Microbial Technology Processes
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Questions and Answers

What is the main limitation of a bioprocess where no additional nutrients are added?

  • Limited biomass and product yields (correct)
  • The risk of contamination
  • Complex nutrient management
  • High operational costs

    • In batch processes, the medium and biomass are harvested simultaneously at the end of the bioprocess run.

    False (B)

    What is a characteristic of a fed-batch process?

  • Substrates are added continuously.
  • All nutrients are provided at once.
  • Feeding can extend culture duration. (correct)
  • Extra feeding is not used.

    • What is the purpose of increasing the stirring speed during a bioprocess?

    <p>To improve the availability of dissolved oxygen.</p> Signup and view all the answers

    In a continuous culture, the feed rate of a substrate must always be constant.

    <p>False (B)</p> Signup and view all the answers

    In batch processes, the presence of high concentrations of substrate or product can lead to __________, reducing yield.

    <p>metabolic feedback</p> Signup and view all the answers

    Match the following parameters with their roles in improving dissolved oxygen concentration:

    <p>Stirring Speed = Increases oxygen transfer rate Gas Flow = Enhances gas-liquid interface Oxygen Proportion = Increases the amount of oxygen available Pressure = Helps dissolve more gases in liquid</p> Signup and view all the answers

    What type of culture provides all nutrients at the beginning without further additions?

    <p>Batch process</p> Signup and view all the answers

    In a _____ culture, the incoming feed rate matches the rate of removal of harvest.

    <p>continuous</p> Signup and view all the answers

    Which of the following is a disadvantage of batch processes?

    <p>Increased risk of product inhibition (A)</p> Signup and view all the answers

    Match the following processes with their characteristics:

    <p>Batch = No extra feeding after initial nutrient supply Fed-batch = Feeding extends culture duration for higher densities Continuous = Feed rate adjusts based on cell density Repeated Fed-batch = Harvesting with cells remaining for next batch</p> Signup and view all the answers

    The bioprocess lasts as long as the microorganisms are in the exponential growth phase.

    <p>False (B)</p> Signup and view all the answers

    Which of the following accurately describes a chemostat?

    <p>Cell density is determined by the feed rate. (B)</p> Signup and view all the answers

    What do sophisticated management processes, known as cascades, aim to do in bioprocessing?

    <p>Adjust concentration of dissolved oxygen.</p> Signup and view all the answers

    What is the primary goal of utilizing different bioprocess methods?

    <p>To optimize the growth conditions and maximize product yield.</p> Signup and view all the answers

    What is a significant disadvantage of the fed-batch process?

    <p>It allows the accumulation of toxic by-products. (D)</p> Signup and view all the answers

    In a repeated fed-batch process, all cells are removed after harvesting.

    <p>False (B)</p> Signup and view all the answers

    The fed-batch process is considered a discontinuous process.

    <p>False (B)</p> Signup and view all the answers

    What effect can high glucose concentrations have on baker's yeast during the batch process?

    <p>Inhibition of growth due to the formation of ethanol.</p> Signup and view all the answers

    A fed-batch process can be used to switch genes on or off by changing the __________.

    <p>substrate</p> Signup and view all the answers

    Match the advantages and disadvantages of fed-batch processes:

    <p>Extends a culture’s productive duration = Allows build up of inhibitory agents and toxins Can be used to switch genes on or off = Provides another point of ingress for contamination Can be manipulated for maximum productivity = May create bottlenecks in downstream processing</p> Signup and view all the answers

    Which of the following applications commonly uses fed-batch processes?

    <p>Production of recombinant proteins (A)</p> Signup and view all the answers

    The Crabtree effect occurs at low glucose concentrations.

    <p>False (B)</p> Signup and view all the answers

    What is a potential problem with high cell density numbers produced in fed-batch processes?

    <p>They can create bottlenecks in downstream processing.</p> Signup and view all the answers

    What is the main advantage of a fed-batch process?

    <p>It prevents the carbon source from being exhausted. (A)</p> Signup and view all the answers

    In continuous culture, the inflow and outflow rates must be greater than the doubling time of the microorganisms.

    <p>False (B)</p> Signup and view all the answers

    What does the term 'steady state' refer to in the context of continuous culture?

    <p>An equilibrium established between inflow and outflow rates.</p> Signup and view all the answers

    In a perfusion process, cells can be retained using a __________.

    <p>spin filter</p> Signup and view all the answers

    Match the following bioprocesses with their definitions:

    <p>Fed-batch = Adding feed after the exponential phase Continuous culture = Steady state with balanced inflow and outflow Perfusion = Retention of cells using external filters Chemostat = Continuous medium replacement at equal rates</p> Signup and view all the answers

    What occurs when an excess of nutrients is provided in a continuous culture?

