Control of Oxidative Sulfur Metabolism of Chlorobium limicola forma thiosulfatophilum

Abstract

A metered blend of anaerobic-grade N2, CO2, and H2S gases was introduced into an illuminated, 800-ml liquid volume, continuously stirred tank reactor. The system, described as an anaerobic gas-to-liquid phase fed-batch reactor, was used to investigate the effects of H2S flow rate and light energy on the accumulation of oxidized sulfur compounds formed by the photoautotroph Chlorobium limicola forma thiosulfatophilum during growth. Elemental sulfur was formed and accumulated in stoichiometric quantities when light energy and H2S molar flow rate levels were optimally adjusted in the presence of nonlimiting CO2. Deviation from the optimal H2S and light energy levels resulted in either oxidation of sulfur or complete inhibition of sulfide oxidation. Based on these observations, a model of sulfide and sulfur oxidases electrochemically coupled to the photosynthetic reaction center of Chlorobium spp. is presented. The dynamic deregulation of oxidative pathways may be a mechanism for supplying the photosynthetic reaction center with a continuous source of electrons during periods of varying light and substrate availability, as in pond ecosystems where Chlorobium spp. are found. Possible applications for a sulfide gas removal process are discussed.

Continuous Feed Microbial Fuel Cell Using An Air Cathode and A Disc Anode Stack for Wastewater Treatment

“…normally grow in environments rich in hydrogen sulphide, which they use as electron donor to generate reducing power for biosynthesis and produce elemental sulfur as a product of sulfide oxidation. In addition, they can photo-oxidize hydrogen as well as other sulfur compounds such as sulphide, polysulfide, and thiosulfate. , Fermentation of organic matter and sulfate reduction are potential sources of methane in the MFC, however the sulfate concentrations were approximately 0.5 mM and were unlikely to sustain high levels of sulfide generation. Fermentation of organic matter may therefore be the most likely source of sulfide in the MFC system.…”

Photoautotrophic removal of hydrogen sulfide from biogas using purple and green sulfur bacteria

“…The higher OD 650 in A. vinosum tests likely explain the steady increase in SO C. limicola was probably mediated by sulfide underloading as described by the theory of the "van Niel curve" (Cork et al, 1985). This theory hypothesizes three potential sulfide metabolization scenarios in phototrophic sulfur bacteria based on the relationship between sulfide loading rate and light intensity: i) a balanced state where all sulfide is oxidized to sulfur without formation of SO 4 2-, ii) sulfide overloading, where sulfide accumulates in the medium due to an insufficient light energy supply, iii) sulfide underloading, where the demand for electron donor exceeds its supply (low sulfide loading) and consequently sulfate is formed from elemental sulfur according to Eq.…”

“…The creation of intracellular sulfur globules due to the high abundance of H 2 S also contributed to this increase in culture absorbance (Kushkevych et al, 2021b). However, this rapid increase in OD 650 also supported a fast H 2 S removal, resulting in the use of stored sulfur as an electron donor (Cork et al, 1985). On the other hand, C. limicola exhibited a moderate increase in absorbance after the addition of H 2 S, which continued until the end of the experiment due to a slow assimilation of H 2 S. The lower OD 650 in C. limicola tests entailed that the replenished H 2 S was enough to cover the electron donor requirements.…”

Desulphurisation of Biogas: A Systematic Qualitative and Economic-Based Quantitative Review of Alternative Strategies

“…The van Niel curve (adapted from[130]). Biological desulphurisation via phototropic bacteria activity for H2S removal occurs according to the general equation below[128,129];…”