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Green Polymer Chemistry:
Biocatalysis and Biomaterials

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In Green Polymer Chemistry: Biocatalysis and Biomaterials; Cheng, H., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


ACS SYMPOSIUM SERIES 1043

Green Polymer Chemistry:
Biocatalysis and Biomaterials
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H. N. Cheng, Editor
Southern Regional Research Center
USDA - Agricultural Reseach Service

Richard A. Gross, Editor
Polytechnic Institute of New York University (NYU-POLY)

Sponsored by the
ACS Division of Polymer Chemistry

American Chemical Society, Washington, DC
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Library of Congress Cataloging-in-Publication Data
Green polymer chemistry : biocatalysis and biomaterials / H. N. Cheng, Richard A. Gross,
editors.
p. cm. -- (ACS symposium series ; 1043)
Includes bibliographical references and index.
ISBN 978-0-8412-2581-7 (alk. paper)
1. Biodegradable plastics--Congresses. 2. Environmental chemistry--Industrial
applications--Congresses. 3. Biopolymers--Congresses. I. Cheng, H. N. II. Gross, Richard
A., 1957TP1180.B55G74 2010
547’.7--dc22
2010023453

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Foreword
The ACS Symposium Series was first published in 1974 to provide a
mechanism for publishing symposia quickly in book form. The purpose of
the series is to publish timely, comprehensive books developed from the ACS
sponsored symposia based on current scientific research. Occasionally, books are
developed from symposia sponsored by other organizations when the topic is of
keen interest to the chemistry audience.
Before agreeing to publish a book, the proposed table of contents is reviewed

for appropriate and comprehensive coverage and for interest to the audience. Some
papers may be excluded to better focus the book; others may be added to provide
comprehensiveness. When appropriate, overview or introductory chapters are
added. Drafts of chapters are peer-reviewed prior to final acceptance or rejection,
and manuscripts are prepared in camera-ready format.
As a rule, only original research papers and original review papers are
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Preface
Green Polymer Chemistry is a crucial area of research and product
development that continues to grow in its influence over industrial practices.
Developments in these areas are driven by environmental concerns, interest in
sustainability, desire to decrease our dependence on petroleum, and commercial
opportunities to develop “green” products. Publications and patents in these fields
are increasing as more academic, industrial, and government scientists become
involved in research and commercial activities.
The purpose of this book is to publish new work from a cutting-edge group
of leading international researchers from academia, government, and industrial
institutions. Because of the multidisciplinary nature of Green Polymer Chemistry,
corresponding publications tend to be spread out over numerous journals. This

book brings these papers together so that the reader can gain a better appreciation
of the breadth and depth of activities in Green Polymer Chemistry.
This book is based on contributions by oral and poster presenters at the
international symposium, Biocatalysis in Polymer Science, held at the ACS
National Meeting in Washington D.C. on August 17-20, 2009. Whereas many
aspects of Green Polymer Chemistry were covered during the symposium, a
particular emphasis was placed on biocatalysis and biobased materials. Many
exciting new findings in basic research and applications were reported. In
addition, several leaders in these areas who were unable to attend the symposium
contributed important reviews of their ongoing work. As a result this book
provides a good representation of activities at the forefront of research in Green
Polymer Chemistry emphasizing activities in biocatalysis and biobased chemistry.
This book will be useful to scientists and engineers (chemists, biochemists,
chemical engineers, biochemical engineers, material scientists, microbiologists,
molecular biologists, and enzymologists) as well as graduate students who are
engaged in research and developments in polymer biocatalysis and biomaterials.
It can also be a useful reference book for those interested in these topics.
We thank the authors for their timely contributions and their cooperation while
the manuscripts were being reviewed and revised. In addition we also thank the
ACS Division of Polymer Chemistry, Inc. for sponsoring the 2009 symposium
and providing generous funding for the symposium.

xi
In Green Polymer Chemistry: Biocatalysis and Biomaterials; Cheng, H., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


H. N. Cheng

Southern Regional Research Center

USDA – Agricultural Research Service
1100 Robert E. Lee Blvd.
New Orleans, LA 70124

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Richard A. Gross

Herman F. Mark Professor
Director: NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules
Polytechnic Institute of NYU (NYU-POLY)
Six Metrotech Center
Brooklyn, NY 11201

xii
In Green Polymer Chemistry: Biocatalysis and Biomaterials; Cheng, H., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


Chapter 1

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Green Polymer Chemistry: Biocatalysis and
Biomaterials‡
H. N. Cheng1,* and Richard A. Gross2
1Southern


Regional Research Center, USDA/Agriculture Research Service,
1100 Robert E. Lee Blvd., New Orleans, LA 70124
2NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules,
Polytechnic Institute of NYU (NYU-POLY), Six Metrotech Center, Brooklyn,
NY 11201, />*
‡Names of products are necessary to report factually on available data;
however, the USDA neither guarantees nor warrants the standards of the
products, and the use of the name USDA implies no approval of the products
to the exclusion of others that may also be suitable.

This overview briefly surveys the practice of green chemistry in
polymer science. Eight related themes can be discerned from the
current research activities: 1) biocatalysis, 2) bio-based building
blocks and agricultural products, 3) degradable polymers,
4) recycling of polymer products and catalysts, 5) energy
generation or minimization during use, 6) optimal molecular
design and activity, 7) benign solvents, and 8) improved
synthesis to achieve atom economy, reaction efficiency, and
reduced toxicity. All of these areas are experiencing an increase
in research activity with the development of new tools and
technologies. Examples are given of recent developments in
green chemistry with a focus on biocatalysis and biobased
materials.

