Hydrogen production nutrients

Previous experiments showed that C. saccharolyticus did not depend on nutrients for hydrogen production from paper sludge hydrolysate (15). 

Lin, C. Y., and Lay, C. H. 2005. A nutrient formulation for fermentative hydrogen production using anaerobic sewage sludge microflora. Int. J. Hydrogen Energy, 30, 285-292. 

Turcot, J., BisaiUon, A., HaUenbeck, P.C., 2008. Hydrogen production by continuous cultures of Escherchia coli under different nutrient regimes. International Journal of Hydrogen Energy 33, 1465-1470. 

Onwudili, J.A., et al., 2013. Catalytic hydrothermal gasihcation of algae for hydrogen production composition of reaction products and potential for nutrient recycling. Bioresource Technology 127 (0), 72—80. 

Arsenic is another element with different bioavailabiUty in its different redox states. Arsenic is not known to be an essential nutrient for eukaryotes, but arsenate (As(V)) and arsenite (As(III)) are toxic, with the latter being rather more so, at least to mammals. Nevertheless, some microorganisms grow at the expense of reducing arsenate to arsenite (81), while others are able to reduce these species to more reduced forms. In this case it is known that the element can be immobilized as an insoluble polymetallic sulfide by sulfate reducing bacteria, presumably adventitiously due to the production of hydrogen sulfide (82). Indeed many contaminant metal and metalloid ions can be immobilized as metal sulfides by sulfate reducing bacteria. 

There is a general understanding of the reasons why nutrients are critical to the productive capacity of biological systems. The dry biomass of plants and animals comprises some 20 elements, the predominant atoms being those of carbon, hydrogen, oxygen, and nitrogen. Moreover, ideally they are required in fairly... 

Organisms also evolved powerful detoxifying mechanisms that remove toxic materials or convert them to non-toxic forms or nutrients. Examples of alterations to non-toxic forms are the conversions of hydrogen sulfide to sulfate and nitrite to nitrate. The prime example of development of the ability to use a toxic substance is the evolution of aerobic metabolism, which converted a serious and widespread toxin, oxygen, into a major resource. This development, as we have seen, greatly increased the productivity of the biosphere and generated the oxygen-rich atmosphere of today s Earth. 

The pathway of the metabolic process converting the original nutrients, which are of rather complex composition, to the simple end products of COj and HjO is long and complicated and consists of a large number of intermediate steps. Many of them are associated with electron and proton (or hydrogen-atom) transfer from the reduced species of one redox system to the oxidized species of another redox system. These steps as a rule occur, not homogeneously (in the cytoplasm or intercellular solution) but at the surfaces of special protein molecules, the enzymes, which are built into the intracellular membranes. Enzymes function as specific catalysts for given steps. 

Harrison, Tarr and Hibbert96 investigated the production of levan from sucrose by the action of Bacillus subtilis Cohn and B. mesentericus Trevisan. Nutrient solutions containing 10% carbohydrate, 0.1% peptone, 0.2% disodium hydrogen phosphate and 0.5% potassium chloride were incubated at 37° for six days. Levan formation occurred only with sucrose and raffinose, and not with melezitose, lactose, maltose, D-xylose, D-glucose or D-fructose. It was therefore suggested that only those carbohydrates with a terminal D-fructofuranose residue were satisfactory substrates for levan formation. 

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