Zymase

Zymase (a mixture) yeast d-glucose, /-fructose alcohol. CO, and small quantities of glycerol 45-6-5... 

Yeast contains a number of enzymes, more particularly inyertase and zymase. Invertase catalyses the hydrolysis of sucrose to glucose and fructose (cf. the catalysis of this reaction by acids, p. 369). 

It is important to note that this solution does not contain any zymase. 

In order to obtain an extract containing zymase, more complex methods of treatment must be employed. 

In 1878 the term enzyme, Greek for "in yeast," was proposed (8). It was reasoned that chemical compounds capable of catalysis, ie, ptyalin (amylase from sahva), pepsin, and others, should not be called ferments, as this term was already in use for yeast cells and other organisms. However, proof was not given for the actual existence of enzymes. EinaHy, in 1897, it was demonstrated that ceU-free yeast extract ("zymase") could convert glucose into ethanol and carbon dioxide in exactiy the same way as viable yeast cells. It took some time before these experiments and deductions were completely understood and accepted by the scientific community. 

The glucose and fructose formed are then converted into ethanol and carbon dioxide by another enzyme, zymase, which is also present in yeast ... 

Old text books refer to the enzyme zymase as being present in yeast. It is now known that zymase is a complex of fourteen enzymes. 

Ethanol is also produced by the fermentation of sugars such as glucose. The reaction is carried out at about 35°C in the presence of yeast, which contains an enzyme (biological catalyst) called zymase. 

Many chemical changes occurring in living processes are catalyzed by enzymes which are complex protein substances produced by living cells. Enzymes are often present in colloidal state and are very specific in their catalytic action. Zymase obtained from yeast catalyses the fermentation of dextrose but is ineffective in breakdown of cane sugar. 

The chemical course of alcoholic fermentation, which has already been the subject of investigation for more than a century, has been explained chiefly by the work of C. Neuherg and G. Emhden. E. Buchner proved that zymase, the enzyme complex of yeast, can be separated from the living cells. 

Edouard Buchner. Intact yeast cells not required for fermentation, but only the zymases they contain. 

Second, zymase, another enzyme also present in the yeast, converts the glucose and the fractose into ethanol. 

The action of zymase is inhibited once the percentage of alcohol formed exceeds 14 percent. If air gets into fermentation mixture, the ojQTgen of air oxidises ethanol to ethanoic acid which in turn destroys the taste of alcoholic drinks. 

It remains undecided whether the formation of small amounts of glycerol reported by Oppenheimer in the case of zymase extract is due to a ph3rtochemical reduction of trioses. If hexoses are fermented in the presence of trioses with ordinary fresh yeasts which do not attack dihy-droxyacetone and glyceraldehyde, the added trioses are recovered practically unaltered after the disappearance of the hexoses. 

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 ... 

Neumeister, R. (1897) Bemerkungen zu Eduard Buchner s Mittheilungen tiber Zymase . 

BUCHNER, EDUARD (1860—1917). A German chemist who was awarded the Nobel prize for chemistry in 1907. His works included the synthesis of diiodoacelamid through alcoholic fermentation caused by enzymes, as well as the discovery of zymase, die first enzyme to be isolated. He received his Ph.D. at the University of Munich, where he became a lecturer. Later, he taught and performed research at Tubingen, Berlin, and Wiirzburg. 

With the enzyme zymase (of yeasi) yields ethyl alcohol plus carbon dioxide. Specific rotatory power—see glucose below. 

HARDEN. SIR ARTHUR (1865-1940). An English chemist who won the Nobel prize in chemistry in 1929 along with Hans von-Euler C helpin. He discovered fermentation enzy mes and demonstrated the structure of zymase, llis fermentation work proved how inorganic phosphates speeded the process. Bora in England, he received his doctorate in Germany. 

In 1878, the "fragments" identified by Pasteur were named enzymes by the German physiologist Wilhelm Kuhne. In 1897, Eduard Buchner, a German chemist, accidentally discovered that a yeast juice could convert sucrose to ethanol. He was able to show that the sugar was fermented even in the absence of living yeast cells in the mixture, and named the factor responsible for the fermentation of sucrose zymase. In 1907, he received the Nobel Prize in Chemistry. The 40 years of biochemical research that followed yielded the details of the chemical reactions of fermentation. 

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