    <p>Inhibition due to toxin buildup (C)</p> Signup and view all the answers

    Prolonged cultivation periods in continuous culture reduce the risk of contamination.

    <p>False (B)</p> Signup and view all the answers

    What is one disadvantage of the long cultivation period in a continuous culture?

    <p>Increased risk of contamination.</p> Signup and view all the answers

    What is the primary purpose of a repeated fed-batch culture?

    <p>To renew media and utilize carbon substrates (B)</p> Signup and view all the answers

    In a repeated fed-batch culture, a new cycle can begin when the existing carbon source is exhausted.

    <p>True (A)</p> Signup and view all the answers

    What percentage of the bioreactor volume is typically removed during a fed-batch cycle?

    <p>25 to 75 percent</p> Signup and view all the answers

    The remaining culture in the bioreactor acts as an ______ for the next batch.

    <p>inoculum</p> Signup and view all the answers

    What does the growth control in a fed-batch process mainly depend on?

    <p>Feed rate of the substrate (A)</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Repeated Fed-batch = Renewal of media after a batch Substrate accumulation = No active control on growth Inoculum = Existing culture used for the next batch Semi-continuous culture = Another term for repeated fed-batch</p> Signup and view all the answers

    All repeated processes in culture allow for active influence on growth.

    <p>False (B)</p> Signup and view all the answers

    What determines the number of cycles in a repeated fed-batch culture?

    <p>Required biomass</p> Signup and view all the answers

    What is a key advantage of repeated fed-batch culture compared to full continuous culture?

    <p>Less diluted culture effluent (A)</p> Signup and view all the answers

    Fed-batch culture is typically used for stable, long-duration studies.

    <p>False (B)</p> Signup and view all the answers

    What impact does the repeated fed-batch culture have on quality control?

    <p>Positive impact due to segregation of product into sub-batches.</p> Signup and view all the answers

    For fast, limited culture processes, use __________.

    <p>batch</p> Signup and view all the answers

    Which feeding strategy allows for precise control of nutrient addition in bioreactors?

    <p>Fed-batch (B)</p> Signup and view all the answers

    Match the culture types with their best application:

    <p>Batch = Fast, limited processes Fed-batch = High density, flexible productivity Continuous = Stable, long duration studies Repeated fed-batch = Quality control in sub-batches</p> Signup and view all the answers

    In repeated fed-batch cultures, the length is typically measured in weeks or months.

    <p>False (B)</p> Signup and view all the answers

    What must be controlled in continuous culture to maintain stability?

    <p>Feed rate of substrate</p> Signup and view all the answers

    Flashcards

    Batch Process

    A bioprocess where all nutrients are added at the start and no more are added later.

    Fed-batch Process

    A bioprocess where nutrients are added over time, to increase culture duration, cell density or produce different products.

    Continuous Culture

    A bioprocess where nutrients are constantly added and products constantly removed, maintaining steady state.

    Chemostat

    A type of continuous culture where the feed rate of a limiting nutrient keeps cell density constant.

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    Turbidostat

    A type of continuous culture where cell density determines the feed rate of a limiting nutrient.

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    Repeated Fed-batch

    A process where harvesting is done after a complete fed-batch, and the remaining cells are used to inoculate the next batch.

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    Substrate

    Nutrients required for microbial growth in a bioprocess.

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    Bioprocess

    A process that involves microorganisms to produce a product.

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    Batch Process Limitations

    Limited biomass and product yields because carbon source/oxygen often limits microbial growth to non-exponential phases..

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    Oxygen Transfer Enhancement

    Increasing stirring speed, gas flow, oxygen proportion in gas mixture, or pressure in bioreactor to enable more dissolved oxygen.

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    Bioreactor Control Cascades

    Sophisticated management and control of parameters to improve dissolved oxygen concentration.

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    Harvesting in Batch Processes

    Biomass or fermentation medium is harvested after batch process ends. Processing extracts desired products; process is interrupted by cleaning and sterilization.

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    Substrate/Product Inhibition

    High concentrations of substrate or product interfere with enzyme activity and can reduce product yield.

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    Closed Bioprocess System

    A system in a bioreactor where no further nutrients are added during the process; only control elements (gas, acids, bases) are used.

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    Strain Characterization

    Using batch processes to evaluate and assess specific types of microorganisms (strains) with respect to their growth and functional characteristics, like production of targeted products.

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    Substrate Inhibition

    A phenomenon where high substrate concentrations can hinder the growth of microorganisms or inhibit protein production by accumulation of toxic byproducts

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    Crabtree effect

    A phenomenon where microorganisms preferentially use glucose for fermentation over respiration when oxygen is sufficient.

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    Fed-batch advantages

    Prolonged culture life, substrate control for gene expression modification, and maximized productivity through different feeding strategies.

