Question

Yeast is used in the production of
(a) Sugar
(b) Alcohol
(c) Hydrochloric acid
(d) Oxygen

Answer 1

Yeast is a unicellular fungus that reproduces asexually by budding or division. Yeast depends on oxygen and food such as sugar to multiply and grow. As the byproduct after feeding on sugar, they produce chemicals, which are of major commercial importance.

Complete step by step answer:
Yeast is used in the production of Alcohol via a process known as fermentation. The genus Saccharomyces is of major importance in the food and beverage industry. Most yeasts require an abundance of oxygen for their growth and multiplication. They also require a basic substrate such as sugar ($C_{6}H_{12}O_{6}$) . Some yeast can convert sugars to alcohol and carbon dioxide in the absence of oxygen but require oxygen for growth. They produce ethyl alcohol ($C_{2}H_{5}OH$) and carbon dioxide ($CO_{2}$) from simple sugars, glucose, and fructose.
$C_{6}H_{12}O_{6} \overrightarrow{Yeast} 2C_{2}H_{5}OH+2CO_{2}$
- The favorable temperature range for the growth of yeast is from $0^{\circ}C$ to $50^{\circ}C$, with an optimum temperature range of $20^{\circ}C$ to $30^{\circ}C$.
- Yeasts are acid- tolerant and cause spoilage of acidic foods and can grow in a pH range of 4 to 4.5.
- By controlling the amount of oxygen supply, their growth and multiplication can be checked.
- In terms of the water requirements, yeasts are intermediate between bacteria and molds and require a relative humidity of 88% for optimum growth.
- Yeasts are highly tolerant of high concentrations of sugar and grow well in solutions containing 40% sugar.
So, the correct answer is, ‘(b) Alcohol.’

Note: In the case of excess oxygen (and in the presence of acetobacter bacteria) the alcohol can be oxidized to form acetic acid. Formation of acetic acid is undesirable if the end product is fruit alcohol, but the acetic acid is employed for the production of fruit vinegar.