocompatible IL [Emim]DMP was
used for the in situ saccharification process. Scan-
ning electron microscopy (SEM), Fourier transformed
IR (FTIR), and X-ray diffraction (XRD) were ap-
plied to establish possible means for the enzymatic hy-
*Corresponding author, e-mail: macuiluan@163.com

Y. C. He et al./Chemical Papers 65 (6) 792–797 (2011)
793
drolysis enhancement. After optimization of the reac-
tion parameters, an in situ saccharification process in
aqueous–IL [Emim]DMP–DMSO media was started.
Moreover, fermentability of glucose recovered from the
hydrolyzates was investigated.
Fermentability of the recovered hydrolyzates was
evaluated using the ethanol producing strain S. cere-
visiae. The inoculum was prepared by transferring a
loop of cells of S. cerevisiae into 20 mL of the YEPD
medium (5.0 g L−1 of yeast extract, 10.0 g L−1 of pep-
tone, and 10.0 g L−1 of D-glucose) and its incubation
at 30◦C for 24 h. The cells were harvested by cen-
trifugation (8000 min−1, 10 min), suspended in steril-
ized water and used in the following ethanol fermen-
tation; the cells’ suspension (0.2 mL) was inoculated
into 20 mL of the fermentation medium (glucose in hy-
drolyzates: 25.0 g L−1, MgSO4: 0.20 g L−1, NH4Cl: 1.0
g L−1, and KH2PO4: 2.0 g L−1, pH 6.0) in a 100 mL
flask. The fermentation was carried out at 30◦C un-
der semi aerobic conditions. Control experiment was
conducted using 25.0 g L−1 of D-glucose as the carbon
source in the fermentation.
Cellulase activity was determined by the standard
filter paper assay and expressed as filter paper units
per gram of glucan (FPU) (Dadi et al., 2006). One
FPU is defined as the enzyme releasing 1 µmol of glu-
cose equivalents per minute from the filter paper. The
released glucose was assayed using a commercial anal-
ysis kit containing glucose oxidase (Institute of Bio-
logical Products, Shanghai, China).
Experimental
Avicel PH-101 (cellulose) was purchased from
Fluka (Buchs, Switzerland). Cellulase was kindly do-
nated by Genencor (Shanghai, China). The ethanol
producing strain S. cerevisiae was preserved by our
laboratory. All other reagents and chemicals used were
also from commercial sources and of reagent grade.
Stock solution of cellulose was prepared by adding
cellulose to IL [Emim]DMP for 20 min at 55◦C. Then,
acetate acid-sodium acetate buffer (50 mM, pH 5.0)
was added to make a total 1 mL solution; water-
insoluble fractions (i.e., regenerated cellulose) were
formed after an addition of the aqueous buffer. After
dispersing the mixture, enzymatic reaction was initi-
ated by an addition of 3 mg mL−1 of cellulase to an
aqueous–IL mixture containing 0–100 % (ϕr) of IL.
The final concentration of IL-treated cellulose was 10
mg mL−1. The enzymatic saccharification of cellulose
was carried out at 55◦C and 160 min−1
.
