Introduction:
Upstream Processing (USP) involves all the steps leading up to the production of a target product in a bioprocess.
It primarily focuses on the cultivation of microorganisms or cells to produce valuable biomolecules such as proteins, vaccines, enzymes, and biofuels.
This phase is crucial because the quality and yield of the final product depend on the efficiency of upstream processes.
Stages of Upstream Processing:
Selection of Organism/Cell Line
Objective: Choose the best strain or cell line for producing the target product.
Examples: Bacteria (e.g., E. coli), yeast (e.g., Saccharomyces cerevisiae), fungi, or mammalian cells.
Considerations:
Genetic stability
Growth rate
Product yield and quality
Media Formulation
Objective: Prepare nutrient-rich media to support cell growth and product formation.
Components:
Carbon source (e.g., glucose)
Nitrogen source (e.g., ammonium salts, peptone)
Vitamins and minerals
Growth factors (for mammalian cells)
Optimization: Tailor media composition to maximize cell growth and product yield.
Inoculum Development
Objective: Produce a starter culture for large-scale fermentation.
Steps:
Preparation of Stock Culture: Maintaining a pure and viable culture.
Pre-culture/Seed Culture: Small-scale culture grown to a specific cell density.
Scale-up: Gradually increase culture volume through several steps to ensure healthy, active cells for the main bioreactor.
Sterilization
Objective: Eliminate contaminants to prevent unwanted microbial growth.
Methods:
Media Sterilization: Autoclaving or filtration.
Air Sterilization: HEPA filters in bioreactors.
Equipment Sterilization: Using steam or chemical agents
Fermentation/Bioreactor Operation
Objective: Cultivate cells or microorganisms under controlled conditions to produce the desired product.
Types of Fermentation:
Batch Fermentation: All nutrients added at the beginning.
Fed-Batch Fermentation: Nutrients added gradually during the process.
Continuous Fermentation: Fresh media continuously added while culture is removed at the same rate.
Control Parameters:
Temperature
pH
Dissolved oxygen (DO)
Agitation and aeration
Monitoring and Control
Objective: Ensure optimal growth conditions and product formation.
Parameters Monitored:
Cell density and viability
Nutrient concentration
Product concentration
Metabolite levels (e.g., lactic acid, ethanol)
Automation: Modern bioreactors use sensors and automated systems for real-time monitoring and adjustments.
Conclusion:
Upstream processing is a critical phase in bioprocessing, encompassing the preparation and cultivation of cells or microorganisms to produce a target product.
Efficient upstream processing ensures high yields and quality, laying the foundation for successful downstream processing and product recovery.