This set of Environmental Biotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Microbes in Bioleaching Process”.
1. Microbially catalyzed redox reaction leads to metal ________
a) Mobilization
b) Immobilization
c) Reduction
d) Oxidation
View Answer
Explanation: Microbially catalyzed redox reaction leads to metal mobilization that is known as bioleaching. The metal oxidizing bacteria takes in electrons from the metals and leaves behind oxidized metal that causes metal mobilization.
2. Which of the following is the most common bacteria used for bioleaching?
a) Spirillum
b) Coccus
c) Bacillus
d) Streptococcus
View Answer
Explanation: Bacillus is the commonly used bacteria is bioleaching. This is most commonly used bioleaching as it is one of the most widely available bacteria and most effective for metal solubilization.
3. Which one of the following is not included in the mechanism of bioleaching?
a) Acidolysis
b) Complexolysis
c) Redoxolysis
d) Hydrolysis
View Answer
Explanation: The mechanisms of bioleaching includes acidolysis, complexolysis and redoxolysis. Acidolysis is the formation of organic and inorganic acids while hydrolysis is the formation of water. In bioleaching the mechanism is mostly involved with the formation of organic and inorganic acid instead of formation of water. Hence, hydrolysis is not included as one the major mechanism.
4. What kind of bacteria benefits the most from direct leaching?
a) Autotrophs
b) Heterotrophs
c) Chemotrophs
d) Chemolithotrophs
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Explanation: Autotrophs benefits the most from direct leaching. Direct leaching conserve energy duringoxidation of solids hence, they are beneficial for autotrophs.
5. Which genera helps in bioaccumulation?
a) Bacillus
b) Aspergillus
c) Agaricus
d) Mycenae
View Answer
Explanation: Bioaccumulation is a process of fungal bioleaching in which the mycelium of the fungi accumulates the heavy ions. Bacillus is a genus of bacteria and not fungi and among the other three options the genera of Aspergillus have high ability to accumulate heavy metal from the external environment.
6. What kind of pH is most suitable for bioleaching in majority of the metals?
a) At very low pH
b) At very high pH
c) At low pH
d) At high pH
View Answer
Explanation: High pH, be it high or very high is not suitable for bioleaching. Now coming to very low pH, it will destruct the metal rather than just leaching. Hence, low pH is the most favorable condition for bioleaching is at low pH as it enhances metal solubility.
7. Microbes that exhibit a low tolerance or have become adapted to low concentrations of soluble heavy metals in the leach suspension should be selected for bioleaching.
a) True
b) False
View Answer
Explanation: Microbes that exhibit a high tolerance or have become adapted to high concentrations of soluble heavy metals in the leach suspension should be selected for bioleaching. This is because microbes of different genus or different strains of same species show different sensitivities to different heavy metals.
8. Which among the following is the most suitable particle size of solid waste?
a) Order of few tens of millimeter
b) Order of few tens of centimeter
c) Order of few tens of micrometer
d) Order of few tens of decimeter
View Answer
Explanation: Decrease in particle increases the surface area that increases the contact area between the leaching agents and solid particle. Consequently, small solid particles increase the rate of leaching and its yield. Therefore, various experiments prove that highest solubilization rates have been found to occur in particles of sizes of the order of few tens of microns (Rossi, 1990).
9. Which of the following microbial leaching techniques depend on the working volume of less than ten cubic meter (<10m3)?
a) Laboratory Scale
b) Pilot-Plant Scale
c) Industrial Scale
d) Commercial Scale
View Answer
Explanation: Microbial leaching techniques are divided into three main groups depending on their working volume- Laboratory Scale, Pilot-Plant Scale & Industrial Scale. Pilot plant scale is concerned with <103 while laboratory scale is concerned with upto 10dm3 and industrial scale with >10m³. Commercial Scale is not a part of the three techniques.
10. FCC stands for _________
a) Fluid Cracking Catalyst
b) Fluid Catalytic Cracking
c) Fluid Chemical Cracking
d) Fluid Chemical Catalyst
View Answer
Explanation: The full form of FCC is Fluid Catalytic Cracking. It is very important conversion process that is used in petrol refinery. This is used in the conversion of LPG to Diesel.
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