Microbial Production of Bio-Based Chemicals: A Biorefinery Perspective

Sammanfattning: 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.