Formic Acid Formation by Clostridium ljungdahlii at Elevated Pressures of Carbon Dioxide and Hydrogen

Abstract

Low productivities of bioprocesses using gaseous carbon and energy sources are usually caused by the low solubility of those gases (e.g., H2 and CO). It has been suggested that increasing the partial pressure of those gases will result in higher dissolved concentrations and should, therefore, be helpful to overcome this obstacle. Investigations of the late 1980s with mixtures of hydrogen and carbon monoxide showed inhibitory effects of carbon monoxide partial pressures above 0.8 bar. Avoiding any effects of carbon monoxide, we investigate growth and product formation of Clostridium ljungdahlii at absolute process pressures of 1, 4, and 7 bar in batch stirred tank reactor cultivations with carbon dioxide and hydrogen as sole gaseous carbon and energy source. With increasing process pressure, the product spectrum shifts from mainly acetic acid and ethanol to almost only formic acid at a total system pressure of 7 bar. On the other hand, no significant changes in overall product yield can be observed. By keeping the amount of substance flow rate constant instead of the volumetric gas feed rate when increasing the process pressure, we increased the overall product yield of 7.5 times of what has been previously reported in the literature. After 90 h of cultivation at a total pressure of 7 bar a total of 4 g L−1 of products is produced consisting of 82.7 % formic acid, 15.6 % acetic acid, and 1.7 % ethanol.

Regulation of Vascular Calcification by Reactive Oxygen Species

“…Several resident and circulating cell types can undergo osteogenic differentiation/transdifferentiation upon osteogenic stimulation and, therefore, can be involved in vascular calcification. These cells include vascular smooth muscle cells (VSMCs), smooth muscle- and endothelial cell progenitors, pericytes, and adventitial cells, as well as circulating mesenchymal and hematopoietic stem cells [ 39 ]. In this review, we will focus on osteogenic/osteochondrogenic transdifferentiation of VSMCs because this is the most extensively studied mechanism and the most widely accepted theory to explain vascular calcification.…”

Life Cycle Assessment of Microbial Electrosynthesis for Commercial Product Generation

“…Wood-Ljungdahl pathway for the synthesis of other chemicals (Oswald et al, 2018). Therefore, the chemical could be used as substrate by other formate consuming bacteria species attached to the biocathode after generation.…”

Gas Fermentation Expands the Scope of a Process Network for Material Conversion

“…Understanding the effects of different gases on LGS fermentation processes is crucial in optimizing gas compositions to achieve a desired product range. In fermenter-scale experiments, the influence of an increased headspace pressure was evaluated [108,[148][149][150]. Oswald et al demonstrated that an increase in pressure of up to 7 bar for LGS fermentations with C. ljungdahlii growing solely on CO 2 and H 2 led to a shift in the product spectrum [149].…”

“…Additionally, methanol and formate can be produced in LGS fermentation (Fig. 1, M and N) [95,149]. Methanol is considered a key molecule in methane-based biorefinery [95].…”