This set of Advanced Enzyme Technology Questions and Answers focuses on “Recent Advances – Enzyme Kinetics in Biphasic Aqueous-Organic Systems”.
1. In a biphasic system, the thickness of the aqueous layer (δ) around an immobilised enzyme lowers the rate of reaction.
a) True
b) False
View Answer
Explanation: In biphasic systems, reactants may have fairly low aqueous solubilities under normal conditions. The aqueous phase remains effectively unstirred, while the organic phase is well-stirred so that the thickness of the ‘unstirred layer’ (δ) is equal to the thickness of the aqueous layer surrounding the enzyme.
• When δ is large, it leads to the passage of reactants through aqueous layer due to formation concentration gradient which will be very shallow. This the result of the reactants being less soluble in water.
• If δ is small, the enzyme is freely soluble, causing the reactants from the more concentrated organic phase through the interphase boundary to very low concentrations within the microenvironment of the enzyme.
This shows that the thickness of the aqueous layer around an immobilized enzyme is important and determines the degree of diffusional resistance involved. Thus, lowering the reaction rate. Hence the above statement is true.
2. For immobilized enzymes, the volumetric surface area (A/V) is an important parameter which does not govern which of the following?
a) The overall flux of the substrate to the biocatalytic surface
b) Effectiveness of the enzyme
c) Recovery of the biocatalyst
d) Productivity
View Answer
Explanation: For immobilized enzymes, the following things are governed by the volumetric surface area (A/V) is an important parameter:
• The overall flux of the substrate to the biocatalytic surface,
• The effectiveness of the enzyme and
• productivity.
Recovery of the biocatalyst is an advantage of impregnated wet beads along with some others which are as follows:
• Protection of the contained enzyme at higher rates of stirring.
• Allows to be used with low molecular weight hydrophilic coenzymes with the assistance of a coenzyme regenerating process.
• Allowing efficient and continuous use of biphasic PBRs as long as the moving organic phase is saturated with water.
3. Which of this is true for optimizing a two-phase system for enzyme-catalyzed reactions?
a) Protection of the contained enzyme
b) More facile recovery of the biocatalyst
c) The difference between the Log P values of the substrates and the interphase should be as small as possible
d) Allowing efficient and continuous use of biphasic PBRs
View Answer
Explanation: The optimization of the two-phase system for enzyme-catalyzed reactions depends upon the concept of Log P being extended to cover the substrates, products and the interphase. The difference between the Log P values of the substrates and the interphase should be as small as possible, whereas the Log P values is much lower between substrates and organic phase. This leads to high concentrations of substrates within the interphase, and in turn transferring of a substrate from the organic phase into the aqueous phase.
4. Which of the following rule belongs to optimization of the two-phase system for enzyme-catalyzed reactions?
a) The difference between the Log P values of the products and the organic phase should be as small as possible
b) Allows to be used with low molecular weight hydrophilic coenzymes with the assistance of a coenzyme regenerating process
c) Allowing efficient and continuous use of biphasic PBRs as long as the moving organic phase is saturated with water
d) Allowing efficient and continuous use of biphasic PBRs
View Answer
Explanation: The concept of Log P being extended to cover the substrates, products and the interphase is used for optimization of the two-phase system for enzyme-catalyzed reactions. The difference between the Log P values of the products and the organic phase should be as small as possible, whereas the Log P values are much greater than that of products and interphase which helps in encouraging the transfer of the product from the aqueous phase through the interphase into the organic phase, after the reaction.
5. In the biphasic system, which of the following methodology is not used to remove the excess water present?
a) Use of hydrolases
b) Chromatography
c) Use of molecular sieves
d) Vacuum distillation
View Answer
Explanation: The methodologies used to remove the excess water present are as follows:
• Use of hydrolases.
• Use of molecular sieves which absorbs water.
• Vacuum distillation, if the organic phase has a high boiling point.
Chromatography is used for separation of a mixture which is dissolved in a fluid called the mobile phase and carrying it through a structure holding another material called the stationary phase. The separation is based on differential partitioning between the mobile and stationary phases.
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