Enhancement of activity and reusability of lipase immobilized on magnetic mesoporous silica for the resolution of racemic secondary alcohols

Article abstract of DOI:10.1002/jccs.201800193

Magnetic mesoporous silica (MMS) composites with an average mesopore size (~2.98 nm), large surface area (404–442 m²/g), and high saturated magnetization (17.7–33.5 emu/g) were successfully prepared by hydrothermal crystallization in the presence of monodisperse Fe₃O₄ microspheres. The as-synthesized composites served as supports for lipase from Burkholderia cepacia (BCL) immobilization in isooctane via interfacial activation and were then employed as biocatalysts for the transesterification resolution of racemic aromatic secondary alcohols to synthesize chiral intermediates. The catalytic performance of the immobilized BCL (BCL/MMS) was notably improved compared to that of the non-immobilized BCL, with the total conversion and enantiomeric excess reaching 50 and 99% of the maximum theoretical values, respectively. Furthermore, the magnetic BCL/MMS possessing the same textural properties and enzyme loading exhibited decreasing catalytic capability as their saturated magnetization value increased. Moreover, BCL/MMS could also be readily recycled from the reaction system by applying an external magnetic field so as to facilitate its reuse up to five cycles with retaining up to 90% of the initial activity. Its high activity, easy recovery, and excellent operational stability make the BCL/MMS a potential green catalyst for the synthesis of optically active intermediates.

Full text of DOI:10.1002/jccs.201800193

Received: 11 June 2018
Revised: 17 September 2018
Accepted: 8 October 2018
DOI: 10.1002/jccs.201800193
A R T I C L E
Enhancement of activity and reusability of lipase immobilized
on magnetic mesoporous silica for the resolution of racemic
secondary alcohols
1
1
2
2
2
Ping Xue | Chun-Miao Hu | Xiang-Hui Yan | Guo-Li Fang | Hong-Fang Shen
1
State Key Laboratory of High-efficiency
Magnetic mesoporous silica (MMS) composites with an average mesopore size
(~2.98 nm), large surface area (404–442 m /g), and high saturated magnetization
Utilization of Coal and Green Chemical
2
Engineering, College of Chemistry & Chemical
Engineering, Ningxia University, Yinchuan, China
(17.7–33.5 emu/g) were successfully prepared by hydrothermal crystallization in
2
North Minzu University, Yinchuan, China
the presence of monodisperse Fe O microspheres. The as-synthesized composites
3
4
Correspondence
served as supports for lipase from Burkholderia cepacia (BCL) immobilization in
isooctane via interfacial activation and were then employed as biocatalysts for the
transesterification resolution of racemic aromatic secondary alcohols to synthesize
chiral intermediates. The catalytic performance of the immobilized BCL
Ping Xue, State Key Laboratory of High-efficiency
Utilization of Coal and Green Chemical
Engineering, College of Chemistry & Chemical
Engineering, Ningxia University, Yinchuan,
China.
(BCL/MMS) was notably improved compared to that of the non-immobilized
Email: ping@nxu.edu.cn
Xiang-Hui Yan, North Minzu University,
Yinchuan 750021, China.
BCL, with the total conversion and enantiomeric excess reaching 50 and 99% of
the maximum theoretical values, respectively. Furthermore, the magnetic
BCL/MMS possessing the same textural properties and enzyme loading exhibited
decreasing catalytic capability as their saturated magnetization value increased.
Moreover, BCL/MMS could also be readily recycled from the reaction system by
applying an external magnetic field so as to facilitate its reuse up to five cycles with
retaining up to 90% of the initial activity. Its high activity, easy recovery, and
excellent operational stability make the BCL/MMS a potential green catalyst for
the synthesis of optically active intermediates.
