Microbial production of 3-hydroxypropionic acid and poly(3-hydroxypropionate): Investigation of Lactobacillus reuteri propanediol utilization pathway enzymes
Författare
Summary, in Swedish
Popular Abstract in English
Since the onset of the 20th century, human society has been using non-renewable
resources, mainly oil, for the production of fuels and chemicals that are now an
integral part of our everyday life. In the last few decades however, concerns regarding
environmental effects, geopolitical issues and the eventual depletion of oil have led to
us re-evaluating our dependency on this resource. Current production of a majority of
everday chemicals is based on refining petroleum to a small number of other
molecules, also known as platform chemicals, which can then be converted to a much
larger number of chemicals through various processes.
In our efforts to move from a fossil to biobased economy in which renewable
resources like sugars or glycerol, obtained through plants, trees, grasses, and/or as
residues/wastes of agro-/forestry based industries, will constitute the feedstock for
industry, sustainable technologies for processing of the biomass and its components in
an environmentally-friendly manner need to be develooped. Biotechnological
production of platform chemicals from the biomass feedstocks is mainly based on
replacing traditional chemical reactors with microorganisms. Microorganisms can be
considered small reactors as they contain mechanisms for the conversion of a large
variety of natural as well as synthetic molecules to others. These mechanisms are
driven by enzymes which are in turn encoded in their genomes. As microorganisms
are present in pretty much every type of environment imaginable on the planet, the
number of naturally occurring reactions is very high. Some microorganisms are
known to produce biodegradable plastics as a protection mechanism in harsh
conditions. Microbial processes for the production of chemicals and materials are
based in water and require no organic solvents. They can be performed in lower
temperatures and are very specific. As petroleum is cheap however, there is no
economic incentive to shift to these greener processes. Thus, it is important to
develop microbial methods for the production of these chemicals from cheap
resources and in high concentrations and yields.
This thesis deals mainly with the production of the platform chemical 3-
hydroxypropionic acid (3-HP) and its polymer poly(3-hydroxypropionate). These
products are not available commercially. 3-HP is of great promise as it can be further
converted into wide array of chemicals, e.g. resins, coatings, lubricants and in the
textile industry as anti-static agent. Poly(3-HP) is a biodegradable polymer that can
replace certain fossil-based polymers in different applications.
3-HP is produced in smaller amounts by certain microorganisms that grow slowly
and/or are expensive to cultivate. Therefore, a copy and paste-strategy has been
implemented for moving some of the reactions to well-known organisms that are
easier and cheaper to cultivate. Lactobacillus reuteri, a probiotic bacteria, contains a
mechanism for the production of 3-hydroxypropionic acid from glycerol, which is
currently produced in large amounts as a byproduct from the production of bio-diesel
from several plant oils. By copying relevant genes and transferring them to the
cheaply cultivated bacterium Escherichia coli, it was proven that 3-HP could be
produced with a high yield from glycerol. Such a strategy does require the
understanding of the metabolic system in the bacteria in order to avoid any
interference and to incorporate strategies for improving the formation of the product
in a selective and clean manner. Such strategies were implemented in the present
work, thereby increasing the final concentration of 3-HP. Some key enzymes in these
processes were studied further in order to gain a better understanding of their
function and structure.
It the same manner, a relevant gene from Lactobacillus reuteri and a gene from
another bacteria, Chromobacterium sp. known to produce a bioplastic, were copied
and pasted in Escherichia coli, resulting in a strain with the capacity to produce
poly(3-hydroxypropionate) in a cheap and efficient manner.
Since the onset of the 20th century, human society has been using non-renewable
resources, mainly oil, for the production of fuels and chemicals that are now an
integral part of our everyday life. In the last few decades however, concerns regarding
environmental effects, geopolitical issues and the eventual depletion of oil have led to
us re-evaluating our dependency on this resource. Current production of a majority of
everday chemicals is based on refining petroleum to a small number of other
molecules, also known as platform chemicals, which can then be converted to a much
larger number of chemicals through various processes.
