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Task 1

Mammalian cells require specific environmental parameters to grow effectively in a bioreactor.

Oxygen is essential for cellular respiration and cell division. Maintaining dissolved oxygen (DO) levels between 30% to 40% is crucial; while adequate oxygen supports cell growth, excessive levels can lead to reactive oxygen species that may chemically degrade the protein of interest.

Carbon dioxide is a waste byproduct of glucose metabolism, cell growth, and protein production. Elevated CO2 levels above 20% can have detrimental effects on cell growth and protein production. Therefore, optimal dissolved carbon dioxide concentrations should be maintained between 5% to 10%.

Both DO and CO2 levels impact the pH of the media and product quality. It is important to control these gas levels to ensure optimal conditions for cell growth and to prevent adverse effects on protein production.

Task 2

Dissolved Oxygen Probe: Utilizes polar graphic electrodes to relay the dissolved oxygen concentration to the bioreactor controller.

Optical Sensors: Utilizes fiber optics to monitor the DO probes.

CO2 Probes: Utilizes pH probe technology by surrounding the pH probe with a bicarbonate solution that is separated from the media via a hydrophobic membrane. The membrane allows CO2 to diffuse across it and into the bicarbonate solution, relaying the CO2 levels to the bioreactor controller. In commercial production, CO2 levels are usually measured by off-gas analysis.

Calibration and maintenance are required to preserve the functional integrity of these instruments.

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Task 1

Mammalian cells require tightly controlled environmental condition to grow and thrive in a bioreactor. One crucial aspect is oxygen supply, typically provided through sparging, where air or oxygen is introduced into the culture medium as bubbles. The interfacial area and the residence time are critical for efficient oxygen transfer to cells. Smaller bubble has a larger surface area / interfacial area which allows oxygen to dissolve more easily and quickly into the culture media and a longer residence time compared to larger bubble. This may create shear stress which may damage sensitive mammalian cells. Overall, sparging parameters must be optimized to balance oxygen delivery while minimizing stress on cells

Task 2

Ring Sparger: Introduces air or oxygen into the culture medium. The small perforations generate bubbles to facilitate oxygen transfer, supporting cell respiration. Proper sparger design ensures even distribution and avoids oxygen depletion zones.

impeller: Positioned relative to the sparger, it ensures effective mixing of oxygen and nutrients throughout the bioreactor.

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xiao hui (impact of impeller in bioreactor)

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xiao hui (impact of impeller in bioreactor)

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Task 1

Impeller is an essential environmental parameter as it was suited in the middle of the bioreactor. It responsible for mixing nutrients, oxygen, heat into the media so that the cells have access to the contents in the media. Impellers are crucial of inducing shear stress; it cannot turn too fast as higher shear stress is produce and damage mammalian cells. The impact of impeller could affect foaming too, as the impeller stirs at a higher rpm than the setpoint rpm, it could generate foam which inhibits oxygen transfer to the cells affecting oxygen uptake rate.

Task 2

Axial flow that generates low shearing which is suitable for mammalian cell culture. The axial flow impeller was designed to have angled blades that promote top to bottom rotation, this allows homogenous mixing of contents and cells.

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The 10 steps of bioreactor assembly (Teja) 

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The 10 steps of bioreactor assembly (Teja) 

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Task 2

The video is talking about stetting up the Mini Force 2 bioreactor is quick and easy, with all necessary components provided for a first run in just 10 minutes.

Vessel: There should not be gaps between the tempering block and the glass vessel. Water is filled up to 2/3 into vessel for sensor test. Vessel can be composed of glass or stainless steel which allows cells to proliferate within the tank in an agitated suspension.

Bottles: Water is filled into the bottle for pump test.

Tubing & Cables: Pre-installed tubings for the gas inlet and tubings for the exit gas cooler. Gas tubing is connected with sterile filter.

Sensors: Dissolved oxygen sensor, Temperature sensor and Antifoam sensor are installed inside the vessel. DO sensor helps to monitor oxygen levels in cell culture media to ensure proper cell growth and metabolism. Temperature sensor reads the actual process value of the culture medium. Antifoam reduces the formation of foam.

Super safe sampler: It allows researchers to withdraw tiniest samples without losing any culture liquid.

O rings: Place the O rings when installing the sensors. O rings help to create a seal between two or more parts and prevent leakage of fluids/gases.

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Task 1:

To optimize cell culture, mammalian cells require optimal pH so as to thrive within the bioreactor. Common interrelated cell culture conditions that affect pH are temperature, cell growth, lactic acid and CO2 levels. It is difficult to maintain the pH within the cell culture as the mammalian cells produce many products that may affect the pH of the cell culture itself. As lactic acid and CO2 are constantly produced, it will cause a decrease in pH. Buffering components in the media therefore help stabilize pH. Addition of a base solution may also be used to help stabilize. If there is high cell density, sparging of N2 gas can be sued to strip the media of dissolved CO2, bringing it up to be vented out of the bioreactor. Certain factors used for controlling pH to be looked out for are media buffering capacity, cell growth and cell density, sparging and mixing of gases and build-up and utilization of lactate.

Task 2:

pH Probe/Sensor:

A critical part of the bioreactor, the pH probe continuously monitors the pH of the culture medium. It provides real-time feedback to the control system.

Acid and Base Addition System:

To stabilize the pH, the bioreactor is equipped with pumps or valves that add acid (e.g., HCl) or base (e.g., NaOH) to the medium based on the pH readings. This process ensures the pH remains within the desired range for optimal growth or production.

Controller:

A PID (Proportional-Integral-Derivative) controller or a similar system is used to automatically adjust the addition of acid or base based on pH fluctuations. The controller uses feedback from the pH probe to calculate and execute the required adjustment.

Buffer Systems in the Medium:

While not a mechanical component, buffers in the growth medium (e.g., phosphate, bicarbonate) help resist pH changes caused by metabolic activities of the organisms.