This PhD project within SYNFERON research project focuses on designing, constructing and characterizing a novel bioreactor which could overcome mass transfer limitations and achieve high cell density for efficient syngas fermentation to methane and alcohols.
The main challenges of the existing syngas fermentation technologies are the a) need of maintaining sterile conditions and b) mass transfer of sparingly soluble syngas compounds (CO, H2) to the water-based microbial cultures.
Therefore, the development of a fermentation system that could overcome mass transfer limitations and achieve high microbial cell density is important for efficient syngas fermentation. The most commonly used bioreactor configurations reported for fermentation of syngas include conventional stirred tank bioreactors, bubble columns, membrane reactors, trickling bed reactors and moving bed biofilm reactors.
The objective of this PhD project is the selection of an appropriate bioreactor configuration that could overcome mass transfer limitations and achieve high cell density for efficient syngas fermentation to methane and alcohols.
A novel reactor (combination of liquid-jet and packed bed) will be designed and constructed. The principal aim of the reactor design and operation will be the decrease of mass transfer limitations of the gas components to the liquid phase through spraying of the liquid growth medium into the gas phase (syngas) and the increased microbial cells (mixed microbial consortia not requiring sterile conditions) concentration due to the biofilm formation on the packed bed.
Contrary to the so far approaches of the distribution of micro-bubbles in the liquid phase, the suggested configuration will be based on the distribution of micro-droplets in the gas phase. In this project, the syngas fermentation efficiency of the liquid-jet reactor will be compared with that in the existing bio-film based reactors.
The effect of operational parameters, such as gas flow and pH, the selection of the appropriate packing material and the reactors’ configuration on the process efficiency will be tested in lab- and pilot-scale experiments.
Finally, part of the project will be the study of the structure and population distribution of the biofilm developed within the bioreactor. It is of high importance to identify the strains that prevail in the biofilm so as to assess their inherent capacity to produce the sought bio-products.
Main supervisor: Ioannis Skiadas
Co- supervisor: Hariklia Gavala