Bioreactor System: Instrumentation and Control

An apparatus for growing organisms (yeast, bacteria, or animal cells) under controlled conditions. used In industrial processes to produce pharmaceuticals, vaccines, or antibodies. Also used to convert raw materials into useful byproducts such as in the bioconversion of corn into ethanol. Bioreactors supply a homogeneous (same throughout) environment by constantly stirring the contents. Bioreactors give the cells a controlled environment by ensuring the same temperature, pH, and oxygen levels.

Types of Bioreactors Batch: Media and cells are added to the reactor and It Is run until a predetermined set point (I. e. time, concentration). The bioreactor has a constant volume (the Initial volume). Fed-Batch: The bioreactor Is a batch process In the beginning and after a certain point a feed Input Is Introduced and the volume of the vessel Increases. Continuous: The bioreactor starts with an initial volume and media is constantly introduced and product is constantly taken out. The inputs and outputs are at the same rate, so the volume always remains the same.

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Bioreactor Components Agitator An agitator Is required to mix the contents In the vessel to ensure a homogeneous environment. Agitators consist ofa shaft and Impellers. Mixing of the bioreactor Is crucial In order to supply nutrients and oxygen to the culture and to maintain a constant pH and temperature. Sparger The sparger is an apparatus used to introduce gasses into the vessel. Spargers are located at the bottom of the vessel and consist of a tube with tiny holes for the gas to escape through Into the culture.

The gas coming out of the sparger helps to erate and mix the contents in the vessel, as well as supply oxygen to the cells. Baffles Baffles are obstructions on the side of the vessel that generate turbulence In the flow of the culture. Baffles are made out of stainless steel and are welded to the inside of the vessel. Baffles help to mix the culture by creating a more turbulent flow. Probes Bioreactors require probes to monitor the culture in the vessel. The probes are found at different locations on the vessel: head plate, top probe belt, bottom probe belt.

Useful probes include temperature, pH, DO (dissolved oxygen), and C02 Cooling Jacket Cells give off heat when growing and dividing. To maintain a constant temperature in the reactor, the vessel is covered by a cooling Jacket. Coolant (cold water or glycol) flows through the cooling Jacket to regulate the temperature. The temperature is controlled by the flow rate of the coolant. Ports Bioreactors require addition ports, where material is either introduced or removed from the vessel. Ports are needed to add the media (media port), cells (inoculation ort), and nutrients (feed ports).

Ports are also used for the addition of acid and base for pH control. A sample port is also located on each vessel to remove culture for off-line investigation Condenser A condenser is an apparatus that captures saturated air leaving the vessel. The condenser is cooler than the saturated air allowing it to condense on the surface and return to the vessel as a liquid. Condensers help to minimize the loss of material out of the reactor due to evaporation. Filters Bioreactors need inlet filters to ensure the gasses entering the vessel are sterile.

They require exhaust filters to keep the reactor sterile and allow gas to escape to regulate pressure. Filters require filter housing – a stainless steel cabinet to hold and sterilize the filter. Valves Valves are used at many different locations on the bioreactor – Sample valve – where a sample from the bioreactor can be obtained. – Harvest valve – location where the tank can be drained for harvest. -Ports – contain an automatic steam lock valve, so liquid can be added to the vessel (the port can be sterilized after use to prevent contamination)