Carbon assimilation tests

Wickerham, L.J. and Bnrton, K.A. (1948) Carbon assimilation tests for the classification of yeasts. Journal of Bacteriology, 56 363-371. 

Assimilation tests for carbon compounds use yeast nitrogen base (YNB) without carbon sources, and the assimilation test for nitrogen compounds use yeast carbon base (YCB) without assimilable nitrogen sources. For the tests described, YNB without amine acids and ammonium sulfate is used (Anonymous, 1984). Carbon sources normally examined include a number of pentoses, hexoses, disaccharides, trisaccharides, polysaccharides, alcohols, organic acids, and glycosides as specified by Yarrow (1998). Nitrogen sources commonly tested include nitrate, nitrite, ethyl-amine hydrochloride, cada-verine dihydrochloride, L-lysine, imidazole, glucosamine, creatine, and creatinine. When nitrite is used as a test compound, it is necessary to adjust the pH of the medium to 6.5 because toxic nitrous acid is formed at pH <6.0. 

In comparing transpiration ratio, it is assumed that A is constant among the test species. Actually, the slope of the graph T P versus A gives a better indication of water use efficiency in terms of carbon assimilated. 

Data on the radiocarbon tracer detected in a mixture of plant species from the terrarium is shown in Table 9. These results confirm that polymer fragments produced by the photo-degradation of certain plastic molecules are indeed attacked and metabolized by soil micro-organisms, and are assimilated into the natural carbon cycle. Because radiocarbon assay of the CO2 produced by plant and animal respiration does not reflect the total carbon assimilated in the bodies of plants and microorganisms, this procedure will tend to underestimate the actual rate of biodegradation of the plastic fragments in a natural environment. In these tests, almost half of the carbon metabolized was found in the bodies of the growing plants. 

Once the model was complete, it was adjusted to a steady state condition and tested using historic carbon isotope data from the atmosphere, oceans and polar ice. Several important parameters were calculated and chosen at this stage. Sensitivity analysis indicated that results dispersal of the missing carbon - were significantly influenced by the size of the vegetation carbon pool, its assimilation rate, the concentration of preindustrial atmospheric carbon used, and the CO2 fertilization factor. The model was also sensitive to several factors related to fluxes between ocean reservoirs. 

As shown in Fig. 6B, a two-phase pattern occurred for the substrate uptake. It can be observed that during the exponential growth phase, sucrose assimilation by the bacteria was small, corresponding to about 20% of the initial amount introduced into the medium. However, after a 40-h process corresponding to the end of the growth phase, there was a rise in the substrate uptake, suggesting that the carbon source was directed to biosurfactant production, for the conditions tested. It should be emphasized that the fermentative process, when the medium was supplemented with microsalts and EDTA (Fig. 6A), generated a different substrate kinetics in comparison with that obtained for the nonsupplemented medium (Fig. 6B). 

Although carbon is chiefly assimilated by phytoplankton as C02, a significant amount of bicarbonate-C is removed from seawater by those producing tests of calcium carbonate ... 

It has been shown that more severe conditions mainly increase the carbon of the second zone, which corresponds to the one on the acidic function. It can be considered that the effects of a higher severity may be assimilated with larger periods of operating time, as by DTA we have found the same kind of coke from accelerated deactivation tests and long time operation under normal conditions. Our results are consistent with Gates et al. 

Photosynthesis is the process that provides energy to all anabolic and catabolic processes in ecosystems. The rate at which plants assimilate CO2 in the field may be quite different from optimal conditions in the test tube or in growth cabinets. The rate depends on the environmental conditions of the habitat which determine to what extent the genetic capability of a plant can actually be used for photosynthesis. The main factor restricting photosynthesis in the field is the availability of light. But, other factors my become just as rate 1imitating, such as atmospheric carbon dioxide concentration, air humidity and temperature, and water or nutrient supply from the soil. Time is an additional important factor which influences the carbon balance via plant age but also by deterimining the dose of stress. 

According to ASTM requirements 90% of the carbon of the test materials must be assimilated by the compost microorganisms as dociunented by measuring CO2 production, within a six month period, extendable to one year if radiolabelled carbon is used. Moreover, disintegration of the film or article of the use thickness such that less than 10% of the material remains on a 10 mesh screen after sieving must be proved. Safety of compost must be proved by testing phyto- or ecotoxicity using methods listed in the Standard. 

Conversion of 90%+ of the test material s carbon to CO2 via microbial assimilation of the test polymer material in powder, film or granule form in 180 days or less -a laboratory-scale test method, as described in the previous section. 

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