Microbial Production of Bio-Based Chemicals: A Biorefinery Perspective

Abstract

A shift from fossil- to renewable biomass feedstock for the emerging bio-based economy requires the development and adoption of new sustainable technologies that are more suited for transformation of biomass components to chemicals, materials and energy. This thesis presents investigations on the development of processes based on industrial biotechnology as a key element for the production of chemicals from agro-/industrial by-products. The chemicals of interest are the ones that could potentially serve as building blocks, platforms, for other chemicals and polymers. Glycerol, a by-product of biodiesel production, was used as raw material for the production of propionic acid, 3-hydroxypropionaldehyde (3HPA) and 3-hydroxypropionic acid (3HP), while methacrylic acid (MA) was produced from 2-methyl-1,3-propanediol, a by-product of butanediol production. Different strategies to overcome the bottlenecks such as product inhibition existing in the bioprocesses for production of the chemicals were studied.

Fermentation of glycerol to propionic acid was studied using Propionibacterium acidipropionici. High cell density cultivations were used to overcome the low production rate caused by slow microbial growth and product-mediated toxicity. Increasing the cell density by immobilization and sequential batch recycling improved the production rates by 2- and 6-fold, respectively, over that obtained using conventional batch fermentation. Potato juice, a by-product of potato starch processing, was shown to be a promising, inexpensive nitrogen/vitamin source for the growth of the organism and propionic acid production.

Lactobacillus reuteri was employed as a whole cell biocatalyst for the conversion of glycerol to 3HPA and 3HP in aqueous solution. Production of 3HPA using glycerol dehydratase activity of the cells, limited by substrate inhibition and product toxicity, was performed in a fed-batch mode with in situ complexation of the hydroxyaldehyde with bisulfite, and subsequent removal through binding to an anion exchanger. This resulted in increase in production of 3HPA from 0.45 g/g biocatalyst in a batch process to 5.4 g/g. 3HP is formed as an oxidation product of 3HPA, however its accumulation as a product of glycerol metabolism in wild-type L. reuteri has not been reported earlier. The metabolic fluxes through the glycerol reductive and oxidative pathways were calculated using variable volume fed-batch operation. The glycerol feeding strategies were optimized to yield complete conversion of 3HPA into equimolar mixture of 3HP and 1,3PDO, the products that can be easily separated from each other.

MA was quantitatively produced at high purity from 2-methyl-1,3-propanediol by a novel process involving integrated biological and chemical catalysis. Whole resting cells of Gluconobacter oxydans were used for selective oxidation of the substrate to the corresponding hydroxycarboxylic acid, which upon dehydration over TiO2 at 210 degree Celsius yielded MA. This process offers a potential, significantly greener alternative to the acetone-cyanohydrin process used for MA production, involving highly toxic substrates, large amounts of waste and greenhouse gas emissions.

Abstract (Swedish)

Popular Abstract in English

A large variety of microorganisms are present in nature and have indispensable roles in recycling carbon, remediation of the environment, agriculture, and also in providing health benefits to humans. Microorganisms are microscopic versatile living factories that can consume several different natural as well as synthetic compounds for their growth and also produce different useful chemicals. Microorganisms have long been used for production of cheese, wine, antibiotics such as penicillin, fuels such as ethanol, amino acids and other chemicals such as citric acid and acetic acid. However, majority of the chemical products we use in our daily lives are made from fossil resources in petrochemical refineries. These chemicals are used in foods, animal feed, pharmaceuticals, cosmetics, agriculture, paints, coatings, plastics and many more applications.

The increasing price of mineral oil and gas during the past few decades has led to a concern that fossil resources will come to an end and will not sustain the needs of the growing population. On the other hand, the fossil products are said to have a negative effect on the environment, and have contributed to global warming, pollution of soil and waters, and climate change. With the increased concern about the environment and sustainability, there is growing demand for alternative renewable raw materials for chemicals and energy and for cleaner processes that do not burden the environment. Organic biomass, e.g. from plants and trees, and also side products from different industries provide useful renewable raw materials for production.

This thesis provides evidence that microorganisms can be used to produce important industrial chemicals from side-products of existing industrial processes. In some cases, they provide an alternative route for an existing chemical, while in the others the chemicals not yet available in the market are produced. The target chemicals would serve as building blocks for other chemicals and polymers in the industry based on renewable raw materials. The focus in the thesis has been to overcome the bottlenecks in the microbial systems so as to make them economical for industrial production of chemicals.

Examples of the industrial side-products used in the present thesis are glycerol (glycerine), which is formed during production of biodiesel from vegetable oil, and potato juice, a liquid stream produced during extraction of starch from potatoes. Glycerol is used as a source of carbon by different bacteria and is converted to different important chemicals. Among the bacteria used in the work are Propionibacteria used in cheese making, and lactobacillus used as a probiotic.

• author: Dishisha, Tarek
• supervisor: Rajni Hatti-Kaul; Sang-Hyun Pyo; Per Persson
• opponent: Professor Yang, Shang-Tian, Department of Chemical and Biomolecular Engineering, Director, Ohio Bioprocessing Research Consortium, The Ohio State University, USA
• organization: Biotechnology
• publishing date: 2013
• type: Thesis
• publication status: published
• subject: Industrial Biotechnology
• keywords: Biorefinery, platform chemical, organic acid, propionic acid, 3-hydroxypropionic acid, 3-hydroxypropionaldehyde, methacrylic acid, 1, 3-propanediol, Propionibacterium acidipropionici, Lactobacillus reuteri, Gluconobacter oxydans, high cell density fermentation, biotransformation, product inhibition, cell recycle, immobilized cells, chemical catalysis, pdu operon
• categories: Higher Education
• pages: 154 pages
• defense location: Lecture Hall B at the Center for Chemistry and Chemical Engineering, Sölvegatan 39, Lund
• defense date: 2013-06-11 13:30:00
• ISBN: 978-91-89627-92-5
• language: English
• LU publication?: yes
• additional info: Author alternative e-mails: [e-mail] - [e-mail]
• id: 93a4e3ce-eff5-4db1-bde3-6efa9adb18a1 (old id 3738373)
• date added to LUP: 2016-04-04 13:39:50
• date last changed: 2023-04-18 18:08:43