Email: yanxianghui@tsinghua.org.cn
Funding information
National Natural Science Foundation of China,
Grant/Award Number: 21663020
KEYWORDS
enantioselectivity, immobilized lipase, magnetic mesoporous silica, racemic
secondary alcohols, transesterification resolution
1
| INTRODUCTION
contamination of the products, thus impeding their further
[
6,7]
industrial application.
If the lipase is immobilized, the
In recent years, enzymatic catalysis has attracted extensive
attention as an alternative method for the green synthesis of
fine chemicals, pharmaceutical intermediates, and food
employed supports can permit the enzyme molecules to fully
disperse in insoluble hydrophobic organic media, thus avoid-
ing the aggregation of the hydrophilic protein molecules,
which increases accessibility to the substrate. The interaction
between the lipase and the support can cause the opening of
the lid to yield the active conformation. Multipoint attach-
ment of enzyme molecules on the support can also enhance
a rigidification of the enzyme structure and maintain the con-
formation unaltered. Therefore, immobilization of lipases on
[
1–3]
ingredients.
For example, lipases were employed as bio-
catalysts for the chiral resolution of racemic secondary alco-
[
4,5]
hols to prepare optically active alcohols and esters.
However, free lipases often undergo easy inactivation when
exposed to external conditions, and there are difficulties in
their recovery and reuse, which lead to high cost and
©
2018 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J Chin Chem Soc. 2018;1–7.
http://www.jccs.wiley-vch.de
1

2
XUE ET AL.
suitable supports is regarded as a convenient way to improve
2 | RESULTS AND DISCUSSION
.1 | Characterization of MMS-x
the enzyme’s activity and stability and to realize its easy
[
3,8–11]
recovery and reuse.
2
Great efforts have been made to design a variety of sup-
port materials for lipase immobilization, such as inorganic
2
.1.1 | SEM analysis
[
3,11–14]
[15,16]
SEM revealed that the products synthesized by the sol-
vothermal approach were monodisperse nanoparticles with a
narrow size distribution in the range ~310–570 nm (inset in
Figure 1). After these nanoparticles were embedded through
the hydrothermal crystallization with tetraethyl orthosilicate
materials,
inorganic or inorganic composites,
polymeric materials,
organic-
and others
[
17,18]
[19,20]
with different immobilization strategies, including physical
adsorption, covalent attachment, entrapment or encapsula-
[21]
tion, and cross-linking.
Recently, magnetic mesoporous
(TEOS) and cetyltrimethylammonium bromide (CTAB) as
silica (MMS) nanocomposites were widely explored for
lipase immobilization and their further applications because
of their tunable pore size, high surface area, chemically mod-
ifiable surface, fast mass transfer, low cytotoxicity, excellent
the silicon source and structure-directing agent, respectively,
the particles aggregated severely and their morphology
became irregular regardless of the amount of added nanopar-
ticles, as can be observed in Figure 1.
[22–29]
thermal stability, and easy recovery and reuse.
Such
distinct properties are favorable for enzymatic catalysis
when using the MMS as the supporting material. However,
to our best knowledge, most previous reports focused on the
enzyme immobilization capacities and hydrolytic activity,
while there have been few studies dealing with the issue of
the catalytic properties of lipase from Burkholderia cepacia
2
.1.2 | XRD analysis
Low-angle XRD patterns of the MMS-x are shown in
Figure 2a. In the case of the two samples (x = 0.075, 0.10),
three diffraction peaks, assigned to the (100), (110), and
(200) diffractions, reflect an ordered, two-dimensional, hex-
[
32]
agonal mesostructure.
