Establishment and optimization of a power-to-food system to produce single cell protein containing cobalamin and folate

Abstract

At the beginning of this thesis, we illustrate the power-to-protein concept by conducting a comparative analysis between all the systems that have been implemented to perform carbon fixation into microbial protein using renewable power. The comparison was conducted using the principles of thermodynamics on the predominant carbon fixation pathways used by the microbes involved in each system. It revealed that a two-stage system in which carbon dioxide is first converted to an intermediate, and then presented to a different bioreactor as a substrate for synthesizing microbial protein, would yield the highest biomass per unit input energy. Following this, we demonstrate its operation in a proof-of-concept study, in which the first bioreactor was operated with Clostridium ljungdahlii to convert carbon dioxide into acetic acid through the Wood-Ljungdahl pathway. This new carbon source was provided to the second bioreactor for the growth of an aerobic strain of yeast, Sachharomyces cerevisiae to synthesize microbial protein. As this strain has already been accepted for human consumption, evidence of its growth on acetic acid renders a big advantage to the proposed system. In this operation, 25% of the total carbon from carbon dioxide was converted into yeast biomass with a protein content of 40-50%.