On the 4th day of our fermentation experiment, we continued taking hourly samples and ran the process until 11 am. After 11 am, we started to close down the bioreactors and finish the experiment.
On that day, Mr. Shaman lectured us about finishing procedures, disposal techniques, preparing the fermenter and equipment for the next experiment and analyzing the data and results with computer and computer program; Iris. He also showed us how to shut down the fermenter, step by step.
The samples
This is how we did it:
Closedown and cleaning.
- Stop all the feeding or reagent addition, aeration, and stirring.
- Stop all the other functions from the control panel.
- Disconnect all tubings and connections between the vessel and the base unit.
- Unscrew the cover plate of the vessel.
- Lift the vessel from the base unit.
- Discharge the vessel to the drain (since the microorganism used was not phatogenic).
- Take off all tubings and equipment.
- Unscrew the top plate and lift it up.
- Wash the vessel and all the metal parts separately with some mild detergent.
- Let dry or wipe dry with tissue papers.
- Maintain and prepare all the parts and equipments for future usage. Store properly.
Discharging the vessel
After the closedown, we talked about the data and how to analyze it. We were shown how to use Iris in order to collect and handle the data and the results gained. Multiple parameters can be chosen and various styles used when we were handling the data. Always use the ones that fit the best on your purposes.
Observation:
OD 600 value and glucose reading.
L - Low value of glucose.
Graph Absorbance at OD600 vs time
From the data, we can conclude that as the time inccrease, the turbidity which is the number of cells is increasing. It is because the yeast is growing as their nutrient and condition still enough. We can see that from T1 until T21. But at T22, the OD value starts to decrease. This is due to the limited nutrient or substrate in the media. The yeast begin to starve and will undergo the stationary phase. For the glucose value, as time increase the glucose reading decreased. The yeast consumed glucose to grow. We cannot determine the value after T4 because we only use the diabetic test kit.
Graph:
Based on the graph, our group has longer lag phase than the other group. According to Mr Shaman, it is maybe because of our culture has less viable cell or maybe because we cultured the older cell. It is because by the time we inoculate the loop of cell from the colony on the Petri dish, we cannot see and determine which one is viable and new cell. So the cell might be different.
As we can see, the red line and blue line indicate the pO2 value and speed of stirrer respectively are complementing each other. pO2 is the parameter that determines the dissolve oxygen in the media. When pO2 start o decrease, the stirrer will increase their speed in other to overcome the depletion amount of oxygen dissolve.
According to Mr Shaman again, the pH of the culture in the vessel will increase after it is going down, it is because the cells are producing toxin or maybe it has been contaminated with other foreign microbe. That is why we need to do sampling and check it under microscope. The green line and yellow line indicate the antifoam and pH value respectively. This two parameters are complementary each other. As we can see when the antifoam was added to overcome the foaming problem, the pH starts to decrease. The antifoam contains 30% aqueous emulsion of silicon polymer. Lastly as the time of fermentation increase the temperature also increase. This is because the cells themselves produce heat.
the 3rd day
Monday, October 18, 2010
the 4th day @ 10:08 PM 
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