© 2010 American Chemical Society
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Introduction
Green chemistry is the design of chemical products and processes that reduce
or eliminate the use or generation of hazardous substances (1). Sustainability refers
to the development that meets the needs of the present without compromising the
ability of future generations to meet their own needs (2). In the past few years these
concepts have caught on and have become popular topics for research. Several
books and review articles have appeared in the past few years (3–6).
In the polymer area, there is also increasing interest in green chemistry. This is
evident by many recent symposia organized on this topic at national ACS meetings.
In our view, developments in green polymer chemistry can be roughly grouped into
the following eight related themes. These eight themes also agree well with most
of the themes described in recent articles and books on green chemistry (3–6).
1) Greener catalysts (e.g., biocatalysts such as enzymes and whole cells)
2) Diverse feedstock base (especially agricultural products and biobased
building blocks)
3) Degradable polymers and waste minimization
4) Recycling of polymer products and catalysts (e.g., biological recycling)
5) Energy generation or minimization of use
6) Optimal molecular design and activity
7) Benign solvents (e.g., water, ionic liquids, or reactions without solvents)
8) Improved syntheses and processes (e.g., atom economy, reaction
efficiency, toxicity reduction)
In this article, we provide an overview of green polymer chemistry, with
a particular emphasis on biocatalysis (7, 8) and biobased materials (9, 10).
Examples are taken from the recent literature, especially articles in this symposium
volume (11–39) and the preprints (40–62) from the international symposium on
“Biocatalysis in Polymer Science” at the ACS national meeting in Washington,
DC in August 2009.


Green Polymer Chemistry - The Eightfold Path
Biocatalysts
Biocatalysis is an up-and-coming field that has attracted the attention
and participation of many researchers. Several reviews (7) and books (8) are
available on biocatalysis. This current symposium volume documents important
new research that uses biocatalysis and biobased materials as tools to describe
practical and developing strategies to implement green chemistry practices.
A total of 22 articles (and 17 symposium preprints) describe biocatalysis and
biotransformations. Among these papers, 31 articles focus on cell-free enzyme
catalysts and 8 utilize whole-cell catalysts to accomplish biotransformations.

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Biobased Materials

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Interest in biobased materials (9, 10) appears to be increasing proportionally
with increases or increased volatility of crude oil prices. There is also general
recognition that the resources of the world are limited, and sustainability has
become a rallying point for many organizations and industries participating in
chemical product development. Thus, there is growing interest in using readily
renewable materials as ingredients for commercial products or raw materials for
synthesis and polymerization. In this book, 14 articles deal with biobased raw
materials or products. In addition, 11 symposium preprints focus on this topic.


Degradable Polymers and Waste Minimization
One advantage of agricultural raw materials and bio-based building blocks
is that they are potentially biodegradable and have less negative environmental
impact. In addition to the potential economic benefits, the use of agricultural
by-products minimizes waste and mitigates disposal problems. Biocatalysis
is helpful in this effort because enzyme-catalysts often catalyzed reactions of
natural substrates at high rates. Many biobased products are biodegradable, and
hydrolytic enzymes are critically important for the break down of biomass to
usable building blocks for fermentation processes. Four of the articles in this
book deal specifically with polymer degradation and hydrolysis (20, 34–36). In
addition, most of the polymers described in this book (polyesters, polyamides,
polypeptides, polysaccharides) are biodegradable or potentially biodegradable.

Recycling
Another advantage of agricultural raw materials and bio-based building
blocks is that they can often be recycled. Some resulting polymers that are
biodegradable can undergo biological recycling by which they are converted to
biomass, CO2, CH4 (anaerobic conditions) and water. Recycling is also important
for biocatalysts in order to decrease process cost; this is one of the reasons for the
use of immobilized enzymes. Several examples of immobilized enzymes appear
in this book (vide infra). A popular enzyme used thus far is Novozym® 435 lipase
from Novozymes A/S, which is an immobilized lipase from Candida antarctica.

Energy Generation and Minimization of Use
An active area of research is biofuels, and many review articles are available
(63, 64). First generation products have largely been based on biotransformation
of sugars and starch. The second-generation products, based on lignocelluloses
conversion to sugars, are still under development. Biocatalysis is compatible
with energy savings because their use often involves lower reaction temperatures

and, therefore, lower energy input (e.g., refs. (27, 48)). The reactive extrusion
technique is another process methodology that can decrease energy use (38, 39).
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Molecular Design and Activity

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In polymer science, structure-property and structure-activity correlations are
often employed as part of synthetic design, and many articles on synthesis in
this book inherently incorporated this feature. In biochemistry, a good example
of molecular design is the development via protein engineering of protein
variants that are optimized for a particular activity or characteristic (e.g. thermal
stability). For example, Kiick (40) used in vivo methods to produce resilin, and
McChalicher and Srienc (50) used site-specific mutagenesis for the synthase
that produces poly(hydroxyalkanoate)s. In a different way, Ito et al (18) used
molecular recognition to optimize biological activity of aptamers. Li et al (29)
used biopathway engineering to produce lipopolysaccharides and their analogs.

Benign Solvents
A highly desirable goal of green chemistry is to replace organic solvents in
chemical reactions with water. Biocatalytic reactions are highly suited for this. In
fact, all whole-cell biotransformations and many enzymatic reactions in this book
are performed in aqueous media. An alternative is to carry out the reaction without
any solvents, as exemplified by several articles in this book.


