Biodegradation of Synthetic Polymers in the Aquatic Environment

209 Pages·2010·11.75 MB·English

by  Jan P. Eubeler

B S P
IODEGRADATION OF YNTHETIC OLYMERS IN
A E
THE QUATIC NVIRONMENT

Dissertation zur Erlangung des akademischen Grades eines Doktors der
Naturwissenschaften - Dr. rer. nat. - am Fachbereich II (Biologie/Chemie) der
Universität Bremen

Vorgelegt von Jan P. Eubeler
Bremen im April 2010
BIODEGRADATION OF SYNTHETIC POLYMERS IN THE AQUATIC ENVIRONMENT
1. Gutachter Hr. Prof. Dr. Rudolf Amann (Universität Bremen)
2. Gutachter Fr. Dr. Sabine Zok (BASF SE Ludwigshafen)
1. Prüfer Hr. Prof. Dr. Michael W. Friedrich (Universität Bremen)
2. Prüfer Hr. Prof. Dr. Thomas P. Knepper (Hochschule Fresenius, Idstein)

Termin des öffentlichen Kolloquiums:
21. Juni 2010, 13:30 Uhr, Alter Hörsaal, MPI für Marine Mikrobiologie, Celsiusstr. 1, Bremen

Eidesstattliche Erklärung
gem. § 6 (5) Nr. 1-3 Promotions-Ordnung der Universität Bremen vom 14 März 2007
Hiermit erkläre ich, das ich
die Arbeit ohne unerlaubte fremde Hilfe angefertigt habe,
keine anderen als die von mir angegebenen Quellen und Hilfsmittel benutzt habe und
die den benutzten Werken wörtlich oder inhaltlich entnommenen Stellen als solche kenntlich gemacht
habe.

Großkarlbach, den 01. April 2010

Jan P. Eubeler

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BIODEGRADATION OF SYNTHETIC POLYMERS IN THE AQUATIC ENVIRONMENT

"Bildung ist das, was übrig bleibt, wenn man alles vergessen hat, was man
gelernt hat. (…)"
(Werner Heisenberg)
„… und was man dann wiederum zu erlernen bereit ist.“

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BIODEGRADATION OF SYNTHETIC POLYMERS IN THE AQUATIC ENVIRONMENT

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BIODEGRADATION OF SYNTHETIC POLYMERS IN THE AQUATIC ENVIRONMENT
Acknowledgements
First of all, I would like to thank both my supervisor Dr. Sabine Zok (BASF SE) and Prof. Dr. Thomas P. Knepper
(Fresenius University of Applied Sciences) and my colleague and friend Dipl.-Ing. M. Bernhard for their help and
cooperation on this project and all related topics.
Furthermore I would like Prof. Dr. Allan D. Cembella (AWI Bremerhaven) for taking me as his doctoral student
and being my supervisor. I wish him all the best for recovering from his very unfortunate accident.
I also like to express my deepest gratitude to Prof. Dr. Rudolf Amann for taking over the position of Prof.
Cembella and supporting me through final phase of my dissertation. Thanks also to Prof. Dr. Michael W.
Friedrich for his expertise on my thesis. My gratitude goes also to Sara Kleindienst and Juliane Wippler for
being part of the committee.
I would like to express my gratitude especially to Helmut Schwarz, Stephan Hammer, Juergen Bachner, Karl-
Heinz Ullrich, Arnold “Lumpi” Gottwald, Helene Froehlich and Andy Haupt (GV/TC), for their support and help
every day in the Lab. Special thanks for the great time with you guys and the perfect Friday morning
“breakfast”. I will always remember that!
I am also most grateful to Dr. Christian Schütt and Hilke Döpke (BAH/AWI Helgoland/Bremerhaven) for the
cooperation, their intensive and unlimited help and the good weeks I spent at AWI BAH.
Special thanks go to Mrs. Frauke Ernst from University of Bremen. Thank you for your fast and constant support
in every administrative aspect.
I would like to thank BASF SE, especially GV/T as well as Mrs. Dr. Katrin Schwarz and her Team (E-EMV/Q) for
funding my project and for their support. It was a pleasure to work with you.
I also want to thank a lot of BASF staff for various help in my project:
Jens Kampioni for sending me all Pluriol E type and Pluriol E care samples, MSc Motonori Yamamoto for
supplying ECOFLEX, ECOVIO, MaterBi and PLA samples in various different versions. Thanks go as well to Dr.
Joachim Fischer, Dr. Inge Langbein, Dr. Klaus Taeger and Dr. Peter Reuschenbach for inspiring talks and ideas.
Thanks to Dr. Uwe Witt for supplying me with Oxo-PE samples and for discussions and literature and to Gert
Asselman from BTC Specialty Chemical Distribution N.V./S.A. Belgium for sending me samples of PEG &
MAPEG. Special thanks to Uwe Ruffer and Dr. Andrea Hörster from the Bioanalytical Department at BASF SE for
analyzing my marine samples. I also want to thank Prof. Dr. Andreas Künkel and his team for their input on my
review papers.
I want to express special gratitude also in the name of BASF to Mr. Wittner and his team at Luisenpark
Mannheim for their support and interest and for allowing myself to collect many, many seawater samples &