Biomass concentrations were estimated using a
spectrophotometer at 600 nm by measuring optical
density of the cultures. Glucose, xylose, galactose, and
arabinose were assayed by ion chromatography (ICS-
3000, Dionex Corporation, Sunnyvale, CA, USA). The
ion moderated partition chromatography sugar col-
umn PA10 was employed for assaying these monosac-
charide. The samples were eluted with 75 mM NaOH
at the flow rate of 1.0 mL min−1. The injection volume
was 1 mL, and the observed pressure drop was 18.6
MPa. Ethanol was analyzed by HPLC equipped with
a HPX-87H column (Bio-Rad, Shanghai, China) at
65◦C eluted with 10 mM sulfuric acid at the flow rate
of 0.8 mL min−1 and monitored using a RID-10A de-
tector (Shimadzu Co., Japan). Fourier transformed IR
(FTIR) was used to assay the IL [Emim]DMP-treated
celluloses. Spectra (4000–800 cm−1) were recorded
with the resolution of 4 cm−1 and 64 scans per sam-
ple. About 2.5 mg samples were prepared by mixing
with 120.0 mg of spectroscopic grade KBr and were
pressed in a standard device using the pressure of 41.4
MPa to produce 13 mm diameter pellets. The back-
ground spectrum of pure KBr was subtracted from
that of the sample spectrum. Scanning electron mi-
croscopy (SEM) (Hitachi S-4800, Japan) was used to
assay the IL [Emim]DMP-treated celluloses. The sam-
ples were coated with a thin gold layer using a vac-
uum sputter-coater to improve the conductivity of the
samples and thus the quality of the SEM images prior
to the analysis. SEM operated at 5 keV was used to
image the cellulose samples. X-ray diffraction (XRD)
(Bruker D8 ADVANCE, Germany) was used to as-
say IL [Emim]DMP-treated cellulose. Samples were
To investigate the effects of organic solvent addi-
tives on cellulase activity, enzymatic reaction was ini-
tiated by an addition of 3.0 mg mL−1 of cellulase to
an aqueous–IL mixture containing 10 mg mL−1 of IL-
treated cellulose, 25 % (ϕr) of IL and 0.5 % (ϕr) of
different organic solvents. Enzymatic hydrolysis was
run for 1 h in aqueous–IL [Emim]DMP–organic sol-
vent (ϕr = 74.5 : 25 : 0.5) media at 55◦C and 160
min−1. To investigate the effects of DMSO on enzy-
matic hydrolysis of cellulose, enzymatic reaction was
initiated by an addition of 3.0 mg mL−1 of cellulase to
an aqueous–IL–DMSO mixture containing 25 % (ϕr)
of IL and 0–25 % (ϕr) of DMSO. Concentration of IL-
treated cellulose was 10 mg mL−1. Finally, enzymatic
hydrolysis was run for 18 h in a shaker at 55◦C and 160
min−1. To investigate the effects of cellulase concen-
trations on cellulose saccharification, enzymatic reac-
tion was initiated by an addition of 1.0–8.0 mg mL−1
of cellulase to an aqueous–IL–DMSO (ϕr = 74 : 25 :
1) mixture containing 10 mg mL−1 of IL-treated cel-
lulose. Enzymatic hydrolysis was run for 1–12 h in a
shaker at 55◦C and 160 min−1
.
After enzymatic hydrolysis of cellulose, the mix-
ture of IL and hydrolyzates from enzymatic in situ hy-
drolysis of cellulose was filtered and the IL and sugars
were separated in a column filled with neutral Al2O3
according to recently published literature (Xian et al.,
2009). Isolated yields of IL [Emim]DMP and glucose
in hydrolyzates were 96.8 % and 98.7 %, respectively.
Then, the hydrolyzates (recovered sugars) were used
in ethanol fermentation immediately without further
purification.

794
Y. C. He et al./Chemical Papers 65 (6) 792–797 (2011)
Fig. 1. SEM micrographs of untreated cellulose (A) and IL-treated cellulose (B).
Table 1. Infrared ratios expressed as crystallinity indexes of
regenerated cellulose; from FTIR spectra, two in-
frared ratios, LOI and TCI, were calculated (Zhao
et al., 2009): (1) α1437cm−1 /α899cm−1 , referred to as
the crystallinity index or lateral order index (LOI);
(2) α1437cm−1 /α899cm−1 , known as the total crys-
tallinity index (TCI)
Cellulose
LOI
TCI
Untreated cellulose
Cellulose treated by IL at 55◦C
1.16
1.05
1.00
0.96
Wawenumber/cm–1
scanned by XRD over the angular range of 5.0–60◦,
2θ, in continuous scan mode.
