Part 2: Deep Tank Fermentation Flashcards
What was corn steep liquor? Describe the process where it produced from.
A waste product from ‘corn wet milling’ process. Clean corn is soaked in water containing lactic acid and sulfur dioxide (stops it from fermenting) for ~40hours. Liquor is filtered then concentrated using evaporators.
Why is corn steep liquor effective? What was its key use?
Liquor used to steep the corn is full of nutrients like amino acids, nitrogen and carbon, minerals and vitamins. These helped increase the yields of penicillin massively. Key use is as fermentation media for antibiotic production.
Prior to the 1940s, what was the bulk of Britain’s experience in fermentation?
Production of beer. Samuel Allsopp and sons was one of the largest brewery company in Burton on Trent.
What were fermentors made from before 1940s?
Open-topped wooden vessels
Why was using open-topped wooden vessels naive engineering? How did it succeed despite being a bad process?
Wood is hard to clean, any organisms in the air could spoil the process. It worked so well because of so much yeast put in the system, it outgrew any other microorgaism.
Describe how Yorkshire created beer.
‘Yorkshire Squares’. Tank with tray on top. Yeast from on top in the tray. recirculate the trays, places it back on the bottom so beer can keep being made. Open system, made of concrete, easy to clean, simple technology
What contribution did Louis Pasteur have to the brewing industry?
invented a fermentor that could be sterilised and run a pure culture in 1876. A sealed vessel with the ability to let off gas. Brewing industry were not interested.
How did WWI influence fermentation industry?
Acetone was needed to produce cordite used in artillery shells.
What process develops acetone? Who developed the process? What bacteria is fermented in the process?
ABE process. Produces acetone, butane and ethanol. Chaim Weizmann developed the process. Clostridia bacteria is fermented under aerobic conditions.
Describe the ABE process
Simple tech, no aeration needed. Corn was milled. Germ and bran were extracted before the addition of hot water. Corn mash was inoculated for 2 days with clostridia added. distillation used to harvest products.
What was recovered from distillation in ABE process?
50% water, 30% Butanol, 15% acetone, 15% ethanol. These were tranferred to kettle stills to produce pure butanol, acetone, ethanol. 3:6:1 ratio ABE.
What was the issue with Pfizer’s aerated fermentation tanks with producing antibiotics? How was the issue resolved?
Bubbling sterile air through the mixture caused severe foaming. Squibb, another pharmecuetical company solved this issue by introducing anti-foam. It altered the surface tension and popped the bubbles.
What 7 factors play part in reactor design?
Materials, shape, sparger, impellers, baffles, mixing profile, air supply.
List some materials used for reactors. State some of the considerations involved.
wood, concrete, slate, pastic, glass, ceramic, metal (copper, bronze, steel, stainless steel).
considerations: cost, durability, ease of use, compatibility with the process, shedding of contaminants, can it be sterilised, how easy is it to clean
Discuss the shapes used for reactors, any drawbacks/advantages to them
Square (corners are very hard to clean), cylindrical with flat ends (preferred), cylindrical with domed edges (expensive but easier to clean).
Discuss considerations for air supply to a bioreactor
Air supply must be sterile. Air filters were metal cylinders with glass wool, now made out of polymers with different pore sizes.
What is the purpose of a sparger?
Transfers oxygen/air into the reactor.
What is the mass transfer of bubble a function of?
The surface area of a bubble. Small bubbles=large SA=good MT
What is the purpose of baffles?
Prevent vortexes in the reactor.
What is the purpose of impellers?
increases shear. If it hits a bubble, it will ‘shear’, reduce its size, good as SA increases, so MT increases.
Name the 6 different types of impellers? Which one is most appropriate for bioreactors?
Propeller, anchor, gate anchor, helical screw, pitched blade turbine (used for axial flow), six-flat blade disc turbine.
propellors and six-flat blade disc turbine.
Give an example of a flat blade design
Rushton turbine –> flat blades so introduce shear
What impeller is appropriate for mammalian cells?
Mammalian cells are sensitive to shear. You don’t want a shear environment. Pitched blade turbine (axial flow impellor) that allows for axial flow is appropriate.
