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What is the purpose of using selective conditions in enrichment liquid culture?
What is the purpose of using selective conditions in enrichment liquid culture?
In a batch enrichment technique, the selective force may change over time, affecting the growth of undesired bacteria.
In a batch enrichment technique, the selective force may change over time, affecting the growth of undesired bacteria.
True
What technique is used to maintain cell populations in the exponential phase for extended periods?
What technique is used to maintain cell populations in the exponential phase for extended periods?
Chemostat
The _____ enrichment technique allows fresh medium to be added continuously to the culture broth.
The _____ enrichment technique allows fresh medium to be added continuously to the culture broth.
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What is a significant problem with the batch enrichment technique?
What is a significant problem with the batch enrichment technique?
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Match the enrichment methods with their descriptions:
Match the enrichment methods with their descriptions:
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The maximum specific growth rate (µmax) is always indicative of the most useful microorganism.
The maximum specific growth rate (µmax) is always indicative of the most useful microorganism.
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What step can be repeated several times to isolate the dominant organism in a batch enrichment technique?
What step can be repeated several times to isolate the dominant organism in a batch enrichment technique?
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What is one of the primary objectives of isolating industrially important microorganisms?
What is one of the primary objectives of isolating industrially important microorganisms?
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Researchers exclusively isolate microorganisms from commercial culture collections.
Researchers exclusively isolate microorganisms from commercial culture collections.
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What does the dilution rate (D) represent in a continuous enrichment technique?
What does the dilution rate (D) represent in a continuous enrichment technique?
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In a chemostat system at steady state, the rate of formation of new biomass is greater than the loss of cells.
In a chemostat system at steady state, the rate of formation of new biomass is greater than the loss of cells.
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What are two criteria used for selecting microorganisms?
What are two criteria used for selecting microorganisms?
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What is the primary purpose of preserving industrially important microorganisms?
What is the primary purpose of preserving industrially important microorganisms?
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Microorganisms isolated from extreme environments, such as hot springs or deep-sea vents, may produce new ________.
Microorganisms isolated from extreme environments, such as hot springs or deep-sea vents, may produce new ________.
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Continuous enrichment technique is used to isolate microorganisms by maintaining a _____ concentration.
Continuous enrichment technique is used to isolate microorganisms by maintaining a _____ concentration.
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Match the following culture collections with their focus:
Match the following culture collections with their focus:
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Which of the following is NOT a criterion for selecting microorganisms?
Which of the following is NOT a criterion for selecting microorganisms?
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Match the following preservation methods with their descriptions:
Match the following preservation methods with their descriptions:
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Enrichment liquid culture is a method used for microbial isolation.
Enrichment liquid culture is a method used for microbial isolation.
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Which of the following factors influences the growth rate of microbes in continuous culture?
Which of the following factors influences the growth rate of microbes in continuous culture?
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Only microorganisms that produce enzymes can grow on selective media.
Only microorganisms that produce enzymes can grow on selective media.
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Name one characteristic that makes a microorganism more amenable to genetic manipulation.
Name one characteristic that makes a microorganism more amenable to genetic manipulation.
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What occurs when dX equals zero in a continuous enrichment culture?
What occurs when dX equals zero in a continuous enrichment culture?
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What is the main purpose of secondary drying in the lyophilization process?
What is the main purpose of secondary drying in the lyophilization process?
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What is the preferred storage temperature for bacteria and yeast culture in glycerol?
What is the preferred storage temperature for bacteria and yeast culture in glycerol?
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The potential productivity of a microbial strain is only influenced by external factors like temperature and pressure.
The potential productivity of a microbial strain is only influenced by external factors like temperature and pressure.
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Cells stored in liquid nitrogen can last indefinitely without any cryoprotective agents.
Cells stored in liquid nitrogen can last indefinitely without any cryoprotective agents.
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What is lyophilization commonly used for in microbiology?
What is lyophilization commonly used for in microbiology?
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What is the process called that removes water from microorganisms during preservation?
What is the process called that removes water from microorganisms during preservation?
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The process of inoculating a culture onto a suitable medium is called __________.
The process of inoculating a culture onto a suitable medium is called __________.
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Which of the following methods is NOT a way to achieve genetic modification in microorganisms?
Which of the following methods is NOT a way to achieve genetic modification in microorganisms?
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During the lyophilization process, the first step is known as _____ .
During the lyophilization process, the first step is known as _____ .
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Match the preservation method with its characteristic technique:
Match the preservation method with its characteristic technique:
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Match the following terms with their correct definitions:
Match the following terms with their correct definitions:
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Natural variants produced during cell division are usually superior producers compared to the original culture.
Natural variants produced during cell division are usually superior producers compared to the original culture.
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What is the primary advantage of slowly freezing cells before storage?
What is the primary advantage of slowly freezing cells before storage?
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The lyophilization process passes water through the liquid state before removal.
The lyophilization process passes water through the liquid state before removal.
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What is one limitation of optimizing culture medium to increase yield?
What is one limitation of optimizing culture medium to increase yield?
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Name one protective medium used during the resuspension of cells for lyophilization.
Name one protective medium used during the resuspension of cells for lyophilization.
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What is one characteristic of microbes that makes them suitable for industrial applications?
What is one characteristic of microbes that makes them suitable for industrial applications?
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Induced mutants can be selected by exposing cells to mutagenic agents.
Induced mutants can be selected by exposing cells to mutagenic agents.
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What process allows for the generation of new gene combinations from different individuals?
What process allows for the generation of new gene combinations from different individuals?