Fig. 2. FTIR spectra of untreated cellulose (a) and IL-treated
cellulose (b).
Results and discussion
Pretreatment of cellulose with IL [Emim]DMP
and enzymatic saccharification of cellulose in
aqueous–IL [Emim]DMP media
a
Encouraged by recent findings that show ILs con-
taining alkylphosphate anions as capable of dissolv-
ing cellulose (Kamiya et al., 2008), the solubility of
one kind of IL [Emim]DMP has been proved to be
6.9 % at 55◦C. To visualize the changes of cellulose
structure after its pretreatment with IL [Emim]DMP
for 20 min at 55◦C, the FTIR, XRD, and SEM im-
ages of IL-treated cellulose were recorded. As shown
in Table 1, LOI of IL-treated cellulose significantly
decreased, from 1.16 to 1.05, and TCI of cellulose de-
creased from 1.00 to 0.96. As shown in Fig. 1, SEM
micrographs of IL-treated cellulose are different than
that of the untreated one. It is evident that the fibers
were partially disrupted. Probably during the regener-
ation process, the rapid precipitation with water pre-
vented the IL-treated cellulose from restructuring into
its original crystalline structure (Mikkola et al., 2007).
Based on the FTIR and XRD analysis (Figs. 2 and 3),
b
2θ/°
Fig. 3. XRD micrographs of untreated cellulose (a) and IL-
treated cellulose (b).
the IL-treated cellulose, lost its crystalline structure
and assumed a more amorphous form. Consequently,
the IL-treated cellulose with its amorphous structure
provided more surfaces for enzymes to attack on.
To demonstrate the efficiency of cellulose conver-

Y. C. He et al./Chemical Papers 65 (6) 792–797 (2011)
795
8
6
4
2
0
160
120
80
40
0
l
e
e
F
M
F
o
O
n
n
i
n
S
H
o
d
i
a
T
t
N
D
M
r
u
y
D
B
P
-
t
r
e
0
5
10
15
20
25
t
Solvent
Time/h
Fig. 5. Effect of organic solvent on cellulase activity. Condi-
tions: 10 mg mL−1 of IL-treated cellulose, 25 % (ϕr)
of [Emim]DMP, 0.5 % (ϕr) of organic solvent, 3.0
mg mL−1 of cellulase, hydrolysis run for 1 h at 55◦C
and pH 5.0. All experiments were performed in tripli-
cate. Error bars show the standard deviation of tripli-
cate measurements.
Fig. 4. Time course of the enzymatic hydrolysis of cellulose in
different aqueous–IL systems. Conditions: 10 mg mL−1
of cellulose, different concentrations of [Emim]DMP, 3.0
mg mL−1 of cellulase, hydrolysis run for 24 h at 55◦C
and pH 5.0. ( ) – in aqueous media, untreated cellu-
•
lose, ( ) – in IL–aqueous media (ϕr = 1 : 3), IL-treated
cellulose, (ꢀ) – in IL–aqueous media (ϕr = 1 : 1), IL-
treated cellulose.
pretreatment process eliminated the need for regen-
erated cellulose recovery and it could be carried out
under mild conditions. Also, IL [Emim]DMP could be
chosen as a biocompatible IL for enzymatic in situ
saccharification of cellulose.
sion to glucose in aqueous–IL media, time courses of
enzymatic saccharification of IL-dissolved cellulose in
different aqueous–IL [Emim]DMP mixtures were mon-
itored (Fig. 4). After the hydrolysis of cellulose for 24 h
in aqueous–IL [Emim]DMP (ϕr = 1 : 3) media, the re-
action solution became clear and 7.06 mg mL−1 of glu-
cose were obtained (starting amount of 10 mg mL−1);
glucose formation in the aqueous–IL media was ap-
proximately two fold higher than that of the aqueous
media without IL, indicating that the IL was highly
biocompatible with the in situ saccharification pro-
cess. The above results are similar to those obtained
in the aqueous–[Emim]DEP (ϕr = 1 : 4) media in a
former study (Kamiya et al., 2008). That is, the con-
version of cellulose to glucose was preferred at the IL
[Emim]DMP to water ratio of 1 : 3 (ϕr). Further in-
crease in the IL concentration would lead to a dra-
matic decrease in the activity of cellulase and the yield
of glucose (data not shown). At the IL [Emim]DMP
to water ratio of 1 : 1 (ϕr), 1.04 mg mL−1 of glucose
was obtained from the hydrolysis of cellulose (starting
amount of 10 mg mL−1) after 24 h.
