The correct answer is Option (4) - Increase the area for oxygen transfer

Bioreactors serve as large vessels designed for the large-scale cultivation of cells to produce specific gene products for commercial purposes. Small volume cultures cannot yield appreciable quantities of products. To produce in large quantities, the development of bioreactors, where large volumes (100-1000 litres) of culture can be processed, was required.

These bioreactors create an optimal environment for cell growth, regulating factors such as temperature, pH, nutrient availability, and oxygen (for aerobic bioreactors), to support the production of the desired gene product.

One widely used type of bioreactor is the stirred tank bioreactor, which is engineered to ensure thorough mixing of the culture medium. There are two main categories of stirred tank bioreactors: simple stirred-tank bioreactors and sparged stirred-tank bioreactors.

A sparged tank bioreactor is specifically designed for aerobic processes and stands out for its enhanced surface area available for aerating the culture medium. This extended surface area allows air to form bubbles above the liquid culture, and these bubbles disperse throughout the culture, a phenomenon known as gas entrainment. Sterile bubbles are also introduced into the culture medium for aeration, further increasing the surface area available for efficient oxygen transfer. This facilitates the diffusion of oxygen into the culture, supporting the growth and productivity of the cells within.