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BIODEGRADATION OF SYNTHETIC POLYMERS IN THE AQUATIC ENVIRONMENT
microorganisms from their aquarium! Also, I would like to thank those involved in sending seawater samples
from the North Sea near BASF Guesthouse at Sylt, Westerland to our laboratory for use in marine tests.
Thanks to Dipl.-Phil., Dipl.-Soz.-Päd. Sylvia Böttger from HS Fresenius, Idstein for her big support in my search
for literature. She has been always kind and never tired of sending me publications I could not get off the
Internet.
Thank you very much GDCh, SETAC, ASMS, DECHEMA e.V., ACS and all the other scientific societies. You were
all being very cooperative and supportive through all my time as an undergrad and grad student! This is
gratefully acknowledged and appreciated! Special Thanks to VCI/FCI for providing me with a scholarship for the
SETAG/GDCh PGS-Course in Ecotoxicology. The course is done very well and I would like to thank all involved
colleagues for their commitment.
All the people I have forgotten to mention here may please forgive me. You have also participated in this work
and you may remind me of that whenever you wish!
Last but not least I want to thank my mom and dad and also my grandparents for always listening and being
helpful and supportive. I am very grateful for many, many years of constant and unlimited support.
I would also like to thank Hendrik Jacob, Manuela Peschka, Matthias “Möcki” Möckl and Stefan Kappner, as
well as Holger Rinker, Frank Hess and Jürgen Diehl for the great hours we spent together (not only in the
“Promised Land”) having lots of fun! And thanks to the BOSS and all his colleagues and friends that have
delivered many days of beautiful reward being my winding wheel.

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Abstract
Biodegradation of synthetic polymers can be a sophisticated property for intelligent and sustainable products
that offer complex benefits for specific applications. There are many entry paths for synthetic polymers that
can accumulate in the aqueous and especially marine environment and little is known about their
biodegradation especially in the aquatic environment. The difficulties with determining biodegradation in those
environments are based on the absence of appropriate methods and also the fact that these environments
often prove low biodegradation rates. It is also complicated to detect biodegradation on polymeric substances
because of the high molecular weight, water insolubility and difficult molecular structure making it hard to
detect biodegradation products.
This work provides an overview of the actual status of research regarding biodegradation, results and methods
describing biodegradation of biodegradable polymers. The main focus of this study is to find out if standard
biodegradation tests may be used for the evaluation of polymer biodegradation. Its aim is to identify difficulties
and problems with these tests and to compare the biodegradation potential and biodegradation pathways in
the marine and freshwater environment for a selection of polymer types.
It is also investigated whether molecular or structural properties of the polymers influence the biodegradation
in different environments and the possible pathways of biodegradation. Similarities and differences are
identified and on a selection of the biodegradation tests an investigation of the microorganism community is
performed to evaluate the use of molecular methods to discover influences of microorganisms on the
biodegradation of polymers.
Investigating available methods on how evaluation of biodegradation can be performed best in this special field
is a first step in a new direction. It may be important for further development of representative test
procedures. First facts on how biodegradation can be determined under the special circumstances are
established based on standardized methods which are adapted to the requirements
Three different types of carefully selected polymers and their degradation behaviour are evaluated based on
OECD test guidelines. Compounds were selected based water solubility/insolubility and biodegradation
potential:
∙ Poly(vinyl pyrrolidone) is selected because it is known to be recalcitrant and is investigated to observe
differences and similarities in different tests and media when no biodegradation can be observed
(“negative control”).
∙ Poly(ethylene glycol), a water soluble biodegradable polymer is investigated in broad molecular
weight distribution ranging from molecular weights of 200 to almost 60’000 g∙mol-1. Data from
different aquatic compartments are compared to establish differences systematically.