However, the widening of the
(BCL) immobilized on MMS for kinetic resolution of race-
(
(
(
100) diffraction peaks, the weak intensity of the (110) and
200) secondary diffraction peaks, and the absence of the
210) diffraction peaks suggest that the mesoporous structure
mic aromatic secondary alcohols. As is well known, the
introduction of Fe O is mainly responsible for magnetic
3
4
separation. Beyond that, does Fe O have other functions,
3
4
is not long-range-ordered. As the amount of nanoparticles
increased (x = 0.125, 0.25), the high-intensity diffraction
peaks of (100) were still observed but the secondary diffrac-
tion peaks tended to disappear, which indicated that the
nanoparticle content did not disturb the generation of the
mesoporous structure but had a small impact on the long-
range order. Figure 2b shows the wide-angle XRD patterns
for instance, does it influence the texture parameters of
MMS and the catalytic performance of its corresponding
immobilized lipase?
As for BCL, it is mainly applied to transesterification
[11]
resolution reactions in organic media. The optically active
enantiomers of aromatic secondary alcohols could be
obtained from BCL-catalyzed kinetic resolution and used as
essential chiral building blocks and synthetic intermediates
ꢀ
of the MMS. The broad peaks at around 2θ = 23 in the pat-
[
30,31]
terns for all samples are attributed to the formation of amor-
in fine chemicals, pharmaceuticals, and other fields.
ꢀ
ꢀ
phous silica. The diffraction peaks at 2θ = 18.18 , 30.04 ,
3
Here we report the synthesis of MMS composites carried out
by means of a solvothermal method together with hydrother-
mal crystallization followed by immobilization of BCL on
them, implemented in a low aqueous organic biphasic sys-
tem. These MMS materials were characterized by scanning
electron microscopy (SEM), powder X-ray diffraction
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
5.40 , 43.00 , 53.40 , 56.94 , and 62.54 match very well
with the characteristic peaks, indexed to diffraction peaks of
(XRD), nitrogen adsorption–desorption analysis, and vibrat-
ing sample magnetometry. Then, the catalytic activity of the
obtained immobilized lipase (BCL/MMS) was measured
using kinetic transesterification resolution of racemic aro-
matic secondary alcohols in an organic solvent as model
reactions. And the effect of the embedded Fe O content on
3
4
the catalytic activity of the BCL/MMS was also investigated.
As a consequence, it is revealed that the introduction of
Fe O within a certain mass range had little effect on the tex-
3
4
tural properties of the MMS but had a profound influence on
the catalytic activity such that an excessive amount of Fe O4
3
lowered the reaction rate. Our results also indicate that
BCL/MMS composites are far superior to non-immobilized
BCL in catalytic activity and could be fairly easily recycled.
FIGURE 1 SEM images of Fe O and MMS-x (x = 0.075, 0.10, 0.125,
and 0.25)
3 4

XUE ET AL.
3
FIGURE 3
N
2
adsorption/desorption isotherms and pore size distribution
curves of MMS-x
From Table 1, it can be noticed that the average pore size
is the same (~2.9 nm) for samples with different Fe O con-
3
4
tents and that the pore volumes and specific surface areas are
remarkably close as well, providing a chance to subse-
quently specially investigate the effect of the Fe O content
3
4
on the catalytic performance of MMS-x in the chiral resolu-
tion of secondary alcohols by avoiding interference from the
texture properties.
2
.1.4 | Vibrating sample magnetometer analysis
Figure 4 shows the field-dependent magnetization curves of
MMS-x (x = 0.075, 0.10, 0.125, and 0.25) measured at
room temperature. All the curves present very small hystere-
sis loops, which is a typical feature of paramagnetism, indi-
cating that their separation in solution can be easily
controlled by magnetic fields. The saturation magnetization
value of the MMS-x, also summarized in Table 1, increases
from 11.9, 17.7, 21.7, to 33.5 emu/g with the increase in the
added Fe O content from 0.075 to 0.25 g, which represent
FIGURE 2 Small-angle (a) and wide-angle (b) XRD patterns of MMS-x
(111), (220), (311), (400), (422), (511), and (440), of stan-
dard Fe O crystal with space group Fd3m structure (JCPDS
3
4
[
33]
7
5-1609).
