This set of Fermentation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Brewing Yeast – Cell Wall and Flocculation”.
1. What is the percentage of glucans found in the cell wall of yeast?
a) 25 – 30 %
b) 30 – 60 %
c) 50 – 70 %
d) 40 – 50 %
View Answer
Explanation: Glucans account for 30 – 60 % in the cell wall of yeast. It is the major polymers found in the cell wall of yeast. They cover the entire cell in the form of the microfibrillar net and are restricted to the inner layer of the wall.
2. Who described glucans into three classes?
a) Cabib
b) Kollar
c) Fleet
d) Ballou
View Answer
Explanation: Fleet in 1991 described glucans into three classes: alkaline insoluble- acetic acid insoluble β-(1,3), alkali-soluble β-(1,3), and highly branched β-(1,6). Alkali-soluble accounts for 20% of the cell wall, alkaline insoluble- acetic acid insoluble accounts for 30% of the cell wall and highly branched accounts for only 5% of the cell wall.
3. The outer layer of the cell wall is composed of ___________
a) Mannoprotein
b) Lysosome
c) Glucans
d) Chitin
View Answer
Explanation: The outer layer of the cell wall is composed of mannoprotein. It is a glycoprotein that accounts for 25 – 50 % of the cell wall. Mannoproteins are essential in the cell wall for the survival of the cell. They play an important role as antigenic determinants.
4. Chitin is present in the cell wall of ___________
a) Bacteria
b) Protozoa
c) Fungi
d) Viruses
View Answer
Explanation: Chitin is found in the cell wall of fungi. It is also found in the exoskeleton of crustaceans and insects. It is a linear polymer of β-(1,4) linked with N-acetylglucosamine. It is an important polysaccharide present in the cell wall of yeasts.
5. Which of the following is used to break the cell wall of fungi?
a) Lysozyme
b) Chitinase
c) Protease
d) Mannose
View Answer
Explanation: Chitinase is used to break the cell wall of fungi as chitin is a polysaccharide present in the cell wall of fungi and yeasts. They break the glycosidic bond in chitin resulting in the breakdown of the cell wall.
6. Which of the following separates the suspended particles from liquids?
a) Acid washing
b) Flocculation
c) Fining
d) Fermenting
View Answer
Explanation: Fining is a process that separates suspended particles from liquids. The fining agents are added to the wine or beer to create an adsorbent with the suspended particles, leading to the precipitation of particles out of the wine or beer.
7. What do you mean by trub?
a) Carbohydrates
b) Lipids
c) Hop
d) The complex of carbohydrates, lipids, hop, polyphenols
View Answer
Explanation: Trub is the complex of carbohydrates, insoluble proteins, lipids, polyphenols, and hop substances. It is a miscellany of substances. The complexity of trub depends on the composition of wort. The more turbid the wort, the more trub it contains.
8. Who proposed the adhesins?
a) Miki
b) Stratford
c) Eddy
d) Rudin
View Answer
Explanation: Miki et al. in 1982 proposed the involvement of lectin-like proteins or ‘adhesins’ in flocculation. The interaction of lectin-like proteins with the mannose receptors is accepted as being at the heart of flocculation. Adhesins are present on the flocculent cell surfaces.
9. Which of the following is a major candidate of flocculation receptor?
a) Chitin
b) Mannose
c) Lysosome
d) Glucans
View Answer
Explanation: Mannose is the major candidate of the flocculation receptor as it is the major component of the yeast cell wall. Miki et al. in 1982 showed the inhibition of the flocculation process by a plant lectin (Concanavilin A) which selectively binds to α-mannan.
10. The product of FLO 1 gene is involved in ___________
a) Fining
b) Sedimentation
c) Flocculation
d) Agglutination
View Answer
Explanation: The product of FLO 1 gene is a cell wall protein that is involved in flocculation. The flocculation is strongly correlated with the amount of FLO 1 protein that is expressed.
11. Which of the following is a key determinant of cell hydrophobicity?
a) Sulfur
b) Potassium
c) Sodium
d) Phosphate
View Answer
Explanation: Phosphate is the key determinant of cell hydrophobicity which appears in the outer layer of the cell wall. Hydrophobicity is associated with low phosphate and vice and versa. It is also related to the age of the cell, and the number of bud scars.
12. Zeta potential is the measure of __________
a) Flocculation
b) Surface charge
c) Agglutination
d) Fermentation product
View Answer
Explanation: Zeta potential is the measure of surface charge which is primarily determined by phosphate found in the cell wall mannoproteins and the pH of the surrounding medium. A curvilinear relationship is observed between increasing phosphate concentration and negative zeta potential.
13. Proteins account for 50% of the cell wall.
a) True
b) False
View Answer
Explanation: Proteins account for 5 – 10 % of the cell wall. The cell wall proteins are represented by structural proteins, enzymes, and surface receptor proteins. Structural proteins involve mannoproteins. Enzymes are also divided into two groups. Lectin-like proteins represent the surface receptor proteins.
14. Mannoproteins implicated the cell wall porosity.
a) True
b) False
View Answer
Explanation: Mannoproteins also implicate the cell wall porosity. The mannoproteins in the cell wall obstruct or block the diffusion through ionic interactions and the web of mannan side chains.
Sanfoundry Global Education & Learning Series – Fermentation Technology.
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