Carbohydrate utilisation

Compare a) the minimum OTR and b) heat evolution rate of a continuous fermentation system based on n-alkanes operating at a dilution rate of 0.2 h 1 and a biomass concentration of 13.5 kg m 3, to a similar system based on carbohydrate. You may need to look back a few pages to get the relevant information concerning carbohydrate utilisation (Section 4.7). 

The range of carbohydrate utilisation differs between different insect cell lines. Glucose, fructose and maltose can be used individually as carbon sources in Sf9 cell cultures [42]. 

Product formation is directly related to carbohydrate utilisation Ethanol... 

Product formation indirectly related to carbohydrate utilisation Citric acid... 

Product formation apparently not associated with carbohydrate utilisation Penicillin... 

Another physiologically important anion is phosphate which is essential for bone formation, for the buffering of biological fluids and as a component of numerous enzyme systems. Intermediary metabolism and, in particular, carbohydrate utilisation are intricately interwoven with the phosphate cycle through the reversible conversion of inorganic phosphate to high energy phosphate in ATP. 

Seeto, G.S., Veivers, P.C., Clements, K.D., and Slaytor, M., Carbohydrate utilisation by microbial symbionts in the marine herbivorous fishes Odax cyanomelas and Crinodous lophodon, J. Comp. Physiol. B, 165, 571, 1996. 

Interest has focussed on four main areas (a) the nature of exogenous carbohydrates utilised by cestodes, (b) the mechanisms by which these carbohydrates are absorbed, (c) the pathways of carbohydrate catabolism and (d) the regulatory control of these pathways. 

Sterry, P. R. McManus, D. P. (1982). Ligula intestinalis biochemical composition, carbohydrate utilisation and oxygen consumption of plerocercoids and adults. Zeitschrift fur Parasitenkunde, 67 87-98. 

Other metabolic effects. In addition to enabling glucose to pass across cell membranes, the transit of amino acids and potassium into the cell is enhanced. Insulin regulates carbohydrate utilisation and energy production. It enhances protein synthesis. It inhibits breakdown of fats (lipolysis). An insulin-deficient diabehc (Type 1) becomes dehydrated due to osmotic diuresis, and is ketotic because fats break down faster than the ketoacid metabolites can be metabolised. 

Physical activity increases carbohydrate utilisation and insulin sensitivity, so that hypoglycaemia is likely if a well-stabilised patient changes suddenly from an inactive existence to a vigorous life. If this is likely to happen the carbohydrate in the diet may be increased and/or the dose of insulin reduced by up to one-third and then readjusted according to need. This is less marked in patients on oral agents. 

Because carbohydrate utilisation is impaired, a lack of insulin leads to the uncontrolled breakdown of lipids and proteins. Large amounts of acetyl CoA are then produced by P oxidation. However, much of the acetyl CoA cannot enter the citric acid cycle, because there is insufficient oxaloacetate for the condensation step. Recall that mammals can synthesize oxaloacetate from pyruvate, a product of glycolysis, but not from acetyl CoA instead, they generate ketone bodies. A striking feature of diabetes is the shift in fuel usage from carbohydrates to fats glucose, more abundant than ever, is spurned. In high concentrations, ketone bodies overwhelm the kidney s capacity to maintain acid—base balance. The untreated diabetic can go into a coma because of a lowered blood-pH level and dehydration. 

In the cold photosynthesis may be limited by a decreased supply of Pi caused by slow sucrose synthesis (1). This is demonstrated by a smaller stimulation of photosynthesis by 2kPa O2 compared to 21kPa O2 with decreasing temperature, and by eventual insensitivity to 2kPa O2 at a temperature dependent on species (2). Carbohydrate accumulates in the cold (3), and feedback inhibition of photosynthesis caused by accumulation of carbohydrate due to low sink demand may occur at low temperatures (4). The rate of export of photosynthate from leaves, can be estimated by monitoring C efflux from l C02 fed leaves (5), and in conjunction with measurements of amounts of carbohydrate, indicates carbohydrate utilisation and sink demand. 

These systems are of interest in connection with the failure of the carbohydrate utilisation mechanism in diabetes, and should have a practical application in clinical treatment. 

Beet juice contains about 80% of fermentable carbohydrates and nitrogenous compounds. To remove these compounds, a yeast fermentation utilising Candida utillis has been suggested (141). By so doiag, a more concentrated form of the dye becomes available. The red dye from beets is sold as beet juice concentrate, as dehydrated beet root, and as a dried powder. 

Studies show that the production of 1kg dry biomass requires 2.0 kg sugar, 0.7 kg oxygen, 0.1 kg ammonia, with the liberation of 12,300 k Joules heat. A typical continuous fermentation operates at a dilution rate (D) = 0.2 h 1, with sugar concentration of 3% (w/v) in the incoming medium. With a fermentor of 50 m3 capacity and 90% utilisation of carbohydrate [ie 0.3% (w/v) sugar in the outgoing medium] what would be ... 

Anaerobic utilisation of carbohydrates is strongly inhibited by the end product ethanol, giving low yield coefficients compared to aerobic utilisation. 

Carbohydrates are relatively cheap, available in large quantities and are readily utilisable source of carbon and energy for most micro-organisms. These considerations are particularly important for those exopolysaccharides produced on a large (bulk chemical) scale. 

Microorganisms under anaerobic growth conditions have the ability to utilise glucose by the Embden-Mereyhof-Parnas pathway.4 Carbohydrates are phosphorylated through the metabolic pathway the end products are two moles of ethanol and carbon dioxide.5... 

Protein concentration can be determined by using method of Bradford,9 which utilises Pierce reagent 23200 (Pierce Chemical Company, Rockford, IL, USA) in combination with an acidic Coomassie Brilliant Blue G-20 solution to absorb at 595 nm when reagent binds to the protein. A 20 mg/1 bovine serum albumin (Pierce Chemical) solution was used as the standard. Starch concentration was measured by the orcinol method4,9-11 using synthetic starch as the reference. A yellow to orange colour is obtained and measured at 420 nm when orcinol reacts with carbohydrates. Absorbance is determined by spectrometry. 

FEURLE, J., JOMAA, H., WILHELM, M GUTSCHE, W.B., HERDRICH, M., Analysis of phosphorylated carbohydrates by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry utilising p-cyclodextrin bonded stationary phase, J. Chromatogr., 1998,803,111-119. 

The plasma concentration of ketone bodies in fed, healthy humans is very low (about 0.1 mmol/L) so that the rate of utilisation is very low. However, it is elevated in several conditions, e.g. starvation, hypoglycaemia, affer physical activity. In starvation in normal adults, it increases to about 3 mmol/L after three days and to 5-6 mmol/L after several more days (Figure 7.24). Nevertheless, it can increase to 3 nunol/L or higher within a few hours of completing a prolonged period of physical activity if food, particularly carbohydrate, is not eaten (known as accelerated starvation ) (Table 7.3). Ketone bodies are particularly important in children, since starvation can quickly result in severe hypoglycaemia. This is due to the fact that the amount of glycogen stored in the liver of a child is... 

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