The patterns also display that the intensities of
all diffraction peaks seem to increase with the increase in the
amount of Fe O , as was further confirmed by the magneti-
3
4
3 4
zation study below.
magnetic Fe O content of 13.6 , 20.2, 24.7, and 38.2 wt%
3 4
in MMS-x, respectively, by comparing the reference value
2
.1.3
|
N
2
adsorption–desorption measurement
[35]
for the pure Fe O (87.8 emu/g).
This further confirms
3
4
The nitrogen sorption isotherms of MMS with different mag-
netite amounts are shown in Figure 3. All the adsorption iso-
therms are typical type IV with type H1 hysteresis loops,
that the magnetization values are tunable in a certain range
by varying the added amount of Fe O . MMS-x with a high
3
4
magnetization value can quickly respond to the external
magnetic field and thus their immobilized BCL can be sepa-
rated from the reaction system readily by a magnet.
[34]
which are characteristic of the mesostructure.
As the
amount of Fe O nanoparticles embedded in the MMS is
3
4
increased, the sorption isotherms still remained the same
type. This implies that the existence of Fe O nanoparticles
3
4
TABLE 1 Textural properties and saturation magnetization of MMS-x
did not prevent the packing and self-assembly of the TEOS/
CTAB complex from forming an ordered mesoporous struc-
ture, which is in accordance with the XRD results. The nar-
row and sharp pore size distribution curves (inset of
Figure 3) show that the MMS-x has uniform-sized meso-
pores. Their structural parameters are summarized in
Table 1.
Pore
diameter
(nm)
Pore
Specific
Saturation
magnetization
(emu/g)
volume
surface area
3
2
Sample
(cm /g)
(m /g)
MMS-0.075
MMS-0.10
MMS-0.125
MMS-0.25
2.96
2.98
2.88
2.89
0.53
0.47
0.45
0.54
504
420
404
442
11.9
17.7
21.7
33.5

4
XUE ET AL.
[
16,25]
MMS-x facilitated the mass transfer.
These favorable
factors make MMS-x a very suitable carrier for lipase
immobilization.
For BCL/MMS-x, when x was no more than 0.10 g, they
showed superior catalytic ability. The C% reached the maxi-
mum theoretical value (50%) with 99% ee, which depends
on the properties of the used BCL for kinetically controlled
[
41]
synthesis.
However, increasing x continuously resulted in
a decrease in the catalytic activity. It is probable that exces-
sive Fe O4 provides more opportunities for interactions
3
between Fe O and BCL under the same BCL quality, and,
3
4
as a result, the access of the substrate alcohol molecules to
the active sites of BCL reduces. Besides the catalytic activ-
ity, the magnetism of BCL/MMS-x is also a factor that needs
to be considered because it determines the separation and
recovery of BCL/MMS-x. To take account of the above two
factors, BCL/MMS-0.10 was chosen for further
investigation.
