Bio-based C-3 Platform Chemical: Biotechnological Production and -Conversion of 3-Hydroxypropionaldehyde
Abstract: Popular Abstract in English Microbes are present everywhere in the environment and have quite an intimate relationship with humans. Much of our perception about microbes is as disease causing agents but on the other hand it is also the microbes that present cure for the disease. Besides using microbes for traditional applications, for example for providing antibiotics, production of fermented foods, etc., humans are increasingly taking advantage of the ”good” microbes as probiotics for improving health, wastewater treatment, mining of metals, cleaning the environment, and for producing bioenergy, chemicals and materials. The micro-sized organisms contain a complex network of metabolic pathways involving a large number of chemical reactions catalysed by enzymes for utilizing different substances in the environment and converting them to a variety of products. Lactic acid bacteria comprise an important group of microbes that humans have used for thousands of years to conserve and enhance the nutritional value of sensitive foods. Lactobacillus species are a major part of this group. Some Lactobacillus species are used for the production of yoghurt, cheese, sauerkraut, pickles, beer, wine, cider several fermented foods, as well as animal feeds, such as silage. Lactobacillus reuteri is a major component of the bacteria present in guts of mammals and birds. It has been shown that several different strains of L. reuteri have a positive effect on health, including various types of gastrointestinal disorders and oral health. In the late 1980s, it was discovered that L. reuteri produced a novel broad-spectrum antibiotic substance by fermentation of glycerol, which was named as "reuterin” after Gerhard Reuter. Reuterin can inhibit the growth of some harmful Gram-negative and Gram-positive bacteria, along with yeasts, fungi and protozoa. Reuterin is a mixture of three components, made of 3-hydroxypropionaldehyde (3HPA) and its derivatives. This thesis is about 3HPA as a molecule of interest for the chemical industry based on renewable resources. Today, as we become increasingly aware of our dependence on fossil resources to fulfill our needs, and the environmental problems associated with the use of these non-renewable resources, there is a growing interest in the use of renewable resources as raw materials and environment-friendly methods for the production of chemicals, materials and energy. 3HPA is currently not a commercial product. If it could be economically produced from glycerol using the bacteria it can potentially be used as a building block or ”platform” for several other chemicals with 3 carbon atoms (C3), e.g. 1,3-propanediol (1,3PDO), 3-hydroxypropionic acid (3HP), acrolein, etc. Glycerol, commonly known as glycerine, is produced as a side product of hydrolysis of fats, production of ethanol and biodiesel. Over the past decade or more, biodiesel is being produced from several plant oils such as rapeseed-, soybean- and palm oil, and also from used oils. In this thesis, conversion of glycerol to 3HPA using L. reuteri is investigated. When the 3HPA level reaches a certain limit, it starts to affect the cell viability and activity, hence inhibiting its own production. Different strategies to complex 3HPA were studied to improve its production. L. reuteri has also the ability to convert 3HPA to 1,3PDO and 3HP via different pathways. In the thesis, the pathway for 3HP production has been introduced in standard bacteria, Escherichia coli by recombinant DNA technology and shown to be active. One of the enzymes of the pathway has further been studied. The work in this thesis was done in collaboration with Perstorp AB, and was supported by Vinnova, the Swedish Governmental Agency for Innovation Systems.
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