Based on the above data, it can be concluded that
the intact structure of cellulose was disrupted by the
IL [Emim]DMP pretreatment at 55◦C and resulted in
a porous and amorphous regenerated cellulose that
greatly enhanced enzymatic hydrolysis in aqueous–IL
media. In previous reports (Dadi et al., 2006), higher
pretreatment temperature (≥ 100◦C) was required.
Moreover, a following cumbersome recovery process
for the regeneration of cellulose produced by cellulose
pretreatment with ILs prior to enzymatic saccharifi-
cation was also needed. In our study, the low pre-
treatment temperature of 55◦C, just around the op-
erative temperature range for cellulase, was employed
in the dissolving and pretreatment of cellulose. This
Optimization of enzymatic saccharification
of cellulose conditions in aqueous–IL
[Emim]DMP–organic solvent media
In order to obtain a high saccharification rate,
it was necessary to develop an appropriate reac-
tion system for enzymatic saccharification of cellu-
lose. Organic solvent can enhance the cellulase activ-
ity (Lucas et al., 2001) and aqueous–IL–organic sol-
vent media can be effectively used in the saccharifica-
tion process. In our study, 2-methylpropan-2-ol, DMF,
DMSO, pyridine, and THF (ϕr = 0.5 %) were added
into the aqueous–IL [Emim]DMP media, respectively.
As shown in Fig. 5, DMF, 2-methylpropan-2-ol, and
DMSO enhanced the cellulase activity while THF and
pyridine resulted in its significant decrease. Among
these organic solvents, DMSO (ϕr = 0.5 %) enhanced
the cellulase activity 1.4 fold and thus was chosen as
an appropriate organic additive.
Furthermore, the effects of different concentrations
of DMSO, varied from 0 % to 25 % (ϕr), in the
aqueous–IL [Emim]DMP media were investigated. As
shown in Fig. 6, DMSO at the concentrations of 0.5–
2.0 % (ϕr) enhanced the cellulase activity, however,
4 % (ϕr) of DMSO significantly reduced the cellu-
lase activity. At the addition of DMSO into the enzy-
matic hydrolysis media at the concentrations of 0 %,
0.5 %, 1 %, 2 %, and 4 % (ϕr), conversions of cellu-
lose to glucose obtained in 18 h were 69.3 %, 73.6 %,
80.2 %, 62.4 %, and 44.7 %, respectively. It is obvious
that 1 % (ϕr) of DMSO effectively increases the cel-
lulase activity and the yield of glucose in aqueous–IL

796
Y. C. He et al./Chemical Papers 65 (6) 792–797 (2011)
80
60
40
20
0
30
25
20
15
10
5
8
6
4
2
0
0
3
6
9
12
15
18
0
Ti m e / h
0
5
10
15
20
25
30
35
Time/h
Time/h
Fig. 6. Time course of enzymatic hydrolysis of cellulose in
aqueous–IL–DMSO media with different concentration
of DMSO. Conditions: 10 mg mL−1 of IL-treated cellu-
lose, 25 % (ϕr) of [Emim]DMP, 0–25 % (ϕr) of DMSO,
3.0 mg mL−1 of cellulase, hydrolysis run for 18 h at
Fig. 8. Time course of recovered hydrolyzates fermentation by
S. cerevisiae. Fermentation was carried out at 30◦C
under semi aerobic conditions. Ethanol fermentation
medium: glucose in hydrolyzates (or pure glucose): 25.0
g L−1; MgSO4: 0.20 g L−1; NH4Cl: 1.0 g L−1; and
KH2PO4: 2.0 g L−1, pH 6.0. All experiments were per-
formed in triplicate. Error bars show the standard de-
viation of triplicte measurements. (ꢀ) – Glucose, hy-
drolyzate; (ꢂ) – glucose, control; ( ) – OD600, hy-
55◦C and pH 5.0. ( ) – 0 % DMSO; ( ) – 0.5 % DMSO;
•
(ꢀ) – 1 % DMSO; (ꢁ) – 2 % DMSO; (ꢂ) – 4 % DMSO;
( ) – 10 % DMSO; ( ) – 25 % DMSO.
