Question

can someone outline in detail the factours affecting growth in a bioreactor and how to control them e.g pH,temperature,dissolved oxygen

Answer 1

Ans : Bioreactor is any manufactured device or system that supports a biologically active environment.In one case, a bioreactor is a vessel in which a chemical process carried out which involves organisms or biochemically active substances derived from such organisms.The process can either be aerobic or anaerobic.These bioreactors are commonly cylindrical,ranging in size from litres to cubic metres and made up of stainless steel.A device is designed to grow cells or tissues in cell culture.

There are certain factors which affects growth of that cells or tissues which are PH, temperature,dissolved oxygen. Increasing temperature inversely affects both the volumetric mass transfer coefficient and oxygen solubility in culture medium.Oxygen solubility in pure water falls with increasing temperature.Dissolved oxygen is important factor affecting growth of cells or tissues in the cell culture.Oxygen is the key substrate for growth ,production and maintenance of activities.Cells obtain their oxygen in free and noncompound form ,called dissolved oxygen (DO).One important function of the bioreactor is providing dissolved oxygen to cells continuously through a process called aeration.

Aeration in the bioreactor typically occurs when, Oxygen diffuses through overlay to the cell culture medium interface and oxygen from spargers dissolves in cell culture with the help of agitation. Agitation disperses the oxygen bubbles and promotes mass transfer of the gas bubbles through gas-liquid interface. The rate of oxygen transfer (OTR) from gas to liquid interface is a function of physicochemical properties of the cell culture medium. Ph is also affecting growth of cells or tissues ,it leads to oxidative cellular damage of the cell culture media.

It is necessary to control that above factors affecting cell culture growth. Controlling PH in the bioreactor is critical  to successful manufacturing.Most culture needs to be maintained in a specific narrow range of PH for maximum productivity.Typical PH range is 7.0+ 1.0 .PH can be controlled by controlling various factors and through use of buffers,the addition of base solution and sparging of nitrogen.

Temperature of the fermentation medium is maintained by cooling jackets,coils or both. Particularly exothermic fermentations may require the use of external heat exchangers. Dissolved oxygen level can be controlled by adjusting the agitation speed and aeration rate remarkably .