Improved Syntheses and Processes
Optimization of experimental parameters in synthesis and process
improvement during scale-up and commercialization are part of the work that
synthetic scientists and engineers do. Biocatalysis certainly brings a new
dimension to reactions and processes. Biocatalytic reactions often involve fewer
by-products and less (or no) toxic chemical reagents. Several new or improved
synthetic and process methodologies are described in the following sections. In
addition, it is noteworthy that Matos et al (52) used microwave energy to assist
in lipase-catalyzed polymerization, and Fishman et al (15) used microwave for
extraction. Wang et al (38, 39) used reactive extrusion to facilitate polymer
modification reactions.
From the foregoing discussion, it is clear that biocatalysis and biobased
materials are major contributors to current research and development activities in
green polymer chemistry. Active researchers in these fields have been working
with different polymers, different biocatalysts, and different strategies. For
convenience, the rest of this review is divided into eight sections: 1) Novel
Biobased Materials, 2) New or Improved Biocatalysts, 3) Synthesis of Polyesters
and Polycarbonates, 4) Synthesis of Polyamides and Polypeptides, 5) Synthesis
and Modification of Polysaccharides, 6) Biocatalytic Redox Polymerizations, 7)
Enzymatic Hydrolysis and Degradation, and 8) Grafting and Functionalization
Reactions.

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ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


Novel Biobased Materials
As noted earlier, biobased materials constitute one of the most active
research areas today. These include polypeptides/proteins, carbohydrates,

lipids/triglycerides, microbial polyesters, plant fibers, and many others.

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Polypeptides/Proteins
An active area of research is to use polypeptides and proteins for various
applications. Kiick (40) worked with resilin, the insect energy storage protein
that shows useful mechanical properties. This work involved incorporation of
unnatural amino acids to produce biomaterials for possible use in engineering
the vocal folds (more commonly known as vocal cords). Liu et al (12) carried
out biofabrication based on enzyme-catalyzed coupling and crosslinking of
pre-formed biopolymers for potential use as medical adhesives. Renggli and Bruns
(11) reviewed polymer-protein hybrid materials and their use as biomaterials
and biocatalytic polymers. Zhang and Chen (13) made novel blends of soy
proteins and biodegradable thermoplastics, which exhibit excellent mechanical
properties. Jong (57) made composites from rubber and soy protein modified
with phthalic anhydride and found they provide a significant reinforcement effect.
Venkateshan and Sun (14) made urea-soy protein composites and characterized
their thermodynamic behavior and structural changes.
Polysaccharides
DeAngelis (30) and Schwach-Abdellaoui et al (31) both worked with
glycoaminoglycans, which are useful in drug delivery, implantable gels, and cell
scaffolds. Li et al (29) carried out extensive work in in vitro biosynthesis of
O-polysaccharides and in vivo production of liposaccharides. Bulone et al (48)
described a low-energy biosynthetic approach for the production of high-strength
nanopaper from compartmentalized bacterial cellulose fibers. Fishman et al (15)
extracted polysaccharides from sugar beet pulp and extensively characterized the
resulting fractions.
Lipids and Triglycerides

In their article, Lu and Larock (16) provided a good overview of their work
on converting agricultural oils into plastics, rubbers, composites, coatings and
adhesives. Zini, et al (41) reviewed their work on poly(sophorolipid) and its
potential as a biomaterial. Lu, et al (44) produced new ω-hydroxy and ω-carboxy
fatty acids as building blocks for functional polyesters.
Specialty Polymeric Materials
Dinu et al (17) made smart coatings by immobilizing enzymes on carbon
nanotubes and incorporating them into latex paints. The resulting materials can
detect and eliminate hazardous agents to combat chemical and biological agents.
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In Green Polymer Chemistry: Biocatalysis and Biomaterials; Cheng, H., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


Xue, at al (61) made poly(ester-urethanes) based on poly(ε-caprolactone) that
exhibit shape-memory effect at body temperature. Rovira-Truitt and White (43)
prepared poly(D,L-lactide)/tin-supported mesoporous nanocomposites by in-situ
polymerization.

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Biomaterials
Most of the above aforementioned materials can be used in medical and
dental applications as biomaterials, e.g., tissue engineering, implants, molecular
imprinting, stimuli responsive systems for drug delivery and biosensing.
Moreover, the nucleic acid-based aptamer described by Ito et al (18) has potential
use for biosensing, diagnostic, and therapeutics. In addition, most of the
polyesters described in this book are biodegradable and also have potential use
in medical applications. For example, polylactides and polyglycolides are well

known bioresorbable polyesters used as sutures, stents, dialysis media, drug
delivery devices and others.

New and Improved Biocatalysts
Not surprisingly, one of the active research areas of biocatalysis and
biotransformation is the development of new and improved biocatalysts.
New or Improved Enzymes
Methods to improve protein activity, specificity, stability and other
characteristics are rapidly developing both through high-throughput as well
as information-rich small library strategies.
An example was given by
McChalicher and Srienc (50) who modified the synthase to facilitate the synthesis
of poly(hydroxyalkanoate) (PHA). Ito et al (18) described a different class
of enzymes (“aptazymes”) based on oligonucleotides, which bind to hemin
(iron-containing porphyrin) and also show peroxidase activity.
Ganesh and Gross (34) embedded enzymes within a bioresorbable
polymer matrix, thereby demonstrating a new concept by which the lifetime
of existing bioresorbable materials can be “fine tuned.” Gitsov et al (45) made
enzyme-polymer complexes that form “nanosponges.” Renggli and Bruns (11)
also made enzyme-polymer hybrid materials. Schoffelen et al (19, 46) developed
a method to introduce an azide group onto an enzyme, which allowed subsequent
coupling via click chemistry to other structures such as a polymer or enzyme(s)
to facilitate reactions that require multiple enzymes. Immobilized enzymes were
also used by a large number of authors in this book.
Whole Cell Approaches
Whole cell approaches were used by Yu (21) and by Smith (47) to produce
PHA. Li et al (29) conducted in vitro biosynthesis of O-polysaccharides and
in vivo production of liposaccharides. Schwach-Abdellaoui et al (31) used
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In Green Polymer Chemistry: Biocatalysis and Biomaterials; Cheng, H., et al.;

ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


a transferred gene in Bacillus subtilis to produce hyaluronic acid through an
advanced fermentation process. Bulone et al (48) produced cellulose nanofibrils
via Gluconacetobacter xylinus in the presence of hydroethylcellulose. Lu
et al (44) produced ω-hydroxy and ω-carboxy fatty acids by engineering a
Candida tropicalis strain and the corresponding fermentation processes. Uses
of ω-hydroxy and ω-carboxy fatty as biobased monomers for next-generation
poly(hydroxyanoates) was discussed.
In their review on Baeyer-Villiger
biooxidation Lau et al (33) included whole cell approaches. In her article, Kawai
(36) summarized microorganisms capable of degrading polylactic acid.

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Syntheses of Polyesters and Polycarbonates
Many examples of biocatalytic routes to polyesters and polycarbonates
are discussed in this book and corresponding symposium preprints. In order
to facilitate accessing these contributions to the book, the specific polymers,
biocatalysts and authors for each polymer system are summarized in the following
Table 1.

Syntheses of Polyamides and Polypeptides
Resilin-like polypeptides were made via whole cell biocatalysis described by
Kiick (40). Co-oligopeptides consisting of glutamate and leucine residues were
prepared via protease catalysis by Li et al (42). Polyamides were synthesized via
lipase catalysis by Gu et al (49), by Cheng and Gu (27), and by Loos et al (53).
Palmans et al (53) used dynamic kinetic resolution method to form chiral esters

and amides, which can potentially lead to chiral polyamides.

Syntheses and Modifications of Polysaccharides
As noted earlier, DeAngelis (30) and Schwach-Abdellaoui et al (31)
both produced glycoaminoglycans through cell-free enzyme and whole-cell
approaches, respectively, and Bulone et al (48) produced bacterial cellulose
through a whole-cell approach. Li et al (29) produced O-polysaccharides and
liposaccharides through in vitro and in vivo biosynthesis. Fishman et al (15)
made carboxymethylcellulose with materials obtained from sugar beet pulp. In
addition, Biswas et al (56) grafted polyacrylamide onto starch using horseradish
peroxidase as a catalyst.

Biocatalytic Redox Polymerizations
In their chapter, Bouldin et al (32) provided a good review of the use
of oxidoreductase as a catalyst for the synthesis of electrically conducting
polymers based on aniline, pyrrole, and thiophene. In a preprint (58), they
reported a low-temperature, template-assisted polymerization of pyrrole
using soybean oxidase in an aqueous solvent system. In another study,
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Table 1. Examples of polyester and polycarbonate synthesis via biocatalysis
Polymera

Biocatalystb


Authors

Ref.

PHA

Whole cell

Yu

(21)

PHA

Whole cell with
mutant enzyme

McChalicher, Srienc

(50)

PHA (Mirel™)

Whole cell

Smith

(47)


Functional polycarbonates

Lipase (N-435)

Bisht, Al-Azemi

(22)

Copolymers of
PDL, caprolactone,
valerolactone, dioxanone,
trimethylenecarbonate

Lipase (N-435)

Scandola et al

(23)

Poly(PDL-co-glycolate)

Lipase (N-435)

Jiang, Liu

(24)

Polycaprolactone

Embedded N-435


Ganesh, Gross

(34)

Polyol polyesters

Lipase (N-435)

Gross, Sharma

(51)

Polycaprolactone

Lipase (N-435)

Matos et al

(52)

Chiral polyesters

Lipase (N-435)

Palmans et al

(53)

Poly(carbonate-co-ester),

terpolymer

Lipase (N-435)

Jiang et al

(54)

Poly(carbonate-co-ester),
diblock

Lipase (N-435)

Dai et al

(55)

Poly(PDL-co-butylene-cosuccinate)

Lipase (N-435)

Mazzocchetti et al

(60)

Polycaprolactone-based
poly(ester-urethanes)

Lipase (N-435)


Xue et al

(61)

Polycaprolactone diol

Immobilized lipase
from Y. lipolytica

Barrera-Rivera et al

(25)

Polyester elastomer from
12-hydroxystearate, itaconate,
and 1,4-butanediol

Immobilized lipase
from B. cepacia

Yasuda et al

(26)

Polyesters

(Immobilized)
Cutinase

Baker, Montclare


(20)

a PHA = poly(hydroxyalkanoate), PDL = ω-pentadecalactone,
435

b

N-435 = Novozym®

Cruz-Silva et al (59) polymerized pyrrole using horseradish peroxidase/H2O2 and
2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) as mediator.
Lau et al (33) provided a useful review on Baeyer-Villiger biooxidative
transformations, covering both cell-free enzyme and whole-cell approaches. Liu
et al (12) used a tyranosinase to conjugate pre-formed biopolymers.

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Enzymatic Hydrolyses and Degradation
Ganesh and Gross (34) demonstrated the concept of controlled biomaterial
lifetime by embedded Novozym® 435 lipase into poly(ε-caprolactone). By
using different quantities of embedded enzyme in films, they controlled the
degradation rate and tuned the lifetime of these biomaterials. Ronkvist et
al (35) discovered surprisingly rapid enzymatic hydrolysis of poly(ethylene

terephthalate) using cutinases. The ability of cutinases to carry out polymer
hydrolysis and degradation was also noted by Baker and Montclare (20) in their
review on cutinase. A good review was provided by Kawai (36) on poly(lactic
acid)-degrading microorganisms and depolymerases. Some proteases were
found to be specific to poly(L-lactic acid), but lipases active for poly(lactic acid)
hydrolysis preferred degrading poly(D-lactic acid).

