Question

Explain Stirred-tank Reactor.

Hint:

Stirred-tank reactor = mixing + aeration = uniform environment for microbial growth and product yield.

Answer 1

Step 1: Definition.
A Stirred-tank Reactor (STR) is a common type of bioreactor used in industrial microbiology and biotechnology for large-scale production of microbial products, enzymes, antibiotics, and recombinant proteins.

Step 2: Structure.
\[\begin{array}{rl} \bullet & \text{It is a cylindrical vessel made of stainless steel.} \\ \bullet & \text{Equipped with:} \\ \bullet & \text{Agitator (impeller): Provides mixing of culture medium.} \\ \bullet & \text{Sparger: Supplies sterile air (oxygen).} \\ \bullet & \text{Baffles: Prevent vortex formation and improve aeration.} \\ \bullet & \text{Cooling jacket: Maintains optimum temperature.} \\ \end{array}\] \end{itemize}

Step 3: Working.
\[\begin{array}{rl} \bullet & \text{Microbes are inoculated in nutrient medium inside the reactor.} \\ \bullet & \text{Continuous stirring ensures uniform distribution of nutrients and oxygen.} \\ \bullet & \text{Waste gases are released through an outlet, while product is harvested from the vessel.} \\ \end{array}\]

Step 4: Applications.
\[\begin{array}{rl} \bullet & \text{Production of antibiotics (penicillin, streptomycin).} \\ \bullet & \text{Production of alcohols, enzymes, vaccines, recombinant proteins (like insulin).} \\ \end{array}\]