biology : class12 Hydrocarbon-Utilizing Microbes : Definition, Sources, Nutritional Importance : Single Cell Protein MCQ Questions and Answers
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Hydrocarbon-Utilizing Microbes
MCQ questions and answers.
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MCQ Questions
1. In the production of single-cell protein from petroleum hydrocarbons, which substrate is generally most suitable for rapid microbial growth because it is readily oxidized by many hydrocarbon-utilizing microbes?
A.
Long-chain n-alkanes
B.
Highly condensed polycyclic aromatic hydrocarbons
C.
Inorganic nitrate crystals
D.
Cellulose fibres without prior hydrolysis
Correct Answer:
Long-chain n-alkanes
Explanation:
Many hydrocarbon-utilizing bacteria and yeasts can oxidize n-alkanes efficiently, making them useful carbon and energy sources for producing microbial biomass and single-cell protein. Condensed aromatic hydrocarbons are generally more resistant to microbial degradation.
2. Which initial biochemical event is most directly required when a microorganism begins utilizing an n-alkane as its carbon source?
A.
Hydroxylation of the alkane to form an alcohol
B.
Conversion of the alkane directly into amino acids without oxidation
C.
Reduction of the alkane into methane
D.
Polymerization of the alkane into cellulose
Correct Answer:
Hydroxylation of the alkane to form an alcohol
Explanation:
Hydrocarbon-utilizing microbes commonly initiate n-alkane degradation by introducing oxygen into the hydrocarbon through hydroxylation, producing an alcohol that can subsequently be oxidized and assimilated.
3. Why must oxygen transfer be carefully controlled in an aerobic culture producing single-cell protein from hydrocarbons?
A.
Oxygen is required for enzymatic oxidation of the hydrocarbon substrate
B.
Oxygen prevents the microorganism from synthesizing cellular protein
C.
Oxygen converts all hydrocarbons into inorganic nitrogen
D.
Oxygen is needed only to sterilize the final biomass
Correct Answer:
Oxygen is required for enzymatic oxidation of the hydrocarbon substrate
Explanation:
The initial activation and subsequent oxidation of hydrocarbons generally require molecular oxygen. Therefore, adequate oxygen transfer is essential for both substrate utilization and efficient biomass formation.
4. Which microbial characteristic is most desirable when selecting an organism for single-cell protein production using petroleum-derived hydrocarbons?
A.
High biomass yield with low accumulation of toxic hydrocarbon intermediates
B.
Inability to grow in the presence of hydrocarbons
C.
Exclusive production of extracellular oil instead of biomass
D.
Dependence on complex animal tissues as the carbon source
Correct Answer:
High biomass yield with low accumulation of toxic hydrocarbon intermediates
Explanation:
A suitable hydrocarbon-utilizing microbe should convert the substrate efficiently into safe, protein-rich biomass while minimizing the accumulation of toxic intermediates that could compromise the usability of the single-cell protein.
5. A yeast strain grows rapidly when supplied with n-alkanes but fails to grow when supplied with benzene as the sole carbon source. What does this result most directly indicate?
A.
The strain has substrate specificity for certain hydrocarbons
B.
The strain cannot perform any oxidative metabolism
C.
Benzene is always a superior substrate for microbial protein production
D.
n-Alkanes cannot provide carbon for microbial growth
Correct Answer:
The strain has substrate specificity for certain hydrocarbons
Explanation:
Different hydrocarbons require different enzymes and metabolic pathways. Growth on n-alkanes but not benzene indicates that the organism can utilize the former but lacks the necessary capacity to degrade or assimilate the latter.
6. Which combination best explains the nutritional importance of biomass produced by hydrocarbon-utilizing microbes?
A.
Rapidly formed microbial biomass can contain substantial cellular protein and essential nutrients
B.
The biomass consists almost entirely of unchanged petroleum hydrocarbons
C.
The biomass is nutritionally useful only because it contains no nucleic acids
D.
The biomass has value only as an inorganic fertilizer and not as a protein source
Correct Answer:
Rapidly formed microbial biomass can contain substantial cellular protein and essential nutrients
Explanation:
When hydrocarbons are converted into microbial cells, the resulting biomass may be rich in protein and can contain vitamins and other nutrients. Its nutritional value depends on safe processing and suitable composition.
7. Which process-control problem is especially important when hydrocarbons are used as substrates for single-cell protein production?
A.
Maintaining adequate dispersion of the poorly water-soluble hydrocarbon
B.
Preventing all contact between the microbe and its carbon source
C.
Removing atmospheric nitrogen before inoculation
D.
Ensuring that the culture contains no oxygen at any stage
Correct Answer:
Maintaining adequate dispersion of the poorly water-soluble hydrocarbon
Explanation:
Many hydrocarbons have low water solubility, which limits contact between the substrate and microbial cells. Proper dispersion and mass transfer improve substrate availability and support efficient microbial growth.
8. A hydrocarbon-utilizing microorganism converts a petroleum fraction into biomass but leaves a large amount of toxic aromatic residue. Which conclusion is most appropriate for its use as a single-cell protein producer?
A.
The biomass requires safety evaluation and possible downstream treatment before use
B.
The residue proves that the biomass is automatically suitable for human consumption
C.
The organism has converted the residue into harmless protein by definition
D.
The presence of residue means that hydrocarbon utilization did not occur
Correct Answer:
The biomass requires safety evaluation and possible downstream treatment before use
Explanation:
Incomplete degradation can leave toxic hydrocarbons or intermediates associated with the biomass or culture medium. Therefore, nutritional safety and removal of residual contaminants must be assessed before the product is used as single-cell protein.
9. Why can hydrocarbon-utilizing bacteria and yeasts produce single-cell protein at a comparatively high rate under suitable conditions?
A.
They combine rapid microbial multiplication with direct conversion of reduced hydrocarbon carbon into cellular material
B.
They obtain all cellular nitrogen by chemically converting hydrocarbons into nitrate
C.
They do not require minerals or nitrogen for protein synthesis
D.
They reproduce only after petroleum has been completely converted into glucose
Correct Answer:
They combine rapid microbial multiplication with direct conversion of reduced hydrocarbon carbon into cellular material
Explanation:
These microorganisms can grow rapidly and use hydrocarbons as carbon and energy sources. With an adequate supply of nitrogen and minerals, a significant fraction of the substrate carbon can be incorporated into microbial biomass, including protein.
10. Which statement best distinguishes the role of a hydrocarbon-utilizing microbe from the role of the hydrocarbon substrate in single-cell protein production?
A.
The microbe supplies the protein-rich biomass, whereas the hydrocarbon primarily supplies carbon and energy
B.
The hydrocarbon supplies preformed microbial enzymes, whereas the microbe supplies only water
C.
The microbe is converted into petroleum, whereas the hydrocarbon supplies amino acids directly
D.
Both the microbe and the hydrocarbon are merely sterilizing agents in the culture
Correct Answer:
The microbe supplies the protein-rich biomass, whereas the hydrocarbon primarily supplies carbon and energy
Explanation:
Hydrocarbons serve mainly as carbon and energy sources. The microorganism metabolizes them and synthesizes its own cellular constituents, producing the protein-rich microbial biomass known as single-cell protein.
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