Grafting and Functionalization Reactions
Puskas and Sen (37) used the immobilized lipase-catalyst system
Novozym 435 to catalyze methacrylation of hydroxyl functionalized
polyisobutylene and polydimethylsiloxane as well as conjugation of thymine
onto poly(ethylene glycol). Wang and Schertz (39) grafted poly(lactic acid)
onto poly(hydroxyalkanoate) using a reactive extrusion process. Wang and He
(38) modified poly(lactic acid) and poly(butylene succinate) with a diol or a
functionalized alcohol via a catalyst, also using a reactive extrusion process.
Moreover, as noted earlier, polyacrylamide was grafted onto starch using
horseradish peroxidase by Biswas et al (56).

References
1.
2.
3.
4.
5.
6.
7.

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Stevens, F. S. Green Plastics: An Introduction to the New Science of
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Chemistry: Cambridge, U.K., 2002.
Matlack, A. S. Introduction to Green Chemistry; Marcel Dekker: New York,
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(c) Biocatalysis in Polymer Science; Gross, R. A.; Cheng, H. N., Eds.;
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Series 1043 (this volume); American Chemical Society: Washington, DC,
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Liu, Y.; Yang, X.; Shi, X.; Bentley, W. E.; Payne, G. F. Biofabrication
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Biopolymers. Green Polymer Chemistry: Biocatalysis and Biomaterials;

ACS Symposium Series 1043 (this volume); American Chemical Society:
Washington, DC, 2010; Chapter 3.
Zhang, J.; Chen, F. Development of Novel Soy Protein-Based Polymer
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Fishman, M. L.; Cooke, P. H.; Hotchkiss, A. T., Jr. Extraction and
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American Chemical Society: Washington, DC, 2010; Chapter 6.
Lu, Y.; Larock, R. C. Novel Biobased Plastics, Rubbers, Composites,
Coatings and Adhesives from Agricultural Oils and By-Products. Green
Polymer Chemistry: Biocatalysis and Biomaterials; ACS Symposium Series
1043 (this volume); American Chemical Society: Washington, DC, 2010;
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Dinu, C. Z.; Borkar, I. V.; Bale, S. S.; Zhu, G.; Sanford, K.; Whited, G.;
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Antifouling, Chemical and Biological Decontamination. Green Polymer
Chemistry: Biocatalysis and Biomaterials; ACS Symposium Series 1043
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Liu, M.; Abe, H.; Ito, Y. Hemin-Binding Aptamers and Aptazymes. Green
Polymer Chemistry: Biocatalysis and Biomaterials; ACS Symposium Series
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19. Schoffelen, S.; Schobers, L.; Venselaar, H.; Vriend, G.; van Hest, C. C. M.
Synthesis of Covalently Linked Enzyme Dimers. Green Polymer Chemistry:
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20. Baker, P. J.; Montclare, J. K. Biotransformations Using Cutinase. Green
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Chapter 11.
21. Yu, J. Biosynthesis of Polyhydroxyalkanoates from 4-Ketovaleric Acid in
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22. Bisht, K. S.; Al-Azemi, T. F. Synthesis of Functional Polycarbonates
from Renewable Resources. Green Polymer Chemistry: Biocatalysis
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23. Scandola, M.; Focarete, M. L.; Gross, R. A. Polymers from Biocatalysis:
Materials with a Broad Spectrum of Physical Properties. Green Polymer
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24. Jiang, Z.; Liu, J. Lipase-Catalyzed Copolymerization of ω-Pentadecalactone
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Chemistry: Biocatalysis and Biomaterials; ACS Symposium Series 1043
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25. Barrera-Rivera, K. A.; Marcos-Fernández, A.; Martínez-Richa, A. ChemoEnzymatic Syntheses of Polyester-Erethanes. Green Polymer Chemistry:
Biocatalysis and Biomaterials; ACS Symposium Series 1043 (this volume);
American Chemical Society: Washington, DC, 2010; Chapter 16.
26. Yasuda, M.; Ebata, H.; Matsumura, S. Enzymatic Synthesis and Properties of
Novel Biobased Elastomers Consisting of 12-Hydroxystearate, Itaconate and
Butane-1,4-diol. Green Polymer Chemistry: Biocatalysis and Biomaterials;
ACS Symposium Series 1043 (this volume); American Chemical Society:
Washington, DC, 2010; Chapter 17.
27. Cheng, H. N.; Gu, Q. Synthesis of Poly(aminoamides) via Enzymatic Means.
Green Polymer Chemistry: Biocatalysis and Biomaterials; ACS Symposium
Series 1043 (this volume); American Chemical Society: Washington, DC,
2010; Chapter 18.
28. Schwab, L. W.; Baum, I.; Fels, G.; Loos, K. Mechanistic Insight in the
Enzymatic Ring-Opening Polymerization of β-Propiolactam. Green Polymer
Chemistry: Biocatalysis and Biomaterials; ACS Symposium Series 1043
(this volume); American Chemical Society: Washington, DC, 2010; Chapter
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29. Li, L.; Yi, W.; Chen, W.; Woodward, R.; Liu, X.; Wang, P. G. Production of
Natural Polysaccharides and Their Analogues via Biopathway Engineering.
Green Polymer Chemistry: Biocatalysis and Biomaterials; ACS Symposium
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DeAngelis, P. L. Glycosaminoglycan Synthases: Catalysts for Customizing
Sugar Polymer Size and Chemistry. Green Polymer Chemistry: Biocatalysis
and Biomaterials; ACS Symposium Series 1043 (this volume); American
Chemical Society: Washington, DC, 2010; Chapter 21.
Schwach-Abdellaoui, K.; Fuhlendorff, B. L.; Longin, F.; Lichtenberg, J.
Development and Applications of a Novel, First-in-Class Hyaluronic Acid
from Bacillus. Green Polymer Chemistry: Biocatalysis and Biomaterials;