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    Fed-batch disadvantages

    Increased likelihood of inhibition or contamination due to increased production time and toxic buildup.

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    Biotechnological Production

    Using biological systems, especially microorganisms for the production of desired products like proteins or antibiotics

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    Recombinant proteins

    Proteins produced by genetically modified organisms, often for medicinal or industrial usage

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    Repeated Fed-batch Benefits

    Reduces toxin accumulation, maintains high yields, and allows for product quality control by separating batches.

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    Continuous Culture Applications

    Ideal for long-term, stable production of consistent products in controlled volumes.

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    Batch vs. Fed-batch vs. Continuous

    Batch: All nutrients added at start, Fed-batch: Nutrients added over time, Continuous: Constant nutrient input and product removal.

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    Choosing the Right Bioprocess

    The best choice depends on desired growth rate, product yield, and process stability.

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    Bioprocess Control

    Manipulating the feed composition and rates to optimize growth and product formation.

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    Importance of Feed Control

    Allows for precise control of various feeding strategies, maximizing yield and minimizing waste.

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    Semi-continuous Culture

    An alternative term for repeated fed-batch, highlighting the continuous nature of the process with regular partial harvest and replenishment.

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    Substrate Accumulation

    The goal of repeated Fed-batch processes where the primary focus is to accumulate a desired product or compound rather than maximizing cell growth.

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    Why Repeated Fed-batch?

    This method is preferred when maximizing product yield and controlling growth is not critical. It allows for extended production with accumulated products without needing a constant feed.

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    How does repeated Fed-batch compare to fed-batch?

    Unlike a fed-batch where the feed rate directly controls growth, repeated Fed-batch focuses on accumulating a product, with less active control over growth.

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    How many cycles in Repeated Fed-batch?

    The number of cycles is determined by the specific growth rate, substrate utilization profile, and the desired amount of biomass or product accumulation.

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    Harvesting in Repeated Fed-batch

    A portion of the culture is harvested after each complete fed-batch cycle, allowing for periodic product extraction.

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    Inoculum in Repeated Fed-batch

    The remaining culture after harvest serves as the starting point (inoculum) for the next cycle, effectively restarting the process.

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    Exponential feeding

    A feeding strategy in fed-batch processes where the nutrient addition rate increases exponentially, mirroring the growth rate of the cells, maximizing cell growth and production.

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    Perfusion

    A strategy in continuous culture where cells are retained within the bioreactor while fresh medium is continuously added and product is removed. This allows for high cell density and efficient production without cell loss.

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    Space-time yield

    An important metric in bioprocess engineering that measures the amount of product produced per unit volume of bioreactor per unit time. Higher space-time yield indicates more efficient use of resources.

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    Contamination risk

    The likelihood of unwanted microorganisms entering a bioprocess and potentially disrupting production. This risk increases in long-term cultivations like continuous processes.

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    Long-term changes

    In continuous cultures, microorganisms can adapt over time to their environment, potentially leading to changes in product quality, growth rate, or other characteristics.

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    Study Notes

    Microbial Technology: Batch, Continuous, and Fed-Batch Processes

    • A substrate is essential for all bioprocesses, even for algae needing mineral salts, light, and CO2. Typically, this is a sugar, added at the start or throughout the process. The best method depends on the organism, application, and desired outcome.

    Batch Processes

    • All nutrients are provided at the beginning of the process. No more are added.
    • The process continues until all the nutrients are used up.
    • This is suitable for quick experiments, like strain analysis and optimizing nutrient media.
    • Disadvantages include limited biomass and product yield because the limiting factor (carbon or oxygen transfer) isn’t met for long periods, so microorganisms aren't growing quickly enough.

    Batch Process Improvements

    • To improve dissolved oxygen availability, increase stirring speed, gas flow, or oxygen concentration in gas mixes (relevant for steel biorreactors).
    • Sophisticated management and control procedures are essential for varying parameters.
    • Cascades (individual parameter adjustments) are beneficial for adapting to certain applications.
    • The concentration of dissolved oxygen is pre-set in the controller. The first parameter (like stirrer speed) is adjusted within the defined range. If this doesn’t work, further changes to parameters are made until the target value is reached.

    Batch Process: End-of-Process Considerations

    • At the end of the batch, the biomass or media is harvested and processed to yield the desired product.
    • The bioreactor process is interrupted for cleaning and sterilization. Biomass is produced in stages.
    • A risk exists for increased substrate or product inhibition at high concentrations, which can drastically reduce yields.

    Batch Processes: Advantages and Disadvantages

    • Advantages*
    • Short duration
    • Less likely to become contaminated because no nutrients are added after the beginning.
    • Easy to manage
    • Traceability of batch material is easier.
    • Disadvantages*
    • Product is often mixed with nutrients, reagents, and cellular waste products and toxins.
    • Production time is shorter.
    • Batch storage may be necessary before further processing.

