Hydrogen formation microbial

However, hydrogen production from acetate oxidation, as aimed for in an MEC, is thermodynamically not feasible. Indicated by the equilibrium potentials of the individual half reactions at microbial conditions (pH 7, acetate 1 M, 1 bar), the electromotive force (emf) (= cathode potential - anode potential) of this reaction is -0.14 V, which means that additional electrical energy is required to support electrolytic hydrogen formation (Fig. 2). This is provided by applying a circuit voltage that is... 

The anaerobic microbial processes responsible for the formation of odor-causing substances produce inorganic gases and VOCs. The malodorous inorganic gases are primarily ammonia (NH3) and hydrogen sulfide (H2S). 

Functionally and mechanistically reminiscent of the pyruvate lyases, the 2-deoxy-D-ribose 5-phosphate (121) aldolase (RibA EC 4.1.2.4) [363] is involved in the deoxynucleotide metabolism where it catalyzes the addition of acetaldehyde (122) to D-glyceraldehyde 3-phosphate (12) via the transient formation of a lysine Schiff base intermediate (class I). Hence, it is a unique aldolase in that it uses two aldehydic substrates both as the aldol donor and acceptor components. RibA enzymes from several microbial and animal sources have been purified [363-365], and those from Lactobacillus plantarum and E. coli could be induced to crystallization [365-367]. In addition, the E. coli RibA has been cloned [368] and overexpressed. It has a usefully high specific activity [369] of 58 Umg-1 and high affinity for acetaldehyde as the natural aldol donor component (Km = 1.7 mM) [370]. The equilibrium constant for the formation of 121 of 2 x 10M does not strongly favor synthesis. Interestingly, the enzyme s relaxed acceptor specificity allows for substitution of both cosubstrates propional-dehyde 111, acetone 123, or fluoroacetone 124 can replace 122 as the donor [370,371], and a number of aldehydes up to a chain length of 4 non-hydrogen atoms are tolerated as the acceptor moiety (Table 6). 

In order to avoid chemical compounds at all, it is also possible to apply a high voltage to kill microbes on surfaces. It was found that a direct current kills E. coli cells, probably by heat or by hydrogen peroxide formation [84], Microbial cells can be effectively killed by using pulsed electric fields (PEF), probably by frequently disturbing the cell membrane potential [85], PEF that was found to lower microbial cell numbers in food and drinks was also shown to effectively kill E. coli and Listeria innocua cells attached to polystyrene beads [86], This demonstrates the potential of applying this purely physical method to surfaces as well. 

Sulfate reduction is the terminal microbial process in anaerobic sediments, when S042- is not limiting, leading to the formation hydrogen sulfide (H2S). This process has been shown to be particularly important in the cycling of S and C chemistry of highly productive shallow-water subtidal and salt marsh environments. 

Sulfate reduction the terminal microbial process in anaerobic sediments, when SO42-is not limiting, leading to the formation of hydrogen sulfide (H2S). 

Microbially influenced corrosion occurs in soil environment. The sulfate-reducing bacteria (SRB) reduce sulfate to sulfide and as a result iron sulfide is formed due to corrosion. The iron sulfide deposit on the steel surface and the steel form a galvanic couple, which is substained by the removal of electrons in the form of cathodic hydrogen, followed by the further formation of more iron sulfide.19,20... 

Conversion of the Microbially Produced Preadhesive to an Adhesive Protein. The polyphenolic protein purified from yeast adheres to a wide variety of surfaces including glass and plastic. The adherence probably results from the presence of many polar residues capable of hydrogen bonding and lysine residues that can form ionic interactions. However, this protein does not generate water-resistant bonds to surfaces nor does it have cohesive strength. For those purposes, it is necessary to convert at least a portion of the tyrosine residues to dopa and permit crosslink formation to occur after surface adhesion is achieved. That is, it is necessary to mimic the natural mussel process in which the dopa form of the polyphenolic protein is applied and then rapidly... 

The usual jarosites formed in these situations are hydronium, potassium or ammonium forms in which A is hydrogen, potassium or ammonium ion. In leaching situations, jarosite formation can strip out essential microbial nutrients such as potassium and ammonium ions (Duncan and Walden, 1972 L.A.V. Sulligoi, 1972, personal communication). 

Sulfur is treated in Chapter 13 and discussed only briefly here. The dominant reaction in the sedimentary sulfur cycle is microbial sulfate reduction. This gives rise to the formation of hydrogen sulfide which, by precipitating iron as "black unstable sulfide", will give the reduced sediment its characteristic blackish color ... 

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