ACS Symposium Series 1043 (this volume); American Chemical Society:
Washington, DC, 2010; Chapter 22.
Bouldin, R.; Kokil, A.; Ravichandran, S.; Nagarajan, S.; Kumar, J.;
Samuelson, L. A.; Bruno, F. F.; Nagarajan, R. Enzymatic Synthesis of
Electrically Conducting Polymers. Green Polymer Chemistry: Biocatalysis
and Biomaterials; ACS Symposium Series 1043 (this volume); American
Chemical Society: Washington, DC, 2010; Chapter 23.
Lau, P. C. K.; Leisch, H.; Yachnin, B. J.; Mirza, I. A.; Berghuis, A. M.; Iwaki,
H.; Hasegawa, Y. Sustained Development in Baeyer-Villiger Biooxidation
Technology. Green Polymer Chemistry: Biocatalysis and Biomaterials;
ACS Symposium Series 1043 (this volume); American Chemical Society:
Washington, DC, 2010; Chapter 24.
Ganesh, M.; Gross, R. A. Embedding Enzymes to Control Biomaterial
Lifetime. Green Polymer Chemistry: Biocatalysis and Biomaterials;
ACS Symposium Series 1043 (this volume); American Chemical Society:
Washington, DC, 2010; Chapter 25.
Ronkvist, Å. M.; Xie, W.; Lu, W.; Gross, R. A. Surprisingly Rapid
Enzymatic Hydrolysis of Poly(ethylene terephthalate). Green Polymer
Chemistry: Biocatalysis and Biomaterials; ACS Symposium Series 1043
(this volume); American Chemical Society: Washington, DC, 2010; Chapter
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Kawai, F. Polylactic Acid (PLA)-Degrading Microorganisms and PLA
Depolymerases. Green Polymer Chemistry: Biocatalysis and Biomaterials;
ACS Symposium Series 1043 (this volume); American Chemical Society:
Washington, DC, 2010; Chapter 27.
Puskas, J. E.; Sen, M. Y. Green Polymer Chemistry: Enzymatic
Functionalization of Liquid Polymers in Bulk. Green Polymer Chemistry:
Biocatalysis and Biomaterials; ACS Symposium Series 1043 (this volume);
American Chemical Society: Washington, DC, 2010; Chapter 28.
Wang, J. H.; He, A. Bio-Based and Biodegradable Aliphatic Polyesters

Modified by a Continuous Alcoholysis Reaction. Green Polymer Chemistry:
Biocatalysis and Biomaterials; ACS Symposium Series 1043 (this volume);
American Chemical Society: Washington, DC, 2010; Chapter 29.
Wang, J. H.; Schertz, D. M. Synthesis of Grafted Polylactic Acid and
Polyhydroxyalkanoate by a Green Reactive Extrusion Process. Green
Polymer Chemistry: Biocatalysis and Biomaterials; ACS Symposium Series
1043 (this volume); American Chemical Society: Washington, DC, 2010;
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40. Kiick, K. Modular biomolecular materials for engineering mechanically
active tissues. ACS Polym. Prepr. 2009, 50 (2), 53.
41. Zini, E.; Gazzano, M.; Scandola, M.; Gross, R. A. Glycolipid biomaterials:
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42. Li, G.; Viswanathan, K.; Xie, W.; Gross, R.A. Protease-catalyzed synthesis of
co-oligopeptides consisting of glutamate and leucine residues. ACS Polym.
Prepr. 2009, 50 (2), 60.
43. Rovira-Truitt, R.; White, J. L. Growing organic-inorganic biopolymer
nanocomposites from the inside out. ACS Polym. Prepr. 2009, 50 (2), 36.
44. Lu, W.; Yang, Y.; Zhang, X.; Xie, W.; Cai, M.; Gross, R. A. Fatty acid
biotransformations: omega-hydroxy- and omega-carboxy fatty acid building
blocks using a engineered yeast biocatalyst. ACS Polym. Prepr. 2009, 50
(2), 29.

