Question 1

What are the main components of a growth medium for bioreactors?

Accepted Answer

A typical growth medium contains carbon sources like glucose or glycerol for energy and biomass building blocks, nitrogen sources such as ammonium salts or yeast extract for proteins and nucleic acids, mineral salts for pH buffering and phosphorus, vitamins, trace elements, and water. Each component plays a specific role in supporting microbial growth and product yield.

Question 2

Why is pH regulation critical in bioreactor growth media?

Accepted Answer

Optimal pH ensures enzyme activity and cell viability throughout the culture process. Salts containing phosphate function as pH buffers, maintaining stable conditions. Improper pH can impair growth, reduce product yields, and compromise the metabolic functions essential for producing enzymes, antibiotics, and biomass.

Question 3

What role do trace elements play in bioreactor media?

Accepted Answer

Trace elements like iron, magnesium, zinc, and copper are required in minute quantities to support enzymatic catalysis, redox balance, and structural stability of biomolecules. These micronutrients are essential for optimal cell function and product formation, though their absence or excess can limit growth and reduce yields.

Question 4

How does oxygen supply differ from other medium components in aerobic cultures?

Accepted Answer

Oxygen is not added as a chemical component of the medium. Instead, it is supplied through sparging and mechanical agitation in the bioreactor design and operational system. This physical introduction ensures adequate gas transfer, which is often a limiting factor in high-density cultures.

Question 5

What is the difference between defined and complex growth media?

Accepted Answer

Defined media have a known, synthetic composition with precisely measured ingredients, while complex media contain ingredients of variable composition like yeast extract. The choice depends on the specific microbial strain and desired product. Formulating suitable media often involves empirical testing or methods of medium optimization to tailor the nutrient profile.

Question 6

How do selective agents function in specialized bioreactor media?

Accepted Answer

Selective agents or inhibitors suppress the growth of unwanted microorganisms or enrich specific target organisms. In lab-scale processes, antibiotics may be added as selection pressure to ensure survival of only resistant cells. This approach helps maintain culture purity and directs metabolic resources toward desired product formation.

Question 7

Why must all medium components be balanced in bioreactor design?

Accepted Answer

Balancing all components prevents nutrient limitation or toxic excesses, both of which hamper growth and reduce product yield. Excess nutrients can inhibit cells, while deficiencies restrict biosynthesis and metabolism. Proper balance ensures optimal enzyme activity, cell viability, and efficient production of valuable products like enzymes, antibiotics, and biomass.

Designing Growth Media for Bioreactors