Bioprocessing and Biomanufacturing

Primary metabolites are compounds produced directly from primary metabolic pathways and are essential for growth and development. Examples include amino acids, organic acids, and ethanol.

Secondary metabolites are produced by secondary metabolic pathways and are not directly required for basic growth, but they have important functions such as defence against pathogens and herbivores, tolerance to abiotic stress, and attraction of insects/animals for pollination or seed dispersal. Examples include antibiotics like penicillin, and plant products like taxol and shikonin.

The main challenges in developing a bioprocess were to increase the production of useful biological products like penicillin at a commercial scale. For this, the process had to be made systematic using the culture of the biological entity, and the help of microbial physiologists, life scientists, and technologists was needed.

Another challenge was that the products of living organisms are often produced in very small natural amounts, so they had to be produced in bulk quantities and in a purified form. This required the development of bioreactors/fermenters for large-scale culture and the establishment of bioprocessing, which combines biological systems with chemical engineering processes to obtain desired products at commercial level.

A bioreactor is an engineered vessel made of glass or steel that provides a biologically active, aseptic environment for culturing cells under suitable nutritional and environmental conditions. It is commonly cylindrical and is used for microbial, plant and animal cell cultures.

A typical bioreactor has these components and functions:
- Agitator shaft with impeller: mixes the contents and keeps cells uniformly suspended, improving nutrient and oxygen transport.
- Sparger: supplies sterilised air/oxygen continuously through microfilters.
- Baffle: breaks vortex formation and prevents unwanted spinning of the broth.
- Jacket: allows circulation of water at a desired temperature to maintain optimum temperature.
- Temperature and pH probes: sense process conditions.
- Digital controller: monitors and controls parameters like temperature, pH, and stirring speed.

Its application is to provide the optimum conditions for growth and product formation during industrial bioprocessing.

A bioprocess has two main operational stages:

1. Upstream processing
- optimisation of nutritional conditions in media
- sterilisation of media, bioreactor and equipment
- production of pure, active inoculum
- optimisation of environmental conditions for growth and product formation

2. Downstream processing
- extraction, recovery and purification of the product
- disposal of effluents produced during the process

So the concept map is:

Raw material/medium preparation → sterilisation → inoculum development → culture growth in bioreactor (upstream) → product recovery → purification → effluent disposal (downstream).

(a) Upstream processing: It includes the preparatory steps before product recovery. These are formulation of nutrient media, sterilisation of media and equipment, production of healthy inoculum, and optimisation of conditions such as temperature, pH, aeration and agitation for growth and product formation.

(b) Downstream processing: It includes the steps after fermentation for obtaining the product in usable form. These are extraction, recovery and purification of the product, followed by disposal of effluents produced by the process.