Glucose fermentation processes

Bekatorou A., Koutinas A.A., Kaliafas A. and Kanellaki M. Freeze-dried Saccharomyces cerevisiae cells immobilized on gluten pellets for glucose fermentation. Process Biochemistry 36 (6) (2001) 549-557. 

Xyhtol (Fig. Ig) is found in the primrose (38) and in minor quantity in mushrooms (39). It can be obtained from glucose in 11.6% overall yield by a sequential fermentation process through D-arabinitol and D-xylulose (28). 

Grain that is usable as food or feed is an expensive substrate for this fermentation process. A cheaper substrate might be some source of cellulose such as wood or agricultural waste. This, however, requires hydrolysis of cellulose to yield glucose. Such a process was used in Germany during World War II to produce yeast as a protein substitute. Another process for the hydrolysis of wood, developed by the U.S. Forest Products Laboratory, Madison, Wisconsin, uses mineral acid as a catalyst. This hydrolysis industry is very large in the former Soviet Union but it is not commercial elsewhere. 

The long fermenting process converts several glucosides into glucose, vanillin, and other complex aromatic flavors. The vanilla beans can be further processed by extracting soluble compounds in ethanol and water mixtures, resulting in vanilla extract. 

Traditional fermentation processes can only make use of glucose, leaving other sugars present, notably xylose, untouched. This both increases the waste element and lowers the competitiveness of the process compared to petrochemical-based ethanol. 

The distinctive aroma of ammonia is often apparent in bakeries but not in the final product. Bakers yeast performs its leavening function by fermenting such sugars as glucose, fructose, maltose, and sucrose. The principal products of the fermentation process are carbon dioxide gas and ethanol, an important component of the aroma of freshly baked bread. The fermentation of the sugar, glucose—an example of a decomposition reaction — is given by the equation in Fig. 5.19.1. 

In an fermentation process of a solution containing sucrose, the enzyme in-vertase, present in yeast, acts as a catalyst to convert sucrose into a 1 1 mixture of glucose and fructose. Thus, sucrose is a disaccharide that hydrolyzes in the presence of certain bacteria to yield glucose and fructose. The ether linkage in sucrose is broken to yield two alcohols ... 

Cetus A four-stage fermentation process for making propylene oxide from glucose. The product is obtained as a dilute aqueous solution. Developed by Cetus Corporation in the 1970s but not commercialized. 

The compactness and complexity of (ligno)cellulose makes it much more difficult to attack by enzymes with respect to starch. Therefore, the cost of bioethanol production is higher [23], To be cost competitive with grain-derived ethanol, the enzymes used for biomass hydrolysis must become more efficient and far less expensive. In addition, the presence of non-glucose sugars in the feedstock complicates the fermentation process, because conversion of pentose sugars into ethanol is less efficient than conversion of the hexose sugars. 

Biosensors are analytical devices that incorporate a biological component and a transducer. These must be in close proximity with one another and preferably in intimate contact, i.e. the biological component immobilized on to the transducer. Such devices are available in disposable forms, e.g. for measurement of blood glucose in diabetic patients, evaluation of the freshness of uncooked meat. Other designs are suitable for continuous use, e.g. on-line monitoring of fermentation processes, the detection of toxic substances. 

Kansiz et al. has published a paper wherein they used MIR and sequential injections to monitor an acetone-butanol fermentation process.17 In this work, acetone, acetate, n-butanol, butyrate, and glucose were analyzed automatically, using computer-controlled sampling techniques. In this case, gas chromatography was the reference method. The SEPs for the components were acetone, 0.077 acetate, 0.063 butyrate, 0.058 -butanol, 0.301 and glucose, 0.493 g/1. The authors state that the precision and accuracy of the MIR methods were as good as the reference method. 

In another fermentation process, Mosheky et al.18 reacted Saccharomyces cerevisiae with sugars and followed the progress of the fermentation with MIR-ATR. Two PLS models were used one for sucrose, fructose, and glucose and one for the ethanol. The authors did not specify SEPs for the experiment, but showed correlation coefficients of better than 0.998 for all analytes. 

Large amounts of D-glucose—in crude form as obtainable from corn, potatoes, or molasses by acid hydrolysis—enter industrial fermentation processes in the... 

A biotransformation, as defined by Straathof et al., ° is a process that describes a reaction or a set of simultaneous reactions in which a pre-formed precursor molecule is converted using enzymes and/or whole cells, or combinations thereof, either free or immobilised . Fermentation processes, with de novo product formation from a carbon and energy source, such as glucose via primary metabolism, are outside the scope of this chapter and book unless employed in conjunction with a biotransformation. 

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