◦
drolyzate; ( ) – OD600, control; ( ) – ethanol, hy-
drolyzate; ( ) – ethanol, control.
•
200
150
100
50
15
12
9
◦
charification of the IL-treated cellulose, the concen-
trations of glucose, xylose, galactose, and arabinose in
hydrolyzates were 8.02 mg mL−1, 1.01 mg mL−1, 0.60
mg mL−1, and 0.21 mg mL−1, respectively.
6
3
0
0
Based on the above data, optimal enzymatic hy-
drolysis conditions were obtained. The aqueous–IL
[Emim]DMP–DMSO (ϕr = 74 : 25 : 1) media were
used as the reaction media. After being hydrolyzed
by 3 mg mL−1 of cellulase for 18 h at 55◦C and 160
min−1, the conversion of cellulose to glucose reached
80.2 %. A high effective enzymatic in situ saccharifi-
cation process with phosphate based IL [Emim]DMP
eliminating the need to recover regenerated cellulose,
with the conversion of cellulose to glucose of over 80 %
(ϕr), has been developed This process can be useful in
integrated bioprocesses such as bioethanol production
from cellulosic materials.
1
2
3
4
6
8
Concentration of cellulase/(mg mL−1
)
Fig. 7. Effect of cellulase concentration. Conditions: 10 mg
mL−1 of IL-treated cellulose, 25 % (ϕr) of [Emim]DMP,
1.0–8.0 mg mL−1 of cellulase, hydrolysis run at 55◦C
and pH 5.0. (ꢁ) – glucose conversion for 18 h; (white
bar) – relative activity. All experiments were performed
in triplicate. Error bars show the standard deviation of
triplicate measurements.
[Emim]DMP–DMSO media (Fig. 3). Therefore, 1 %
(ϕr) of DMSO was added into the hydrolysis media
during the saccharification of cellulose.
Fermentability of recovered hydrolyzates from
enzymatic hydrolysis of cellulose in aqueous–
IL [Emim]DMP–DMSO media
In order to enhance the conversion of cellulose to
glucose, the effect of cellulase concentration was also
investigated. As shown in Fig. 7, the conversion of cel-
lulose to glucose increased markedly, from 1 mg mL−1
to 3 mg mL−1 in 18 h, with the cellulase concentration
and the corresponding maximal conversion reached
80.2 %. Further increase of cellulase concentration
from 3 mg mL−1 to 8 mg mL−1 did not cause any ob-
vious change in the conversion. Obviously, an optimal
enzyme concentration for any enzymatic reaction can
be found. Considering the enzyme cost, 3.0 mg mL−1
was chosen as the optimal cellulase concentration in
this reaction media. Using ion chromatography for as-
saying hydrolyzates obtained from the enzymatic sac-
Fermentability of the recovered hydrolyzates con-
taining glucose was evaluated using the ethanol pro-
ducing strain S. cerevisiae. Fermentation profiles are
presented in Fig. 8. The initial concentration of 25.0
g L−1 to 0.37 g L−1 of glucose in the hydrolyzates
was consumed within 32 h. After 24 h of fermenta-
tion, the ethanol production was 0.44 g g−1 of glu-
cose, which represents 86.1 % of the theoretical yield.