FIGURE 4 Field-dependent magnetization curves at room temperature for
MMS-x
2.2 | Catalytic performance of BCL/MMS-x
2
.2.1
|
Effect of Fe
3
O
4
content on the resolution of
2.2.2 | Resolution of different racemic secondary alcohols
1
-phenylethanol
To widen the range of application, BCL/MMS-0.10 was also
employed in the resolution of two other aromatic substrates,
namely 1-phenyl-1-propanol (2) and 1-(4-bromophenyl) eth-
anol (3), under the identical conditions as 1-phenylethanol
(1). During the reaction, 100-μL samples were withdrawn at
different intervals of time and analyzed by gas chromatogra-
phy (GC) as described in Section 3.5. Figure 5 plots the pro-
In previous reports, Fe O was always embedded into meso-
porous silica as a magnetism source with the purpose of easy
separation and recovery for lipase, but whether it affected the
3
4
catalytic activity of lipase immobilized onto the Fe O /silica
3
4
composite materials has received little attention. In this study,
the effects of enzyme loading and textural properties of
MMS-x could be excluded because of the complete immobili-
zation in isooctane and the almost same pore size, pore vol-
ume, and surface area (Table 1). Under such circumstances,
more reliable and exact conclusion can be reached on the
effect of Fe O content on the catalytic activity of the MMS-x
for resolution of 1-phenylethanol to synthesize chiral alcohol
and the corresponding ester. From Table 2, all BCL/MMS-x
exhibited far higher activity than the non-immobilized BCL
in terms of the conversion of 1-phenylethanol (C%), and the
gress of ee with the time course catalyzed by the non-
S
immobilized BCL and BCL/MMS-0.10. It should be noted
that the ee values for the resolution of (1) (2), and (3) cata-
P
lyzed by the non-immobilized BCL or BCL/MMS-0.10
remained 99% invariant even after 48 hr of reaction time;
therefore, the data is not given. Moreover, according to the
formula in Section 3.5, estimation of the catalytic activity
3
4
utilizing ee
the average reaction rate for 6 hr under the BCL/MMS-0.10
is actually based on using C%. From Figure 5,
S
enantiomeric excess of (S)-1-phenylethanol (ee ), meanwhile,
S
achieved the same enantiomeric excess of (R)-1-phenylethyl
acetate (ee ), indicating a faster reaction rate. The result can
P
be explained by the following reasons: (a) non-immobilized
BCL got aggregated in the organic solvent, leading to low
[11,36]
dispersion and diffusion limitation;
(b) during the pro-
cess of immobilization, hydrophobic isooctane promotes the
interfacial activation of the BCL, thus improving its catalytic
[
37–40]
activity;
(c) the large number of mesopores of the
3 4
TABLE 2 Effect of Fe O content on the catalytic activity of the
BCL/MMS-x in the resolution of 1-phenylethanol for 6 hr
Catalyst
ee
S
(%)
ee
P
(%)
C (%)
10.9
50.0
50.0
44.4
45.0
E
BCL
12.1
99
99
99
99
99
99
224
1,057
1,057
483
502
BCL/MMS-0.075
BCL/MMS-0.10
BCL/MMS-0.125
BCL/MMS-0.25
99
FIGURE 5 Process curves of ee
-phenyl-1-propanol (2), and 1-(4-bromophenyl) ethanol (3) under non-
immobilized BCL and the BCL/MMS-0.10
S
for the resolution of 1-phenylethanol (1),
79.0
81.1
1

XUE ET AL.
5
was ~4.4–8 times higher than that under the non-
immobilized BCL, which is still ascribed to diffusion limita-
tion and interfacial activation. It is also observed that the
substitution on the benzene ring and the increase of carbon
chain bearing the chiral carbon atom lowered the reaction
China). CTAB, vinyl acetate, heptane, sodium acetate trihy-
drate, ferric chloride, ethylene glycol, and other reagents
were supplied by Sinopharm Chemical Reagent Beijing Co.,
Ltd. (Beijing, China).
[42]
rate
irrespective of whether non-immobilized BCL or
3
.2 | Preparation of magnetic mesoporous silica
BCL/MMS-0.10 was used, and the reaction rate followed
the same order of (1) > (3) > (2), which proved that the
immobilization of BCL on MMS-0.1 did not alter the cata-
lytic behavior of BCL such as substrate specificity or
enantioselectivity.
Fe O microspheres were prepared by the solvothermal
3
4
[
33]
method.
FeCl ꢁ6H O (15 mmol) was dissolved in ethyl-
3
2
ene glycol (75 mL) to form a clear solution; then 10.8 g
NaAc and 1.5 g polyethylene glycol 400 were added into the
above solution. The mixture was stirred vigorously for 1 h
and then sealed in a Teflon-lined stainless steel autoclave,
2
.2.3 | Repeated use of BCL/MMS-0.10
ꢀ
which was heated at 200 C for 24 hr and then cooled to
From an economic perspective, stability and recovery of the
lipase is the most important function of immobilization. As
shown in Figure 6, BCL/MMS-0.10 showed excellent opera-
tional stability in the resolution of 1-phenylethanol (1),
ambient temperature. The as-prepared black precipitate was
washed several times with deionized water and ethanol and
ꢀ
then dried at 70 C for 12 hr.