45. Gitsov, I.; Simonyan, A.; Tanenbaum, S. Hybrid enzymatic catalysts for
environmentally benign biotransformations and polymerizations. ACS
Polym. Prepr. 2009, 50 (2), 40.
46. Schoffelen, S.; van Dongen, S. F. M.; Teeuwen, R.; van Hest, J. C. M. Azidefunctionalized Candida Antarctica lipase B for conjugation to polymer-like
materials. ACS Polym. Prepr. 2009, 50 (2), 3.
47. Smith, P. B. Renewable chemistry at ADM: Materials for the 21st century.
ACS Polym. Prepr. 2009, 50 (2), 62.
48. Zhou, Q.; Malm, E.; Nilsson, H.; Larsson, P. T.; Iversen, T.; Berglund, L. A.;
Bulone, V. Biomimetic design of cellulose-based nanostructured composites
using bacterial cultures. ACS Polym. Prepr. 2009, 50 (2), 7.
49. Gu, Q.; Michel, A.; Maslanka, W. W.; Staib, R.; Cheng, H. N. New polyamide
structures based on methyl acrylate and diamine. ACS Polym. Prepr. 2009,
50 (2), 54.
50. McChalicher, C.; Srienc, F. Synthesis of mixed class polyhydroxyalkanoates
using a mutated synthase enzyme. ACS Polym. Prepr. 2009, 50 (2), 67.
51. Gross, R.A.; Sharma, B. Lipase-catalyzed routes to polyol-polyesters. ACS
Polym. Prepr. 2009, 50 (2), 48.
52. Matos, T. D.; King, N.; Simmons, L.; Walker, C.; McClain, A.;
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optimize microwave assisted lipase catalyzed polymerizations. ACS Polym.
Prepr. 2009, 50 (2), 52.
53. Palmans, A. R. A.; Veld, M.; Deshpande, S.; Meijer, E. W. Candida
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ACS Polym. Prepr. 2009, 50 (2), 11.
54. Jiang, Z.; Liu, C.; Gross, R. A. Lipase-catalysis provides an attractive route
for poly(carbonate-co-esters) synthesis. ACS Polym. Prepr. 2009, 50 (2), 46.
55. Dai, S.; Xue, L.; Li, Z. Enzymatic preparation and characterization of
di-block co-polyester-carbonates consisting of poly[(R)-3-hydroxybutyrate]
and poly(trimethylene carbonate) blocks via ring-opening polymerization.
ACS Polym. Prepr. 2009, 50 (2), 21.

56. Shogren, R. L.; Willett, J. L.; Biswas, A. HRP-mediated synthesis of starchpolyacrylamide graft copolymers. ACS Polym. Prepr. 2009, 50 (2), 38.
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57. Jong, L. Effect of phthalic anhydride modified soy protein on viscoelastic
properties of polymer composites. ACS Polym. Prepr. 2009, 50 (2), 15.
58. Bouldin, R.; Ravichandran, S.; Garhwal, R.; Nagarajan, S.; Kumar, J.;
Bruno, F.; Samuelson, L.; Nagarajan, R. Enzymatically synthesized
water-soluble polypyrrole. ACS Polym. Prepr. 2009, 50 (2), 23.
59. Cruz-Silva, R.; Roman, P.; Escamilla, A.; Romero-Garcia, J. Enzymatic and
biocatalytic synthesis of polyaniline and polypyrrole colloids. ACS Polym.
Prepr. 2009, 50 (2), 475.
60. Mazzocchetti, L.; Scandola, M.; Jiang, Z. Enzymatic synthesis and thermal
properties of poly(omega-pentadecalactone-co-butylene-co-succinate). ACS
Polym. Prepr. 2009, 50 (2), 477.
61. Xue, L.; Dai, S.; Li, Z. Synthesis and characterization of three-arm
poly(epsilon-caprolactone)-based poly(ester–urethanes) with shape-memory
effect at body temperature. ACS Polym. Prepr. 2009, 50 (2), 579.
62. ACS Polymer Preprints can be accessed at />11.html?sm=87279.
63. Books on biofuels include (a) Handbook on Bioethanol: Production and
Utilization; Wyman, C. E., Ed.; Taylor and Francis: Washington, DC, 1996.
(b) Mousdale, D. M. Biofuels: Biotechnology, Chemistry and Sustainable
Development; CRC Press, New York, 2008. (c) Demirbas, A. Biofuels:
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(b) von Blottnitz, H.; Curran, M. A. J. Cleaner Prod. 2007, 15 (7), 607. (c)
Gomez, L. D.; Steele-King, C. G.; McQueen-Mason, S. J. New Phytol. 2008,
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Environmental, Economic and Policy Aspect of Biofuels; The World Bank
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14
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ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


Chapter 2

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Solid or Swollen Polymer-Protein Hybrid
Materials
Kasper Renggli and Nico Bruns*
Department of Chemistry, University of Basel, Klingelbergstr. 80, CH-4056
Basel, Switzerland
*Fax: +41 61 2673855; e-mail:

Hybrid materials comprising synthetic polymers and proteins
or active enzymes combine the best of two worlds: The
structural properties, the processibility and the moldability of
man-made plastics or gels and the highly evolved functionality
and responsiveness of nature’s polypeptides. In this chapter we
review the body of literature on these smart hybrid materials

and classify them according to their function. Biocatalytic
plastics and polymers, stimuli-responsive hybrid hydrogels,
self-assembled hydrogels with protein crosslinks, hybrid
materials for selective binding of heavy metal ions, materials
for tissue engineering, materials for controlled drug release,
biodegradable materials, smart hydrogels with improved
mechanical properties, and self-reporting materials are covered.

Introduction
Over the last century, we have witnessed an amazing rise of man-made
polymeric materials, which by now have made their way into nearly every
realm of our life. The reasons why polymeric materials found so widespread
applications (e.g., as structural components in every-day applications, as
construction materials, and as biomedical materials) and in many cases replaced
natural materials are that polymers are cheap and easy to manufacture, they are
easy to process and to mold into any desired shape. Furthermore, their properties
can be superior to their natural counterparts and the properties can be tailored to
fulfill specific needs by, e.g., the design of the chemical structure of the polymer.
More recently, polymers that respond to an external stimulus with a change in
© 2010 American Chemical Society
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their properties, so called smart materials, have attracted much attention (1–4).
Their potential application ranges from drug-delivery devices, to actuators,
sensors and microfluidic valves. Although a lot of polymer systems have been