Fermentation was also conducted with pure glucose as
the control sample. These results are similar to those
reported in recent works on fermentation of recov-

Y. C. He et al./Chemical Papers 65 (6) 792–797 (2011)
797
ered hydrolyzates obtained from aqueous media with-
out ILs (Jeihanipour & Taherzadeh, 2009), indicat-
ing that the recovered hydrolyzates obtained from the
aqueous–IL [Emim]DMP–DMSO media do not have
any negative effects on the cell growth and ethanol
production. Although this fermentation process was
not optimized, potential application of recovered hy-
drolyzates was demonstrated in our case.
Hendriks, A. T. W. M., & Zeeman, G. (2009). Pretreatments
to enhance the digestibility of lignocellulosic biomass. Biore-
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05.027.
Jeihanipour, A., & Taherzadeh, M. J. (2009). Ethanol produc-
tion from cotton-based waste textiles. Bioresource Technol-
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Kamiya, N., Matsushita, Y., Hanaki, M., Nakashima, K.,
Narita, M., Goto, M.,
& Takahashi, H. (2008). Enzy-
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and Food Chemistry, 49, 79–85. DOI: 10.1021/jf000916p.
Mikkola, J.-P., Kirilin, A., Tuuf, J.-C., Pranovich, A., Holm-
bom, B., Kustov, L. M., Murzin, D. Y., & Salmi, T. (2007).
Ultrasound enhancement of cellulose processing in ionic
liquids: from dissolution towards functionalization. Green
Chemistry, 9, 1229–1237. DOI: 10.1039/b708533h.
Moulthrop, J. S., Swatloski, R. P., Moyna, G., & Rogers, R.
D. (2005). High-resolution 13C NMR studies of cellulose and
cellulose oligomers in ionic liquid solutions. Chemical Com-
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Thomsen, A.-B. (2007). Potential bioethanol and biogas pro-
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Remsing, R. C., Hernandez, G., Swatloski, R. P., Massefski, W.
W., Rogers, R. D., & Moyna, G. (2008). Solvation of carbo-
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Saha, B. C., Iten, L. B., Cotta, M. A., & Wu, Y. V. (2005).
Dilute acid pretreatment, enzymatic saccharification and fer-
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40, 3693–3700. DOI: 10.1016/j.procbio.2005.04.006.
In our study, IL [Emim]DMP showed favorable sol-
ubility with cellulose and biocompatibility with cel-
lulase. Thus, the novel reaction system involving an
aqueous–IL [Emim]DMP–DMSO (ϕr = 74 : 25 : 1)
mixture was chosen for enzymatic saccharification of
cellulose. After optimization of the reaction param-
eters, the conversion of cellulose to glucose reached
80.2 %. Furthermore, fermentability of the recovered
hydrolyzates was evaluated using Saccharomyces cere-
visiae. This microbe is able to ferment hydrolyzates
to ethanol without negative effects. In summary, our
work presents the IL [Emim]DMP as a promising sol-
vent for enzymatic in situ hydrolysis of cellulose in
aqueous–IL [Emim]DMP–DMSO media; however, its
cost is very high and further study on this subject is
needed.
Acknowledgements. This work was financially supported
by the Natural Foundation of Guangxi (No. 0991001), the
Talent Introduction Foundation of the Changzhou University
(No. ZMF10020077), University student’s Science & Technol-
ogy Creation Foundation of the Changzhou University, and the
Open Funding Project of the State Key Laboratory of Bioreac-
tor Engineering, East China University of Science and Tech-
nology.
Xian, M., Li, L., He, Y., Tan, W., Li, Q., & Yang, F. (2009).
Chinese Patent No. 200910093300.8. Shanghai, China: China
Patent & Trademark Office.
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