This set of Enzyme Technology Multiple Choice Questions & Answers (MCQs) focuses on “High Fructose Corn Syrups and use of Immobilized Raffinase, Invertase and Lactase”.
1. Production of DE glucose syrup using glucoamylase has shortcomings as an object of commerce.
a) True
b) False
View Answer
Explanation: D-glucose has 70% sweetness of sucrose and is comparatively insoluble. 97 DE glucose must be either kept warm to prevent crystallization or dilute the concentration to avoid microbial interactions. On the contrary, Fructose is 30% sweeter than fructose and twice as soluble as glucose at low temperatures so a 50% conversion of glucose to fructose overcomes both problems giving a stable syrup that is as sweet as a sucrose solution of the same concentration. Hence the above statement is true.
2. Glucose is converted to fructose by _________ enzyme.
a) lactase
b) phosphorylase
c) glucose isomerase
d) raffinase
View Answer
Explanation: Glucose is converted to fructose in an isomerization reaction catalyzed by glucose isomerase. Lactase is used to catalyze the hydrolysis of lactose to glucose and galactose. Raffinase catalyzes the hydrolysis of raffinose. Phosphorylase is an enzyme that introduces a phosphate group into an organic molecule, notably glucose.
3. What does ‘X’ represent in the following reaction?
Starch (Gn) + orthophosphate \( \underset{x}{\rightleftharpoons}\) Starch (Gn-1) + α – glucose – 1- phosphate
a) Lactase
b) Invertase
c) Phosphorylase
d) Raffinase
View Answer
Explanation: In the above reaction, ‘X’ represents phosphorylase which introduces a phosphate group into an organic molecule. Lactase converts lactose to glucose and galactose. Invertase is an enzyme produced by yeast which catalyzes the hydrolysis of sucrose, forming invert sugar. The enzyme which catalyzes hydrolysis of raffinose is called raffinase.
4. _____________ isomerizes α-D-glucopyranose to α-D –fructofuranose.
a) Xylose isomerase
b) Glucose isomerase
c) Sucrose phosphorylase
d) Invertase
View Answer
Explanation: The enzyme which isomerizes α-D-glucopyranose to α-D –fructofuranose is xylose isomerase. Whereas glucose isomerase isomerizes glucose to fructose. Sucrose phosphorylase converts fructose to sucrose releasing orthophosphate. Invertase catalyzes the hydrolysis of sucrose.
5. Which of the following organism is capable of producing raffinase, but not invertase.
a) Yeast
b) Mortierella vinacea
c) Bacillus acidopullulyticus
d) Kluyveromyces lactis
View Answer
Explanation: Mortierella vinacea is capable of producing raffinase, but not invertase. Raffinase catalyzes the hydrolysis of raffinose. Yeast is used to produce invertase. Pullulanase is produced by Bacillus acidopullulyticus. Kluyveromyces lactis produces lactase.
6. ____________ is stirred with sugar beet juice in batch stirred tank reactors to remove raffinose.
a) Kluyveromyces lactis
b) Bacillus Licheniformis
c) Mortierella vinacea
d) Bacillus acidopullulyticus
View Answer
Explanation: Mortierella vinacea is stirred with sugar beet juice in batch stirred tank reactors to remove raffinose. The galactose released is destroyed in the alkaline conditions of the first stages of juice purification and does not cause any further problems while the sucrose is recovered. Kluyveromyces lactis produces lactase. Bacillus Licheniformis produces amylases. Pullulanase is produced by Bacillus acidopullulyticus.
7. Immobilized __________ is used to remove the raffinose and stachyose from soybean milk.
a) raffinase
b) xylose isomerase
c) invertase
d) papain
View Answer
Explanation: Immobilized raffinase is used to remove the raffinose and stachyose from soybean milk. Raffinose and stachyose are responsible for the flatulence that may be caused when soybean milk is used as a milk substitute in special diets. Hence their removal becomes necessary. Xylose isomerase isomerizes α-D-glucopyranose to α-D –fructofuranose. Invertase catalyzes the hydrolysis of sucrose. Papain is used in meat tenderization and is a proteolytic enzyme.
8. Which one of the following is not a step in production of glucose syrups using invertase?
a) Yeast cells were autolyzed
b) Filtration through a bed of calcium sulphate
c) Adsorption into bone char
d) Galactose released is destroyed by alkaline conditions
View Answer
Explanation: The steps involved in production of glucose syrup using invertase are as follows:
• Yeast cells were autolyzed.
• Autolyzate clarified by adjustment to pH 4.7.
• Filtration through a bed of calcium sulphate.
• Adsorption into bone char which helps in decolorizing the syrups.
Galactose released is destroyed by alkaline conditions of the first stages of juice purification and does not cause any further problems while the sucrose is recovered. This is stage in removal of raffinose and not production of glucose syrups.
9. A productivity of 16 tons of inverted syrup may be achieved using one liter of the granular enzyme.
a) True
b) False
View Answer
Explanation: The above statement is true. As it is difficult to produce syrups of equivalent quality by acid hydrolysis. Also, enzymic inversion avoids the problems of acid hydrolysis such as high-color, high salt-ash, relatively low conversion, batch variability, etc. Free invertase with residence times of about a day may be used. But the use of immobilised enzymes with a residence time of about 15 min in a PBR helps make the process competitive and the cost of 95% inversion being not more than the final evaporation costs.
10. Immobilized ______________ is used in the treatment of whey.
a) raffinase
b) lactase
c) invertase
d) rennet
View Answer
Explanation: Immobilized lactase is used in the treatment of whey as the fats and proteins in the milk emulsion tend to coat the biocatalyst which reduces their apparent activity and increases the chances microbial colonization. Immobilized raffinase is used to remove raffinose. Whereas immobilized invertase helps in production of glucose syrups. Rennet is used in cheese making industry.
11. Which of the following immobilized organism is not used to produce lactases?
a) Kluyveromyces lactis
b) Mortierella vinacea
c) Aspergillus Niger
d) Aspergillus Oryzae
View Answer
Explanation: Immobilized Mortierella vinacea produces raffinase which helps in the removal of raffinose. Kluyveromyces lactis is immobilized on cellulose triacetate fibers in batch wise stir tanked reactor to produce lactase. Aspergillus Niger, Aspergillus Oryzae are immobilized porous silica using glutaraldehyde and γ-aminopropyltriethoxysilane in a packed bed reactor to produce lactases.
12. Which of the following is not true for immobilized lactases?
a) Product inhibition by galactose
b) Unwanted oligosaccharide formation
c) Microbial contamination
d) Batch variability problems of acid hydrolysis
View Answer
Explanation: Batch variability problems of acid hydrolysis comes into picture when syrups are being produced by using acid hydrolysis process rather than the use of immobilized enzymes. The following is true for immobilized lactases:
• Product inhibition by galactose and unwanted oligosaccharide
This may be reduced by increasing the effectiveness factor and a reduction in the degree of hydrolysis or initial lactose concentration which may also lead to a reduction in the economic return.
• Microbial contamination
This can be controlled by the use of regular sanitation with basic detergent and a dilute protease solution.
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