Carbon sources

Although biochemical tests can be broken down into various groups, the tests are a continuous spectrum and many areas overlap, e.g. the presence or absence of a specific enzyme may determine whether or not a compound can be used as a carbon source. The groups are frequently presented as shown below  

The remainder of this chapter contains examples of each type, and although it is not comprehensive, it contains the tests used to separate the more common species. 

Growth on malonic acid as sole carbon source is used less commonly as a differential test for Enterobacter and Escherichia. Growth is shown by the indicator (Bromothymol Blue) changing to its alkaline colour, Prussian Blue. 

When carrying out these tests it is essential to avoid carry over of medium in the inoculum, and it is best to carry out a second definitive test after obtaining a presumptive positive in the first test. A loopful of organisms from the first positive test (presumptive) is used as inoculum for the second test (confirmatory). 

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A more constrained opportunity for nitrate bioremediation arose at the US-DoE Weldon Spring Site near St. Louis, Missouri. This site had been a uranium and thorium processing faciUty, and treatment of the metal had involved nitric acid. The wastestream, known as raffinate, was discharged to surface inpoundments and neutralized with lime to precipitate the metals. Two pits had nitrate levels that requited treatment before discharge, but heavy rains in 1993 threatened to cause the pits to overflow. Bioremediation by the addition of calcium acetate as a carbon source successfully treated more than 19 million liters of water at a reasonable cost (75). 

At Lake Texcoco, Mexico, bicarbonate is available in the alkaline waters from soda ash [497-19-8] (sodium carbonate) deposits (see Alkali and CHLORINE products). This supply of carbon is adequate for growing Spirulina maxima which tolerates alkaline pH values in the range 9—11 (37,38). Combustion gases have been used to grow this organism, but this carbon source is not available in many regions (49). 

Most of the renewable carbon sources Hsted in Table 8 have carbon contents near this value. When adjusted for moisture and ash contents, it is seen that with the exception of the sludge sample, the carbon contents are slightly higher than that of cellulose, but span a relatively narrow range. 

The proposed mechanism by which chlorinated dioxins and furans form has shifted from one of incomplete destmction of the waste to one of low temperature, downstream formation on fly ash particles (33). Two mechanisms are proposed, a de novo synthesis, in which PCDD and PCDF are formed from organic carbon sources and Cl in the presence of metal catalysts, and a more direct synthesis from chlorinated organic precursors, again involving heterogeneous catalysis. Bench-scale tests suggest that the optimum temperature for PCDD and PCDF formation in the presence of fly ash is roughly 300°C. 

Future Uses. The most recent uses for methanol can be found in the agricultural sector. Test studies are being carried out where methanol is sprayed directly onto crops to improve plant growth. Methanol can be used as a carbon source for the production of single-cell protein (SCP) for use as an animal feed supplement. The process has been commercially demonstrated by ICl at their BiUingham, U.K., faciUty. However, the production of SCP is not commercially practical at this time, in comparison to more conventional protein sources. 

Elemental phosphoms is produced from a phosphoms-rich ore mostiy recovered by strip mining. This ore usually contains fluorapatite, plus some sihca and siUcates. When a carbon source, usually coke, is added to the ore at temperatures greater than 1100°C, the following overall reaction occurs ... 

In operations similar to the E. ashbjii procedures, the closely related fungus Jishbjagossjpii gave similar yields. Thus, a yield of 7.3 g/L was obtained with a lyoptulked culture in a medium containing fat, leather glue, and com extracts (50), and 6.420 g/L with bone or hide fat, alone or in a mixture with other plant or animal fats as the carbon source (51). The yield from immersed cultures ofM. gossjpii was increased to 6.93—7.20 g/L by use of waste fats or technical cod-Hver oil (52). 

Riboflavin is also made by aerobic culturing of Pichiaguilliermondii on a medium containing n-Q g-Q paraffins in a yield of 280.5 mg/L (53). A process employing Pichia yeasts, such as P. miso, P. miso Mogi, or P. mogii, in a medium containing a hydrocarbon as the carbon source, has been patented... 

Further efficient fermentative methods for manufacture of riboflavin have been patented one is culturing C. famata by restricting the carbon source uptake rate, thereby restricting growth in a linear manner by restriction of a micronutrient. By this method, productivity was increased to >0.17 g riboflavin/L/h (63). The other method, using Bacillus subtilis AJ 12644 low in guanosine monophosphate hydrolase activity, yielded cmde riboflavin 0.9 g/ L/3 days, when cultured in a medium including soy protein, salts, and amino acids (64). 

The synthesis which forms the basis of production at Hoffmaim-La Roche (Fig. 5) proceeds via the pyrimidinenitrile [698-29-3] (26) made from malononittile, trimethylorthoformate, ammonia, and acetonitrile (42,43). High pressure catalytic reduction of the nitrile furnishes diamine (16). The overall sequence is short, highly efficient, and generates almost no waste. However, malononittile is a relatively expensive and ha2ardous three-carbon source. 

Although numerous other materials have been proposed as carbon sources for the thiazole ring, all manufacturing of thiamine is beheved to use... 

Cheese whey soHds contain 70—75% lactose, which can serve as the carbon source for lactose fermenting yeasts such as Klujveromjcesfragilis. The total volume produced is considerably smaller than for the other yeasts described. 

One of the most promising substrates for future production of microbial biomass is the ceUulose contained in agricultural residues such as wood pulp, sawdust, feed-lot waste, com stover, rice huUs, nut sheUs, and bagasse, aU of which contain ceUulose as the principal carbon source. CeUulose contents range from 90% in cotton to 15—20% in dicotyledon leaves. Wood residues and grasses contain mixtures of ceUulose, hemiceUulose, and lignin. The major... 

G s-Ph se Synthesis. A gas-phase synthesis route to making fine, pure SiC having controllable properties has been described (78,79). Methane was used as a carbon source if required, and the plasma decomposition of three feedstocks, siUcon tetrachloride [10026-04-7] SiCl, dimethyl dichi orosilane, and methyltrichlorosilane [75-79-6] CH Cl Si, into fine SiC powders was investigated. 

The considerable uses of carbohydrates as carbon sources for various fermentations or the uses of unrefined carbohydrates, flours for example, are also not described here (see Fermentation). 

By beginning with methane, the diamonds formed have only in them. These tiny diamonds may then be used as the carbon source to form large (5 mm) single crystals by growth from molten catalyst metal in a temperature gradient. The resulting nearly pure crystals have outstanding thermal conductivities suitable for special appHcations as windows and heat sinks (24). 

Other non-oxidative procedures have also been used to deaminate aziridines. For example, aziridines react with carbenes to yield ylides which subsequently decompose to the alkene. Dichlorocarbene and ethoxycarbonylcarbene have served as the divalent carbon source. The former gives dichioroisocyanides, e.g. (281), as by-products (72TL3827) and the latter yields imines (72TL4659). This procedure has also been applied to aziridines unsubstituted on the nitrogen atom although the decomposition step, in this case, is not totally stereospecific (72TL3827). 

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