Fermentation and hydration

Fermentation and hydration

Poll

Which process does the picture show?

• hydrolysis

• hydration

• fermentation

Fermentation Method

Yeast is added to sugar solution and left in the warm (about 30⁰C) for several days in the absence of air(anaerobic conditions).Enzymes(biological catalyst) convert sugar into ethanol and carbon dioxide. This process is known as fermentation.

The absence of air and temperature are both important. In the presence of air, enzymes in the yeast produce carbon dioxide and water instead of ethanol. The enzymes are protein catalysts and if the temperature is increased much above 40⁰C the enzyme gets denatured. At lower temperature the reaction is too slow. Somewhere between 30 and 40^oC is the optimum temperature for the reaction.

Fermentation method

Enzymes in the yeast convert glucose into ethanol and carbon dioxide in a large number of steps. The overall equation for that conversion is

C₆H₁₂0₆(aq) → 2C₂H₅OH(aq) + 2C0₂(g)

 glucose            Ethanol             carbon dioxide

Starting materials: glucose (from sugar cane)

 Temperature: 30°c

Catalyst: enzymes in yeast

Other conditions: anaerobic 

Multiple Choice

What are the conditions necessary for fermentation?

• temp 30⁰C, enzymes in yeast, anaerobic

• temp 50⁰C, aerobic

• temp 100^oC, heat

Ethanol by hydration

Ethanol is also made by reacting ethene with steam, a process known as

hydration .

CH₂=CH₂(g) + H₂0(g) → CH₃CH₂0H(g)

Starting materials: ethene and steam

Temperature:300°c

Pressure:60-70 atmospheres

Catalyst: phosphoric acid (H3P04)

Only a small proportion of the ethene reacts. The ethanol produced is

condensed as a liquid and the unreacted ethene is recycled through the

process. 

Poll

State the starting material for the production of ethanol by hydration

• ethane and steam

• ethene and steam

• ethyne and steam

• propene and steam

Open Ended

Which method of making ethanol is used the most?