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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.

Avdelning/ar

Publiceringsår

2015

Språk

Engelska

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

Status

Published

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