The above Fe O microspheres were added in 25 mL
3
4
1-phenyl-1-propanol (2), and 1-(4-bromophenyl) ethanol (3).
H O and followed by 0.83 g CTAB and 1 mL triethylamine
2
After five cycles, the activity of BCL/MMS-0.10 still
remained above 90% of the initial activity for all the resolu-
tion reaction, while a small quantity of the non-immobilized
BCL was nearly lost in the first cycle use and difficult to
recycle. It is also found that the activity for the second cycle
was even a little higher than the initial activity, which is
mainly due to the existence of the induction period in the
after ultrasonication for 15 min. After vigorous mechanical
stirring for 1 hr, TEOS was added and stirred for another
3
hr, and then the gray black emulsion was transferred into
ꢀ
thautoclave and crystallized at 100 C for 48 hr. The emulsion
was filtered, washed, and dried. Finally, the solid powder was
treated with refluxing acetone in order to remove surfactant
templates; the obtained products were designed as MMS-x,
where x denotes the added amount of Fe O (g) (Scheme 1).
[43]
reaction catalyzed by lipase.
The results indicate the
3
4
MMS-0.10 can improve the stability of BCL and provide a
convenient recovery.
3
.3 | Immobilization of BCL
Immobilization of BCL was conducted according to a proce-
3
3
| EXPERIMENTAL
.1 | Chemicals
[
44]
dure described previously,
in which BCL was completely
immobilized onto magnetic mesoporous silica (MMS-x) via
[37–40]
physical adsorption and interfacial activation.
First,
BCL was purchased from Amano (Shanghai, China).
0.1 g MMS-x was dispersed in 10 mL isooctane in a vessel,
1
1
-Phenylethanol,
-(4-bromophenyl) ethanol were from ACROS (Beijing,
1-phenyl-1-propanol,
and
and then 0.1 mL 0.1 M pH 6.5 phosphate buffer solution
[
11,45]
(PBS), which provided “essential water” and pH,
was
China); PEG400 was from Sigma Aldrich (Shanghai,
added to the above suspension. After stirring for a certain
time, 10 mg of BCL was dispersed into the suspension. Sub-
sequently, the vessel was placed in a shaking bath and
vibrated for 2 hr, and then the immobilized BCL was sepa-
rated from the medium by a magnet, dried in vacuum, and
ꢀ
stored at 4 C for later experiments. The resulting immobi-
lized BCL (9.09 wt.% of BCL) was denoted as
BCL/MMS-x.
3
.4 | Resolution of racemic secondary alcohols
A transesterification resolution of 1-phenylethanol with
vinyl acetate as activated acyl donor in an organic solvent is
FeCl3
HOCH CH OH
NaAc
o
200 C, 24 h
Extraction
of CTAB
TEOS
CTAB
2
2
solvothemal
FIGURE 6 Operation stability of BCL/MMS-0.10 in catalyzing resolution
of 1-phenylethanol (1), 1-phenyl-1-propanol (2), and 1-(4-bromophenyl)
ethanol (3)
Fe O
MMSP
3
4
SCHEME 1 Preparation of magnetic mesoporous silica (MMS-x)

6
XUE ET AL.
λ = 0.1540 nm (Rigaku D/MAX-2400, Japan); the surface
area, pore size distribution, and pore volume of the MMS-x
were determined by BET and BJH methods on a physisorp-
tion apparatus (ASAP-2010, USA). The magnetization
curves of MMS-x samples were recorded with a vibrating
sample magnetometer (VSM) at room temperature (Lake
Shore 7304, USA).
