Question

discuss in detail rheology,flow rate and asepsis in relation to bioreactors

Answer 1

Ans. Rheology- It is the study of flow of matter in a liquid state and also as soft solids. It can be understood as the science of deformation and flow within a material.

In bio-processing, fluids contains suspended solids, which are present in more than one phase and also have non Newtonian properties. Bioreactors are the key equipment of biotechnology. Fermentation takes place in bioreactors. To produce a fluid flow in bio-processing, a shear force must be applied.

Non-Newtonian fluids are which do not obey the Newton's law of viscosity. Many fermentation processes involve materials such as extracellular polysaccharides, starch and culture broth which shows non-Newtonian behavior.

Asepsis- It means free from unwanted microorganisms. The purpose of asepsis is to eliminate infection. A bioreactor is used for fermentation for the production of living organisms like bacteria or yeast which are used in processes like manufacturing of drugs etc. Bioreactors provide optimal conditions (optimum temperature, pH, oxygen) to obtain the desired product.

There are three levels of asepsis- Sterilizing, disinfecting and cleaning.

In a bioreactor, asepsis can be achieved through integrated efforts on system design, effective validation, checks and maintenance, operating procedures by trained motivated personnel. A big problem in large scale bio-manufacturing is stopping contamination. The sterile boundaries of a bioreactor, the ways it can be breached and methods used for identifying the cause of contamination should be well known. The sterile boundary is maintained by-

1. Sterile filtering of gas flows

2. Sterile filtering of liquids in bioreactor

3. By maintaining a positive pressure inside the reactor

Modes of breaching the sterile boundary-

1. Port is not sterilized

2. Drainage failures

3. Cracks in the valves.

Identifying root cause-

1. Sudden drop in dissolved oxygen levels

2. Contaminant species identification

3. Valve temperature profile

4. Bioreactor maintenance history