Which of the following statements is incorrect?

To determine which statement is incorrect, let us analyze the purpose, structure, and operation of bioreactors step-by-step:

1. What is a bioreactor?
A bioreactor is a vessel or container in which raw materials are biologically converted into specific products, individual enzymes, or cells, using microbial, plant, animal, or human cells.

2. Scale of production:
Bioreactors are designed for the large-scale production of biomass or biological products (typically processing volumes of 100 to 1000 liters or more). Small-scale bacterial cultures are typically grown in laboratory flasks or test tubes, not in bioreactors. Therefore, stating that bioreactors are used to produce small-scale bacterial cultures is incorrect.

3. Growth conditions:
A bioreactor provides optimal growth conditions such as temperature, pH, substrate concentration, salts, vitamins, and oxygen levels to achieve the desired product. This makes the statement "A bio-reactor provides optimal growth conditions for achieving the desired product" correct.

4. Stirring type bioreactors:
The most commonly used bioreactors are of the stirring type (stirred-tank bioreactors). They ensure even mixing and oxygen availability throughout the reactor. Thus, the statement "Most commonly used bio-reactors are of stirring type" is correct.

5. Control systems in a bioreactor:
A bioreactor typically consists of an agitator system (for mixing), an oxygen delivery system, a foam control system, a temperature control system, a pH control system, and sampling ports. Thus, the statement "Bio-reactors have an agitator system, an oxygen delivery system and foam control system" is correct.

Based on the analysis, the incorrect statement is: "Bio-reactors are used to produce small scale bacterial cultures".