Lec 4/5/6 - Industrial Fermentation Systems Flashcards
Give the 5 parameters that the performance of a bioreactor depends on
- pH
- aeration
- O2 transfer
- foam reduction
- temperature
Describe the 2 types of metabolite that can form.
- primary -> production of metabolite during exponential phase (ethanol)
- secondary -> metabolite production @ end of growth phase (penicillin)
Give the 5 major products of industrial fermentors
- antibiotics - penicillin
- chemicals - ethanol (biofuel)
- nutritional additives - amino acids
- alcoholic beverages
- enzymes (proteases)
In terms of strain selection, give the key characteristics that an organism will have
- amenable to bioreactor conditions
- metabolic diversity
- ability to grow on a wide range of nutrients
- survive under range of conditions
- low toxicity/pathogenicity
- small size & high Sa:v for high rate of nutrient transfer and metabolism
What is the bonus that strains may have that makes it easier to extract the required compound?
secrete the component into the medium
What does screening of the organism involve?
- identifying product of interest
- isolation of known organisms from pre collected cultures or isolating organisms from environmental samples through batch/chemostat enrichment techniques
- isolation of microbe & looking @ level of activity
What are the 2 classes of strain development?
- genetic approaches - spontaneous mutations in population/inducing mutations. genetic engineering eg CRISPR can also be used to modify
- nutritional / physiological approaches - altering nutrients available, pH, O2 supply
Describe how we got to the yield of penicillin we see today using fermentors?
What is a rough value of this yield?
- 50g /l
- repeated mutations (Xray, UV, N mustard) applied to increase the efficiency of Penicillium crysogenum to make penicillin
- the techniques of fermetation we see today then allowed us to reach the final yield (started off around 60mg /l)
What is the most common reactor format in use today?
CSTR - conventional stirred tank reactor
Give some key features of a CSTR.
- cooling jacket to ensure system doesn’t overheat
- steam inlets for sterilisation
- air is filtered -> sterile
- pH monitored & acid/base reservoirs allow optimal conditions to be met
- propellers for aeration
- O2 and temp can also be controlled
The key objective in bioreactor performance is an optimal _____ production combined with high _____ of _____ utilisation
yield
efficiency
substrate
What are the key chemical and physical parameters that need to be controlled in bioreactors?
chemical
- pH
- nutritional type, levels
- limiting nutrient concn - eg producing N storage molecules therefore need to have low N concn
physical
- O2 supply/mass transfer - utilise microbubbles to deliver O2, also need to remove CO2
- aeration - levels of shear. levels of aeration can’t be too high or else cells will burst
- heat transfer
Process formats vary depending on the product:
What are the 2 ways of getting primary metabolites?
Give some pros/cons of each
- single fermentation in CSTR - cons: have to remove whole culture medium and resterilise EVERYTHING
- fed batch culture - 2/3rds of medium removed periodically and fresh medium pumped in. pros: dont have to resterilise, overall greater production of product
What are the 2 ways of obtaining 2ndry metabolites?
- fed batch culture - initial stages aimed @ cell growth and division. addition of nutrient designed to slow/inhibit growth and lead to production of 2ndry metabolite
- 2 vessel system. first continuous vessel - aimed @ producing biomass. can then seed a no. batch cultures. 2nd vessel = batch culture aimed @ producing 2ndry metabolite (w/ low or no growth)
How is penicillin made - what organism makes it and what type of process?
Penicillium chrysogenum
Fed batch process
Describe the process & stages of making penicillin - from first inoculations to extraction
Medium inoculated w/ freeze-dried spores in small fermenter initially
transferred to 2 successively larger fermenters to create a larger inoculum for the production phase
production phase (120-200hrs) - high O2 supply maintained & C/N consistently supplied to get high yield
extraction. penicillin excreted in the medium and extracted at the end of fermentation