    Batch Process: Living Cell, Oxygen, and Carbon Source Correlations

    • The graph illustrates the relationship between living cell concentration, dissolved oxygen, and the limiting carbon source during operation.
    • Initially, there's a lag phase with slow cell growth.
    • Oxygen and carbon source consumption increases during exponential growth.
    • When the carbon source is used up, a stationary phase begins, progressing to a dead phase. The living cell count decreases significantly.

    Fed-Batch Processes

    • A partly open system that continually supplies nutrients during cultivation to prevent them from becoming limiting.
    • This method allows for higher overall product yield.
    • Microorganisms or cells follow an exponential growth pattern.
    • The substrate (e.g., sugar) is added periodically/continuously to the bioreactor. Feed rate optimization is essential.

    Fed-Batch Process: Additional Considerations

    • The substrate is pumped from a supply container to the culture vessel via a silicone tube.
    • Users can manually adjust feed times (linear/exponential/pulse-wise) based on conditions. Common conditions for adding nutrients include reaching a certain biomass concentration or running out of a specific nutrient.

    Fed-Batch Processes: Advantages and Disadvantages

    • Advantages*
    • Extends the productive duration of the culture.
    • Switching genes on and off is possible.
    • Optimizing productivity is achievable with different feeding strategies.
    • Disadvantages*
    • Increased time to process.
    • Build-up of inhibitory agents/toxins.
    • Increased contamination risk with more points of ingress.
    • Issues with batch separability for downstream processes.

    Fed-batch Processes: Relationships and Schematic Illustration

    • A fed-batch procedure relies on continuous substrate addition to increase exponentially while the cell concentration, dissolved oxygen, and limiting carbon source increase or fluctuate over time.
    • A sufficient feed rate of limiting components, promptly after the growth rate has achieved an exponential state, prevents the carbon source from running out.

    Continuous Culture

    • A steady state is established after a batch phase is completed.
    • Medium is added and harvested at the same rate (chemostat).
    • Ideal for conditions where an excess of nutrients, for example, could lead to toxin accumulation or excessive heating that in turn inhibits further growth.

    Continuous Culture: Additional Considerations

    • Cell density (turbidity) can be monitored to control addition/removal of liquid.
    • In perfusion, cells are either retained in the bioreactor or recycled.
    • Fresh medium replenishes and the cell-free supernatant is removed at the same rate.

    Continuous Culture: Advantages and Disadvantages

    • Advantages*
    • High productivity rates.
    • Efficient cleaning, sterilization, and handling.
    • Suitable for long-term, steady-state metabolic studies.
    • Disadvantages*
    • Difficult to maintain consistent cell density.
    • This method often takes a long time to produce the desired product.
    • Sub-batches of product can be difficult to separate, and there's an increased risk for contamination and genetic changes.

    Repeated Fed-Batch/Semi-Continuous Culture

    • A hybrid technique combining aspects of batch and continuous cultivation.
    • Leftover cells from a fed-batch are used as an inoculant for the next batch.
    • This feeding approach narrows the gap between fed-batch and continuous techniques.
    • This strategy is beneficial for many large-scale pharmaceutical and manufacturing environments. It is particularly useful for SCP production and applications related to lipids, fatty acids, and penicillin.

    Repeated Fed-Batch/Semi-Continuous Culture: Additional Considerations

    • A significant portion of the bioreactor volume is replaced with fresh media/substrate after a batch period.
    • The remaining cells serve as an inoculum for the subsequent batch.
    • Typically, this cyclical process is repeated over several days until the procedure is finished.
    • The time frame for this depends on growth rate and substrate utilization.

    Repeated Fed-Batch/Semi-Continuous Culture: Advantages over Fed-Batch

    • Potential for less toxin/unwanted metabolite build-up.
    • Preventing issues that could occur at high biomass levels, such as oxygen transfer/cooling capacity issues.
    • Protein/biomass yield remains consistent over process cycles.

    Repeated Fed-Batch/Semi-Continuous Culture: Advantages over Fully Continuous Culture.

    • Separation into sub-batches by time is possible, leading to better quality control and troubleshooting.
    • Processing time is closer to fed-batch cycles and not weeks or months, as in fully continuous cultures.

    Summary

    • Different cultivation methods (batch, fed-batch, continuous) allow manipulation of organism growth in bioreactors.
    • Controlling feed addition is key for sensitive and effective production.
    • Choosing the right strategy depends on the specific cultivation goals.

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    Lecture 03-Batch, Continuous, and Fed-Batch Processes PDF

    Description

    Explore the different types of microbial processes including batch, continuous, and fed-batch methods. Understand the importance of substrates and how each process impacts biomass and product yield. This quiz will enhance your knowledge on optimizing bioprocess conditions.

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