In our efforts to move from a fossil to biobased economy in which renewable
resources like sugars or glycerol, obtained through plants, trees, grasses, and/or as
residues/wastes of agro-/forestry based industries, will constitute the feedstock for
industry, sustainable technologies for processing of the biomass and its components in
an environmentally-friendly manner need to be develooped. Biotechnological
production of platform chemicals from the biomass feedstocks is mainly based on
replacing traditional chemical reactors with microorganisms. Microorganisms can be
considered small reactors as they contain mechanisms for the conversion of a large
variety of natural as well as synthetic molecules to others. These mechanisms are
driven by enzymes which are in turn encoded in their genomes. As microorganisms
are present in pretty much every type of environment imaginable on the planet, the
number of naturally occurring reactions is very high. Some microorganisms are
known to produce biodegradable plastics as a protection mechanism in harsh
conditions. Microbial processes for the production of chemicals and materials are
based in water and require no organic solvents. They can be performed in lower
temperatures and are very specific. As petroleum is cheap however, there is no
economic incentive to shift to these greener processes. Thus, it is important to
develop microbial methods for the production of these chemicals from cheap
resources and in high concentrations and yields.
This thesis deals mainly with the production of the platform chemical 3-
hydroxypropionic acid (3-HP) and its polymer poly(3-hydroxypropionate). These
products are not available commercially. 3-HP is of great promise as it can be further
converted into wide array of chemicals, e.g. resins, coatings, lubricants and in the
textile industry as anti-static agent. Poly(3-HP) is a biodegradable polymer that can
replace certain fossil-based polymers in different applications.
3-HP is produced in smaller amounts by certain microorganisms that grow slowly
and/or are expensive to cultivate. Therefore, a copy and paste-strategy has been
implemented for moving some of the reactions to well-known organisms that are
easier and cheaper to cultivate. Lactobacillus reuteri, a probiotic bacteria, contains a
mechanism for the production of 3-hydroxypropionic acid from glycerol, which is
currently produced in large amounts as a byproduct from the production of bio-diesel
from several plant oils. By copying relevant genes and transferring them to the
cheaply cultivated bacterium Escherichia coli, it was proven that 3-HP could be
produced with a high yield from glycerol. Such a strategy does require the
understanding of the metabolic system in the bacteria in order to avoid any
interference and to incorporate strategies for improving the formation of the product
in a selective and clean manner. Such strategies were implemented in the present
work, thereby increasing the final concentration of 3-HP. Some key enzymes in these
processes were studied further in order to gain a better understanding of their
function and structure.
It the same manner, a relevant gene from Lactobacillus reuteri and a gene from
another bacteria, Chromobacterium sp. known to produce a bioplastic, were copied
and pasted in Escherichia coli, resulting in a strain with the capacity to produce
poly(3-hydroxypropionate) in a cheap and efficient manner.
Avdelning/ar
- Biotechnology
Publiceringsår
2015
Språk
Engelska
Fulltext
Dokumenttyp
Doktorsavhandling
Förlag
Division of Biotechnology, Lund University
Ämne
- Industrial Biotechnology
Nyckelord
- Platform chemicals
- biopolymers
- 3-hydroxypropionic acid
- 3-hydroxypropionaldehyde
- glycerol
- poly(3-hydroxypropionate)
- polyhydroxyalkanoates
- Escherichia coli
- Lactobacillus reuteri
- propanediol utilization pathway
- propionaldehyde dehydrogenase
- biotransformation
- cofactor regeneration
- NADH oxidase
Aktiv
Published
Handledare
- Rajni Hatti-Kaul
- Javier Linares-Pastén
- Shukun Yu
ISBN/ISSN/Övrigt
- ISBN: 978-91-7623-274-3
Försvarsdatum
30 april 2015
Försvarstid
10:00
Försvarsplats
Lecture hall B, Kemicentrum, Getingevägen 60, Lund University, Faculty of Engineering LTH, Lund
Opponent
- An-Ping Zeng (Professor)