SCHEME 2 Transesterification resolution of 1-phenylethanol by
immobilized lipase
commonly utilized as a model reaction to evaluate the
[11,31]
enzyme activity/enantioselectivity,
as described in
Scheme 2. Specifically, 0.5 mmol racemic secondary alco-
hols and 1.0 mmol vinyl acetate were dissolved in 10 mL of
heptane followed by the addition of 100 mg of BCL/MMS-
x. The suspension was vibrated at 40 C for some time in a
water bath shake-bed. At the end of the process, the reaction
was terminated by simple magnetic separation.
4
| CONCLUSIONS
In this study, solvothermal and hydrothermal methods were
adopted for the successful synthesis of a series of MMS par-
ticles with large surface area and high saturation magnetiza-
tion. BCL immobilized on magnetic mesoporous silica
ꢀ
(
BCL/MMS) were obtained via simple physical adsorption
3
.5 | Activity evaluation of immobilized BCL
and interfacial activation in a hydrophobic organic solvent.
The as-prepared BCL/MMS composites showed good cata-
lytic behavior, including activity, enantioselectivity, and
reusability toward the kinetic resolution of aromatic second-
ary alcohols. It was indicated that the saturation magnetiza-
Activity of the BCL/MMS-x is expressed by the enantio-
meric excess of both substrate alcohol (ee ) and product
ester (ee ) as well as the total conversion of racemic sub-
strate alcohol (C, %). They were measured by a gas chro-
matograph (GC 2010, Shimadzu) equipped with a hydrogen
flame ionization detector (FID) and the chiral column CP-
Chirasil-Dex CB (25 m × 0.25 mm). Nitrogen was used as
the carrier gas with a pressure of 0.1 MPa. The temperatures
of injection, the column oven, and the detector were set at
2
and enantiomeric ratio (E) were calculated from the follow-
ing formulas according to the literature.
the non-immobilized BCL (the same mass as the BCL con-
tent in 100 mg of BCL/MMS-x) was also assessed under
identical reaction conditions as with BCL/MMS-x.
S
P
tion or the relative Fe O4 content embedded into the
3
mesoporous silica had a great influence on the catalytic per-
formance of BCL/MMS, as any further increase in the satu-
ration magnetization value (17.7 emu/g) led to a decrease in
the lipase-catalyzed reaction rate. The high magnetic suscep-
tibility facilitated fast recovery of the immobilized lipase
from reaction system and allowed its repeated use. The supe-
rior catalytic properties make the MMS-immobilized lipase
an attractive biocatalyst for the green synthesis of optically
active intermediates in a transesterification reaction system.
ꢀ
50, 108, and 250 C, respectively. The values of ee , ee , C
S
P
[46]
For comparison,
ACKNOWLEDGMENTS
½
Sꢂ −½Rꢂ
½Rꢂp −½Sꢂp
½Sꢂ þ½Rꢂ
s
s
eesð%Þ ¼
, eepð%Þ ¼
,
This work was supported by the National Natural Science
Foundation of China (21663020).
½
Sꢂ þ½Rꢂ
s
s
p
p
ln½1−Cð1þeepÞꢂ
ees
Cð%Þ ¼
, E ¼
:
eesþeep
ln 1−C 1−ee
½
ð
p
Þꢂ
REFERENCES
3
.6 | Operation stability of immobilized BCL
[
[
[
1] S. A. Costa, T. Tzanov, A. Paar, M. Gudelj, G. M. Gübitz, A. Cavaco-
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reaction was completed and washed with 3 mL heptane
before next text reaction under the same conditions. Accord-
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How to cite this article: Xue P, Hu C-M, Yan X-H,
Fang G-L, Shen H-F. Enhancement of activity and
reusability of lipase immobilized on magnetic meso-
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alcohols. J Chin Chem Soc. 2018;1–7. https://doi.org/
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