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∙ The water insoluble biodegradable polyesters Ecoflex® and Ecovio® are investigated focusing mostly
on marine environment. In these cases the biodegradation potential as well as similarities and/or
differences between aqueous and compost environments (where they are known to be
biodegradable) are the main aspects of the study.
Both water soluble polymers are important mass production products that are used in manifold applications
and that also have higher potential to enter the aquatic environment from their applications and products
directly or indirectly.
The biodegradation of poly(ethylene glycol) especially shows the importance of systematic investigations and
the possibilities in application of the available test methods. It was shown that there are major differences
between freshwater (activated sludge, OECD 301) tests and those in marine (synthetic and native marine
water) tests. The differences range from the time of biodegradation of the same substances to differences in
the biodegradation graphs of reference substances and also to differences in the metabolic pathway as is
shown with sophisticated analytical techniques. The potential of biodegradation freshwater and marine tests is
shown for the first time systematically for the group of poly(ethylene glycols) ranging from 200 to almost
60’000 g∙mol-1. This data shows differences in the applied methods and also the applicability of the marine
tests. As shown in the figure below there are significant differences of biodegradation in both test media (here:
activated sludge and sea water) and between the biodegradation curves based on the different types
measurement parameters (carbon dioxide evolution and dissolved organic carbon).

Biodegradation of poly(ethylene glycol) (4500 g⋅mol-1) in activated sludge and marine biodegradation tests

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It is shown in this study that poly(ethylene glycol) biodegrades up to a specific molecular weight in freshwater
and marine environment after certain time to full extent (up to 60 kDa in freshwater and 15 kDa marine water).
Poly(ethylene glycol) biodegradation is investigated for the first time to this extend and biodegradation
pathways are postulated with the help of sophisticated analytical methods as shown in the figure below. It
seems interesting, that there are obviously two different pathways in marine water for poly(ethylene glycol) of
approximately <1600 g∙mol-1 and for poly(ethylene glycol) of approximately >1600 g∙mol-1. It also seems
interesting that some microorganisms prefer lower substrate concentration and related biodegradation degree
is lower when increased substance concentrations are used. Different pathways for the biodegradation were
established depending on molecular weight distribution as shown in the following figure.

Pathways for poly(ethylene glycol) degradation in freshwater and seawater
The results obtained from the complex studies in this work show that the international guidelines can be in
some cases applied directly in other cases need to be adapted.
Neither the criteria from OECD 301 biodegradation tests nor those from OECD 306 tests are appropriate for
biodegradation tests of synthetic polymers. The test duration is in most cases too short especially for marine
biodegradation. Many substances that are degradable will fail to pass the test criteria even though they are not
recalcitrant. Longer tests but below 200-300 days provide more insight with better reproducibility. It is often
helpful when analytical tools are available to determine specifically the polymers tested and it is required that
more than one parameter is measured to gain more reliable data. However, it seems that marine tests take

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much longer than other environmental biodegradation or simulation tests. This is disadvantage for these tests
in any application.
Also molecular or structural properties of the polymers do influence the biodegradation in different
environments as well as number of hetero atoms in the chain, specific behaviour of groups that hydrolize but
do not biodegrade etc. Possible pathways of biodegradation are confirmed and similarities and differences are
identified which supports some of the known statements in published literature on other biodegradation
research projects mostly in solid media.
In summary the following statements based on the biodegradation results especially with synthetic polymers,
can be made:
∙ Biodegradation in standard test systems and marine test systems can differ in kinetics and pathway of
biodegradation.
∙ The tests using CO free air in closed systems give stable conditions and variations can be kept low
2
during the first 200-300 days.
∙ Because of the immense buffer capacity of marine sea water generally higher blank control values as
well as much more variation has been observed in the tests when compared with OECD 301 standard
tests.
∙ The desired type of analytical procedure (DOC/DIC; BOD, CO ) determines the length of the study and
2
needs to be considered. If possible more than one parameter should be measured at the same time.
∙ Marine tests show mainly far lower biodegradation when compared to freshwater/WW and soil or
compost.
∙ Marine medium can be prepared synthetically in the lab or native sea water can be used if treated
carefully and water samples should be stored at constant temperature.
∙ Tests using native water may have more impact and are closer to natural conditions but no significant
differences were observed compared to synthetic medium in this study.

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