3&4. Bioprocesses Flashcards
Bioprocess
Any process that uses the growth of complete living cells or their components to obtain desired products
Industrial fermentation
Any process that uses microorganisms at a large scale in an industrial setting
Fermentor (bioreactor)
Machine that processes organic matter into biomass, which can be used as fuel in a Bio Gas engine or Bio Generator
Upstream processing
All the steps in a fermentation process starting from coming up with the idea to obtaining the raw (unpurified) product
Downstream processing
All the steps in a fermentation process starting from purifying the product to commercialization
Seed stock
The original stock from which we obtain all the microorganisms we use in a fermentation process
Work strains
Duplicates of the seed stock that we use in day to day work
Components of a fermentation medium
Water
Carbon source
Macronutrients
Micronutrients
Growth factors (if the microbe requires it)
Optional: anti-foaming agents, metabolic precursors, virus inhibitors
Feedstock
Substrates that we use to provide nutrients to the fermentation medium
How do we choose a carbon source for the fermentation medium?
We use the cheapest option that our target microorganism can use
Types of carbon sources
Glucose, sucrose
Lactose
Starch
Cellulose
Vegetable oils
Ethanol
How do we balance the pH after adding nitrogen sources (they’re usually basic)?
We add buffers
Sodium biphosphate or monopotassium phosphate
Fermentation “modes”
The way we add nutrients to the medium
1. Batch
2. Continuous
3. Fed-batch
Batch mode
We use only the fermentation medium we started with, we do not add anything
Continuous mode
We continuously add sterile medium to the tank and remove the product
Fed-batch mode
We intermittently add nutrients to the fermentation medium in order to avoid nutrient deficiency and catabolite repression
Catabolite repression
If we add too much glucose initally, that will be the only carbon source that the microbes use, greatly diminishing the productivity of the fermentation
Phases of microbial growth
Lag phase: population is not growing yet
Exponential phase: primary metabolites are produced
Stationary phase (idiophase): secondary metabolites are produced as population plateaus
Death
Primary metabolites
Essential for the continued growth of the microbe (amino acids, nucleotides…)
Secondary metabolites
Non-essential for growth (antibiotics)
If you want to improve antibiotic synthesis, what mode would you use and how?
Fed-batch
Add the limiting nutrient during idiophase (usually glucose)
Mesophiles
Grow between 20-40 C
E coli and saccharomyces
Thermophiles
Grow at between 45-65 C
Psychotrophs
Grow at 0-15 C
Downstream processing steps for an intracellular product
Cell-medium separation
Cell concentration
Cell lysis
Extraction
Purification
Downstream processing steps for an extracellular product
Cell-medium separation
Extraction
Purification
Common methods for cell-medium separation
Centrifugation
Sedimentation
Ultrafiltration
Coagulation/flocculation
Coagulation (as a cell-medium separation method)
Same as sedimentation, but a coagulant is added to cause cells to aggregate, making the process faster
Ultrafiltration
0,2 micrometer filters that separate cells and medium
Methods for cell disruption (lysis)
Pressure
Sonication
Enzymatic
Pressure (as a cell-lysis method)
Create an environment of high pressure and suddenly release it. Cells are resistant to increases in pressure, but not so much decreases in pressure. The sudden release will cause them to rupture from expanding too quickly
Methods for product extraction
Extraction with organic solvents
Precipitation with ammonium sulfate
Methods for product purification
Electrophoresis
Isoelectric focusing
Chromatography
