Fermentation glucose-to-ethanol

Glucose-to-ethanol fermentation is to be carried out in a batch reactor using an organism such as Saccharomyces cerevisiae. Plot the concentrations of cells, substrate, and product and growth rates as functions of time. The initial ceil concentration is 1.0 g/dm and the substrate (glucose) concentration is 250 g/dm. ... 

For the glucose-to-ethanol fermentation, typical inhibition parameters are n = 0.5 and... 

Biochemistry resulted from the early elucidation of the pathway of enzymatic conversion of glucose to ethanol by yeasts and its relation to carbohydrate metaboHsm in animals. The word enzyme means "in yeast," and the earfler word ferment has an obvious connection. Partly because of the importance of wine and related products and partly because yeasts are relatively easily studied, yeasts and fermentation were important in early scientific development and stiU figure widely in studies of biochemical mechanisms, genetic control, cell characteristics, etc. Fermentation yeast was the first eukaryote to have its genome elucidated. 

Example 12.7 Develop a model for the anaerobic batch fermentation of glucose to ethanol and coproduct CO2 using Saccharomyces cerevisiae. The starting mixture contains 10% glucose. The inoculum is 0.0005 w/w. Product inhibition stops cell growth at 14% ethanol. Assume ka = 0 but include the cannibalization of cellular material beginning when the substrate is completely consumed. 

Gilson, C. D., and Thomas, A., A Novel Fluidised Bed Bioreactor for Fermentation of Glucose to Ethanol Using Alginate Immobilised Yeast, Biotechnol. Tech., 7 397 (1993)... 

Similar work was performed by Shaw et al.3 in 1999 when they used FT-Raman, equipped with a charge coupled device (CCD) detector (for rapid measurements) as an on-line monitor for the yeast biotransformation of glucose to ethanol. An ATR (attenuated total reflectance) cell was used to interface the instrument to the fermentation tank. An Nd YAG laser (1064 nm) was used to lower fluorescence interference and a holographic notch filter was employed to reduce Rayleigh scatter interference. Various chemometric approaches were explored and are explained in detail in their paper. The solution was pumped continuously through a bypass, used as a window in which measurements were taken. 

Prior to fermentation, the wort is then cooled to temperatures below 85°F (30°C), and the pH is adjusted to about 5. Yeast such as Saccharomyces cerevisiae, Saccharomyces carlsbergensis or Candida brassicae are added and fermentation proceeds for 2 to 3 days under batch processing conditions. Yeast produces the enzymes maltase, zymase, and invertase. Maltase converts maltose to glucose. Zymase converts glucose to ethanol. Invertase converts any sucrose present to fermentable sugar. The following equations illustrate the enzymatic conversion of starch to ethanol ... 

Conversions of primary feedstocks by fermentations (such as glucose to ethanol) are not included in this book. However, fermentations are usually required to produce the enzymes or cells in the first place, and therefore chapter 5 includes a review of this type of fermentation. Chapter 5 also covers the other aspects of biocatalyst production, except immobilization and protein and genetic engineering, which are treated in chapter 6 and 7, respectively. 

Probtom 17.52 In the biochemical conversion of the sugar glucose to ethanol (alcoholic fermentation) a key step is... 

Yeast and other microorganisms ferment glucose to ethanol and C02, rather than to lactate. Glucose is converted to pyruvate by glycolysis, and the pyruvate is converted to ethanol and C02 in a two-step process ... 

Deep-sea explorations have revealed many species of marine life at great ocean depths, where the oxygen concentration is near zero. For example, the primitive coelacanth, a large fish recovered from depths of 4,000 m or more off the coast of South Africa, has an essentially anaerobic metabolism in virtually all its tissues. It converts carbohydrates to lactate and other products, most of which must be excreted. Some marine vertebrates ferment glucose to ethanol and C02 in order to generate ATP. 

Requirement for Phosphate in Ethanol Fermentation In 1906 Harden and Young, in a series of classic studies on the fermentation of glucose to ethanol and C02 by extracts of brewer s yeast, made the following observations. (1) Inorganic phosphate was essential to fermentation when the supply of phosphate was exhausted, fermentation ceased before all the glucose was used. (2) During fermentation under these conditions, ethanol, C02, and a hexose bisphosphate... 

The values of AGox (Table 6-4) not only give an immediate indication of the relative amounts of energy available from oxidation of substrate with NAD+ but also are very convenient in evaluating AG for fermentation reactions. For example, consider the fermentation of glucose to ethanol (Eq. 6-60) ... 

The Gibbs energy change AG (pH 7) for fermentation of glucose to ethanol and C02 can be written immediately from the data of Table 6-4 (Eq. 6-61). 

Enterobacteria, including E. coli, convert glucose to ethanol and acetic acid and either formic acid or C02 and H2 derived from it. The stoichiometry is variable but the fermentation can be described in an idealized form as follows ... 

A yeast culture is fermenting glucose to ethanol. To ensure that the C02 released during fermentation is radiolabeled, what carbon(s) of glucose must be labeled with l4C ... 

Cellulosic Materials. Over 900 x 106 metric tons of carbohydrate-containing cellulosic wastes are generated annually. The technology for converting this material into ethanol is available, but the stoichiometry of the process is disadvantageous. Even if each step in the process of the conversion of cellulose to ethanol proceeded with 100% yields, almost two-thirds of the mass would disappear during the sequence, most of it as carbon dioxide in the fermentation of glucose to ethanol. This amount of carbon dioxide leads to a disposal problem rather than to a raw material credit (209). 

The fermentability of the solution gave good results. The achieved ethanol yields were about 90%, slightly above those obtained with a reference sugar solution, showing that baker s yeast could adapt to the pretreated liquor and ferment the glucose to ethanol without problems. 

We explored the influence of dilution rate and pH in continuous cultures of Clostridium acetobutylicum. A 200-mL fibrous bed bioreactor was used to produce high cell density and butyrate concentrations at pH 5.4 and 35°C. By feeding glucose and butyrate as a cosubstrate, the fermentation was maintained in the solventogenesis phase, and the optimal butanol productivity of 4.6 g/(L h) and a yield of 0.42 g/g were obtained at a dilution rate of 0.9 h1 and pH 4.3. Compared to the conventional acetone-butanol-ethanol fermentation, the new fermentation process greatly improved butanol yield, making butanol production from corn an attractive alternative to ethanol fermentation. 

Requirement for Phosphate in Ethanol Fermentation In 1906 Harden and Young, in a series of classic studies on the fermentation of glucose to ethanol and C02 by extracts of brewer s yeast, made... 

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