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Microbes can be selected for their ability to produce enzymes without the addition of __________.
Microbes can be selected for their ability to produce enzymes without the addition of __________.
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Match the following selection criteria with their descriptions:
Match the following selection criteria with their descriptions:
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Study Notes
Bioprocess Technology - Topic 4: Isolation, Preservation and Strain Improvement
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Lecture Outline:
- Techniques for isolating industrially important microorganisms
- Criteria for selecting microorganisms
- Preservation methods for industrially important microorganisms
- Genetic modification of bacterial strains
Isolation of Industrially Important Microorganisms
- First Stage in Fermentation: Screening microbes with potential industrial applications to obtain pure or mixed cultures. The objective is to carry out desired reactions or product creation.
- Microbe Selection: A balance between microbe productivity and economic process constraints.
- Sources of Desired Microbes: Natural resources and culture collections. The question is, is it cheaper to buy microorganisms or to isolate them and which is more desirable?
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Major Culture Collections:
- National Collection of Type Cultures (NCTC)
- National Collection of Yeast Cultures (NCYC)
- American Type Culture Collection (ATCC)
Criteria in Selection of Microorganisms
- Nutritional Characteristics: Ideal nutritional requirements.
- Optimum Growth Temperature: Optimal temperature for growth.
- Compatibility with Equipment: How the microorganism interacts with available equipment and suitability for the intended process.
- Genetic Manipulation: Stability of an organism and ease of genetic manipulation.
- Productivity: Efficiency of microorganism production.
- Ease of Product Recovery: How easily the desired product can be retrieved.
- Product Quality: Quality specifications of produced goods.
Isolation of Microorganisms
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Researchers' Goal: Isolating strains from extreme or unusual environments in hopes of finding strains producing new metabolites.
- Examples from extreme conditions: High altitudes, cold habitats, sea water, hot springs, deserts, petroleum fields, etc.
- Types of microbes from extreme conditions: Acidophiles, psychrophiles, thermophiles, anaerobes, halophiles.
- Examples from extreme conditions: High altitudes, cold habitats, sea water, hot springs, deserts, petroleum fields, etc.
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Isolation Methods:
- Selective pressure/force – select desired characteristics
- Isolation of organisms that will grow on a particular substrate or in the presence of certain compounds
- Two different methods: Enrichment liquid culture and using solidified media.
Enrichment Liquid Culture
- Batch Enrichment: Providing specific conditions (supply of substrate or inhibitors) to a mixed population to encourage the growth of desired microbes.
- Enrichment Problems: Changes in selective force may lead to undesired bacteria growing. Ex: the excretory product of microbe A might cause the growth of microbe B.
- Repeated Sub-culturing: Re-establishing selective force by inoculating the enriched culture into a fresh medium several times before isolating the dominant organism by spreading a small inoculum on solid medium.
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Continuous Enrichment:
- Chemostat Culture: Constant volume system for continuous addition of fresh medium and removal of culture medium and cells at a constant rate. A device to keep cell populations in exponential phase for a long period.
- Dilution Rate (D): Flow rate of medium into the vessel divided by the volume of the culture medium.
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Steady State Conditions: The system has reached equilibrium, new biomass formed balances loss of cells from the vessel, and the net change of cell concentration remains constant over time.
- D = Change in cell concentration over change in time
- μX - DX = 0
- μ = specific growth rate; X = cell concentration; D = dilution rate
- D = Change in cell concentration over change in time
The Use of Solidified Media
- Direct Testing: Testing biological activity directly on a plate.
- Colony Isolation: Isolating only colonies that show activity.
- Selective Media: Usually using selective media (substrate for the enzyme), which encourages the growth of the producing enzyme.
Preservation of Industrially Important Microorganisms
- Purpose: Maintaining viability, avoiding contamination, and maintaining microbial behavior/properties.
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Three Methods:
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Storage at Reduced Temperature:
- Agar slopes
- Spore suspensions
- Cell suspensions
- Liquid Nitrogen
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Storage in a Dehydrated Form (Lyophilized):
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Freeze-drying process which removes water as vapor, without passing through liquid state.
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Steps for lyophilization: Grow culture to maximum stationary phase → Resuspend cells in a protective medium (e.g., skimmed milk, sucrose, serum) → Freeze dry to complete sublimation → Seal ampoule in situ → Store in an appropriate refrigerator (e.g., at -20, -70 or -80°C).
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- Subculture: Inoculation of a culture onto a suitable medium contained in a tube or bottle. The process can be repeatedly performed at intervals to produce a fresh culture before the old one dies.
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Storage at Reduced Temperature:
Improvement of Industrial Microbes
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Increasing Yield and Productivity:
- Optimizing culture medium and growth conditions.
- Genetic Modification: Modifying the genome to increase the potential yield.
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Methods for Genetic Modification:
- Selection of natural variants
- Monospore isolation (using solidified media, each colony is tested for product production and potential production capabilities)
- Selecting induced mutants
- Treatment with mutagenic agents (e.g., UV radiation) to a high mortality rate, then survivors are cultured for superior characteristics.
- Selecting recombinants
- Combining new genes from different individuals.
- Selection of natural variants
- Additional Improvement: Selection of stable strains, resistance to infection, non-foaming strains, tolerant to low oxygen tension, elimination of undesirable products.
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Description
Test your knowledge on microbial enrichment techniques, including batch and continuous methods. This quiz covers the purposes, challenges, and specific growth rates associated with different enrichment strategies. Perfect for students studying microbiology.