labeled as smart, their responsiveness is most often limited to a single, quite
simple stimulus such as a change in temperature, a change in pH, or an increase
in ion concentration.
When it comes to multifunctional and smart materials, nature leads the way
with a number of responsive and adaptive materials (5). Form a few building
blocks, e.g., lipids, proteins, DNA, and carbohydrates, a variety of mesoscopic
materials are formed, such as cell membranes and cell walls, scaffold structures,
skin, plant leaves, etc. These materials are time-dependant, adaptive, responsive
and multifunctional. They can provide structural and mechanical stability, the
ability to integrate tissue, to regenerate and to grow. Moreover, they can process
information and sense optical, chemical and magnetic stimuli.
Hybrid materials that comprise biomolecules and man-made polymers can
be a means to combine the best of two worlds in one single material: The highly
evolved functionality and responsiveness of nature’s building blocks and the
structural properties, the processibility and moldability of synthetic polymers.
Although these hybrid materials do not reach the degree of functionality of some
natural materials yet, they offer a significant increase in functionality of smart
polymers.
This review will summarize the emerging field of polymer-protein hybrid
materials in the solid or the swollen state with a special focus on materials that
contain dispersed proteins in the polymer matrix. The various hybrid materials
reported in literature will be classified according to their function: Biocatalytic
plastics and polymers, stimuli-responsive hybrid hydrogels, self-assembled
hydrogels with protein crosslinks, hybrid materials for selective removal of heavy
metal ions from water, materials for tissue engineering, materials for controlled
drug release, biodegradable materials, smart hydrogels with improved mechanical
properties, and self-reporting materials.
Polymer-protein hybrid materials that are soluble in water (e.g.,
protein-polymer conjugates) (6, 7), or form colloidal nanostructures such as
protein-containing block copolymer vesicles (8, 9) have been extensively

reviewed elsewhere and are beyond the scope of this book chapter. The same
applies for peptide-polymer block copolymers and other peptide-polymer hybrid
structures (7, 10–13).

Polymer-Protein Hybrid Materials
Biocatalytic Plastics and Polymers
The immobilization of enzymes in or onto polymeric supports has long
been used as a means to improve the properties of the biocatalysts and might
be the earliest form of preparing polymer-protein hybrid materials (14). The
methods available to incorporate enzymes into polymeric supports include
entrapment, covalent attachment as well as adsorption and have been reviewed
extensively (15–17). Most often in the realm of biocatalysis, immobilized
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enzymes on or in polymeric supports were not regarded as hybrid materials
because the focus laid on the biocatalyst itself and the enhancement of its
properties due to the immobilization, e.g., by improving its catalytic properties
in water and non-aqueous media, by improving its stability and by allowing
for an easy recovery of the biocatalyst at the end of the reaction. On the other
hand, solid, powdered enzymes were blended into epoxy and other resins to
produce protein-aggregate-filled composites, e.g., for biosensor applications
(15). However, starting in the mid 1990s, biocatalytic materials began to emerge
that incorporated dispersed enzymes, i.e., starting with enzymes that were
soluble in the polymerization mixture (15, 18–20). Dordick and coworkers

drew the attention to the materials side of these systems and coined the term
biocatalytic plastics (20). Prior, Russell and coworkers had modified subtilisin
Carlsberg and thermolysin with pendant poly(ethyleneglycol) (PEG) acrylates
to yield organo-soluble, copolymerizable enzymes. They were copolymerized
by free radical polymerization with methyl methacrylate in the presence of
the crosslinker trimethylol propane trimethacrylate to yield hybrid materials
that retained high activities in aqueous, aqueous-organic and organic media
with improved long-term operational stabilites (18, 19). In their original work
on biocatalytic plastics, Dordick and coworkers modified α-chymotrypsin and
subtilisin Carlsberg with acryloyl chloride in order to introduce copolymerizable
groups. The enzymes were solubilized in organic solvents by the formation of
non-covalent ion pairs of enzymes and surfactants. The solubilized enzymes
were copolymerized in the organic phase via free radical polymerization with
hydrophobic monomers such as methyl methacrylate, styrene, vinyl acetate, and
ethyl vinyl ether, using trimethylol propane trimethacrylate or divinyl benzene
as crosslinker. The hybrid materials were used to synthesize peptides, sugars
and nucleotide esters in organic solvents such as THF and ethyl acetate. In later
work, the researchers extended the concept to more hydrophilic biocatalytic
plastics based on 2-hydroxyethyl methacrylate and examined the influence of
the chemical nature of the polymer on the enzymatic activity of α-chymotrypsin
in n-hexane (21). The activity correlates with the hydrophilicity of the polymer
and was found to be lowest for poly(methyl methacrylate)-based hybrid
materials and highest for poly(2-hydroxyethyl methacrylate)-based materials.
In an extension of the work on biocatalytic plastics, Kim, Dordick and Clark
reported the synthesis of biocatalytic films, coats, membranes and paints (22).
α-Chymotrypsin and pronase were incorporated into poly(dimethylsiloxane)
(PDMS)-based materials by dispersing enzymes entrapped in sol-gel particles
in solutions of silanol-terminated PDMS (without prior solvation of the enzyme
in organic solvents). Alternatively, enzymes were used that were modified with
3-aminopropyl triethoxy silane to provide chemical functionality that can react

with silanol-terminated PDMS. The PDMS/enzyme mixtures were subsequently
cured at room temperature by condensation of the PDMS‘s silanol groups and
with the curing agent tetramethyl orthosilicate and/or with the ethoxy silane
groups on the enzyme. The materials showed proteolytic activity and as a result
of this a reduced protein adsorption compared to materials that did not contain
any enzyme. Therefore, these coatings and paints could be used to reduce fouling
by proteins on surfaces. Biocatalytic silicone elastomers were also reported more
19
In Green Polymer Chemistry: Biocatalysis and Biomaterials; Cheng, H., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 2010.