Anaerobic fermentation products

Volatile fatty acid homologs higher than acetic acid have not been found as natural products of woody plants, although such acids and their esters are important components that contribute to the organoleptic properties of fruits. Nevertheless, propionic, butyric, valeric, and caproic acids occur in wetwood, in addition to elevated levels of acetic acid, as anaerobic fermentation products of starch (34, 36, 37, 43). For example, the concentration of acetic, propionic, and butyric acids of 0 to 3 mM in normal sapwood of white fir increases to as much as 38, 55, and 23 mM, respectively, in the wetwood of some fir species (38). The volatile fatty acids in gum turpentine and in the low wine (the aqueous phase of turpentine distillation) and turpentine tailings (24) also are likely the product of anaerobic fermentation. However, it should be noted that the oleoresin turpentine from Pinus sabiniana consists primarily of -heptane (22), and the turpentine from R jeffreyi contains a significant proportion of -heptane (22) and smaller amounts of A2-pentane, nonane, and undecane (39). The -heptane is derived not through the mevalonate pathway but rather by decarboxylation of octanoic acid (32). Presumably, the other hydrocarbons are also formed by decarboxylation. 

Product formation stoichiometry can be used to estimate the upper bounds for product yields in processes. A relatively simple example is the anaerobic fermentation of glucose by yeast. Here, carbon dioxide and ethanol are the only products. Modification of (E -3.9) then becomes ... 

The term three-phase fluidization, in this chapter, is taken as a system consisting of a gas, liquid, and solid phase, wherein the solid phase is in a non-stationary state, and includes three-phase slurry bubble columns, three-phase fluidized beds, and three-phase flotation columns, but excludes three-phase fixed bed systems. The individual phases in three-phase fluidization systems can be reactants, products, catalysts, or inert. For example, in the hydrotreating of light gas oils, the solid phase is catalyst, and the liquid and gas phases are either reactants or products in the bleaching of paper pulp, the solid phase is both reactant and product, and the gas phase is a reactant while the liquid phase is inert in anaerobic fermentation, the gas phase results from the biological activity, the liquid phase is product, and the solid is either a biological carrier or the microorganism itself. 

There is considerable interest in the role of formic acid and other volatile fatty acids in the early diagnosis of organic matter in lacustrine and marine sediments. Formic acid is an important fermentation product or substrate for many aerobic and anaerobic bacteria and for some yeasts, hi the atmosphere, formic acid is an important product in the photochemical oxidation of organic matter. 

Han, S.-K., Shin, H.-S. 2004. Biohydrogen production by anaerobic fermentation of food waste. Int J Hydrogen Energy 29 569-577. 

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