Carbohydrate fermentation

Some of the economic hurdles and process cost centers of this conventional carbohydrate fermentation process, schematically shown in Eigure 1, are in the complex separation steps which are needed to recover and purify the product from the cmde fermentation broths. Eurthermore, approximately a ton of gypsum, CaSO, by-product is produced and needs to be disposed of for every ton of lactic acid produced by the conventional fermentation and recovery process (30). These factors have made large-scale production by this conventional route economically and ecologically unattractive. 

Acetic 2 Major end product of carbohydrate fermentation by rumen organisms ... 

The presence of unusual carbohydrate fermentation patterns (particularly for lactose), and the ability to use citrate among Enterobacteriaceae has hindered, and sometimes jeopardized, the identification of pathogenic strains including Salmonella typhi. 

Due to fermentation of hitherto undigested carbohydrates by the cecal and colonic bacteria (the large bowel contains concentrations of bacteria of up to 10lo-1012 bacteria/ mL), the pH in the proximal colon is usually lower than that of the ileum. This is reflected in the composition of SCoF, which is essentially an acetate buffer. The use of acetate is appropriate as it is known that the products of carbohydrate fermentation include very short chain acids (acetate, propionate, and butyrate are typical). 

Armstrong WG (1960b) Reaction in vitro of sound dentine with glucose, glucosamine and carbohydrate fermentation and degradation products. Arch Oral Biol 5, 179-189. 

Cockcroft A. E., M. McDermott, J. H. Edwards, and P. McCarthy. Grain exposure— symptoms and lung function. Eur JRespirDis 1983 64(3) 189-196. Lupton J. R., J. L. Morin, and M. C. Robinson. Barley bran flour accelerates gastrointestinal transit time. J Am Diet Assoc 1993 93(8) 881-885. Thorbum A., J. Muir], and]. Proietto. Carbohydrate fermentation decreases hepatic glucose output in healthy subjects. Metabolism 1993 42(6) 780-785. 

Fermentation is the anaerobic decomposition of organic compounds, basically carbohydrate, into alcohols by the action of bacterial enzymes. Ethanol is the desired product of carbohydrate fermentation, but other alcohols, acids, ketones, and aldehydes can form as by-products. One common example of ethanol production from biomass is the fermentation of com. For illustration, this process will be summarized. 

There are many methods for the prepn of acet of which the dry distn of Ca acetate was the most common until, a few years after WWI, the carbohydrate fermentation method of C.Weizmann was introduced (Refs 31 48). 

Ueno, Y., Haruta, S., Ishii, M., and Igarashi, Y. (2001). Changes in product formation and bacterial community by dilution rate on carbohydrate fermentation by methanogenic microflora in continuous flow stirred tank reactor. Appl. Microbiol. Biotechnol. 57, 65-73. 

Microorganisms are also capable of separating optical isomers. In the case of sodium glutamate, where it is necessary to start from levo-glutamic acid to obtain the desired flavor, and where synthesis produces only a racemic blend, it was a particular yeast called Micrococcus glutamicus that led to the required isomer through carbohydrate fermentation. 

On the other hand, organics may be removed fi"om aqueous solutions by applying a high silica membrane of a suitable pore size. An application might be the continuous removal of ethanol by e.g. a Silicalite-1 based membrane from carbohydrate fermentation liquids. The Microorganisms used are deactivated at an alcohol content > 12%. By continuous removal of the alcohol produced its concentration may be kept at a level below 12% enabling a higher final conversion of the carbohydrate feed. 

As with M. ruminantium, Methanobacterium strain MOH can utilize neither peptides nor amino acids as a nitrogen source replacing NH4 (Figures 5 and 7). NH4 utilization is essentially the same (Figure 8) when NH4 is the nitrogen source or when rumen fluid, amino acids, yeast extract, and Trypticase are present in the medium as complex sources of nitrogen that would be utilized in place of NH4 by most heterotrophic bacteria other than some rumen carbohydrate-fermenting anaerobes (11). 

The reason for the inefiiciency of these bacteria in utilizing amino acids is not definitely known however, it seems probable, as is the case with some of the carbohydrate-fermenting rumen bacteria (8, 33), that these materials are not transported effectively into the cell. It seems probable that, in their adaptation to the natural habitat, their abilities to utihze proteins and amino acids were of little survival value and were lost. It is well known that amino acids are present in very small amounts in extracellular fiuid of rumen contents while relatively high concentrations of ammonia and acetate and other volatile acids including 2-methylbutyrate are present (8). A similar condition probably exists in sludge although the volatile acids are usually present in lower concentration than in the rumen. 

The results of the analysis are illustrated in Figure 3. Protein and carbohydrate fermentation occur extensively at 0c values of less than one day, while fermentation of the fatty acids formed occurs only at 0c values... 

FlGURt Pathwaj-s of gas formation due to fiber fermeritation in the intestines. Some of the hydrogen gas produced by the carbohydrate fermenters may be released unchanged from the host. Methane production i.s variable in humans. About one-third of adult humans are methane producers. Some of the Hj may be used by methanogens for CJ f production. 

Pomare, E. W., Branch, W. J., and Cummings, J. H. (1985). Carbohydrate fermentation in the human colon and its relation to acetate concentrations in venous blood. /. Clin. Invest. 75,1448-1454. 

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