Exploring Anaerobic Bacteria for Industrial Biotechnology - Diversity Studies, Screening and Biorefinery Applications
Abstract: Depletion of easily accessible fossil energy resources, threat of climate change and political priority to achieve energy self-sufficiency and sustainable solutions prioritize a conscious and smart use of renewable resources to generate a bio-based economy. Bio-based compounds can replace chemicals and fuels that are now mainly produced from crude oil. Efficient processes for the conversion of plant biomass into compounds of interest to the biorefinery industry occur naturally in anaerobic environments such as in the forestomach of herbivores. Exploration of anaerobic microorganisms for industrial biotechnological applications creates the possibility to convey efficient and flexible processes, with lower implementation and running costs, making it also applicable to developing and emerging economies. Despite the growing interest in anaerobic microorganisms for applications in industrial biotechnology, there is less information available concerning their diversity and function compared to what is known for their aerobic counterparts. To counter this, microbial diversity studies on an unexplored environment for microbial applications, was investigated by molecular and traditional cultivation techniques. The bacterial diversity of the forestomach of the llama, showed differences in the prokaryotes populations according to the complexity of the material type digested. Bacterial isolates were selected by their ability to produce compounds such as organic acids and alcohols and hydrolytic enzymes. Also, a new strategy for cultivation of anaerobic microorganisms with the potential for an improved isolation rate and screening has been developed in this thesis work. The technique is based on single cell entrapment in alginate microbeads. A method was optimized for simple preparation under anaerobic conditions and successful cultivation of single cells was observed. Further applications of anaerobic bacteria towards the biorefinery were also studied. The production of 1,3-propanediol, a compound used as building block for polymer materials, was investigated from selected llama isolates. The use of wheat straw as co-substrate and/or support material improved the concentration of 1,3-propanediol by 29% for C. butyricum BSL59 and 65% for C. butyricum BSL61 in comparison to using sole glycerol in the medium. The use of wheat straw was also superior in comparison to addition of pure sugars. Moreover, the solid residue from sequence batch fermentation using wheat straw as co-substrate showed to have high methane potential yield. Demonstrating that agriculture residue can be used in an integrated process for the production of valuable chemical compounds and energy carriers. Finally, a new method for cell immobilization forming a macroporous material was evaluated for butanol production which reaches high yields and allows repeated use of the cell-based material.
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