Sulfur compounds biological oxidation

Isotope effects also play an important role in the distribution of sulfur isotopes. The common state of sulfur in the oceans is sulfate and the most prevalent sulfur isotopes are (95.0%) and (4.2%). Sulfur is involved in a wide range of biologically driven and abiotic processes that include at least three oxidation states, S(VI), S(0), and S(—II). Although sulfur isotope distributions are complex, it is possible to learn something of the processes that form sulfur compounds and the environment in which the compounds are formed by examining the isotopic ratios in sulfur compounds. 

As seen in the above equations, the aqueous oxidation processes convert sulfur in the feed to dissolved sulfate, while arsenic is oxidized and precipitated as ferric arsenate compounds. So, problems of the emission of sulfur and arsenic oxides caused by roasting are avoided in the aqueous oxidation processes. The two different industrial methods which achieve the oxidation reactions are pressure oxidation and biological oxidation. 

Sorokin, D. Y., Biological Oxidation of Sulfur Atoms in Cl-Sulfur and Other Organosulfur Compounds. Microbiology (NY), 1993. 62(6) pp. 575-581. 

Ishio, M. Fujii, M., and Matsubara, S., Culture and growth of microorganism capable of oxidizing and decomposing sulfur compound contained in petroleum and biological desulfurization Patent No. JP7111900. 1995, May 02. 

Many organosulfur compounds undergo biological oxidation at the sulfur atom to yield products which have pronounced physiological activity or serve as intermediates in generating bioactive compounds. Three examples are the lachrymating agent in onions ( ) (1), the oxo intermediate ( ) in metabolic desulfuration of phosphorothionate insecticides to form potent cholinesterase inhibitors (2), and the sulfoxides QJ produced on metabolism of thiocarbamate herbicides (3). 

As discussed in Chapter 2 and in more detail in Chapter 11, a variety of organic sulfur compounds in addition to inorganics such as H2S and COS are emitted by biological sources. In the troposphere, they may ultimately be oxidized to S02 and H2S04. However, the chemistry of these compounds tends to be complex, and a variety of partially oxidized sulfur compounds is formed first. 

In addition to the primary product and by-product streams, sulfur will be present in other streams in the facility. For example, water that is condensed from the product will contain some dissolved sulfur compounds, as will the stack from the boiler house that is required to provide steam for the system. Dissolved sulfur gases will normally be stripped from foul water to the gas streams, but some fixed sulfur (e.g. thiocyanate) may not be attacked until biological oxidation or other water treatment. The sulfur compounds present in the boiler house stack might be recovered to salable products, depending on the flue gas desulfuri-... 

SULFUR (In Biological Systems). Sulfur, in some form, is required by all living organisms. It is utilized in various oxidation stales, including sulfide, elemental sulfur, sulfite, sulfate, and thiosulfate by lower forms and in organic combinations by all. The more important sulfur-containing organic compounds include the amino acids (cysteine, cystine, and methionine, which are components of proteins) the vitamins thiamine and... 

The anaerobic metabolism of acrylate and 3-mercaptopropionate (3-MPA) was studied in slurries of coastal marine sediments. The rate of these compounds is important because they are derived from the algal osmolyte dimethylsulfoniopropionate (DMSP), which is a major organic sulfur compound in marine environments. Micromolar levels of acrylate were fermented rapidly in the slurries to a mixture of acetate and propionate (1 2 molar ratio). Sulfate-reducing bacteria subsequently removed the acetate and propionate. 3-MPA has only recently been detected in natural environments. In our experiments 3-MPA was formed by chemical addition of sulfide to aciylate and was then consumed by biological processes. 3-MPA is a known inhibitor of fatty acid oxidation in mammalian systems. In accord with this fact, high concentrations of 3-MPA caused acetate to accumulate in sediment slurries. At lower concentrations, however, 3-MPA was metabolized by anaerobic bacteria. We conclude that the degradation of DMSP may ultimately lead to the production of substrates which are readily metabolized by microbes in the sediments. 

Dimethyl Sulfide. DMS is one of the major reduced sulfur compounds produced by biological activity, mainly in the oceans (2.3). For this reason its oxidation reactions have been intensively studied, especially the reaction... 

Reduced sulfur compounds are ubiquitous in aqueous and atmospheric systems (10,11). Natural sources of reduced sulfur species in aqueous environment result from biological reduction of sulfate, anaerobic microbial processes in sewage systems, putrefaction of sulfur-containing amino-acids (12), oxidative decomposition of pyrite (13), and activities of marine organisms in the upper layers of the ocean (14,15). The build-up of sulfides in areas such as the Black Sea is also giving cause for concern (8). 

The enzymology of arsenic biomethylation is complicated because of its many oxidation states, its propensity to react with sulfur compounds, and low concentrations of arsenic compounds in biological specimens. The chemical intermediates and reactions in the metabolism of arsenate are similar in microorganisms and animals. However, in microorganisms, the reactions tend to proceed to methylarsines, whereas in mammalian species the major urinary metabolite is generally dimethylarsinate and only a very small amount of it is reduced further. The arsenate reductase and methylarsonate reductase were thought to play an important role in arsenic biomethylation however, with the exception of arsenate reductase most of the enzymatic experiments involved mammalian systems. 

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