2. Fermentor was inoculated with 100mL of seed culture and fermentation was continued for 24 hours.
3. 10mL blank sample before inoculation and an hourly sample were taken
And... our tedious day beings...
Each members rotated shifts to take the hourly sample. In total, we have 12 samples which also included the blank sample.
They glow under the UV light !!!
Calculation of log(x/x0) value for graph of cell growth :
The above graph shows the accumulated amount of bacterial cells in the fermentor over 10 hours. The amount of the bacterial cells in the fermentor gradually increases every hour when the sample was taken. This shows that the cells were having sufficient nutrients and oxygen therefore growing normally.
However there was a slight decrease in the amount of bacterial cells at the 6th hour. This might be due to the high concentration of bacterial cells depleting the oxygen at a fast rate. As a result, amount of oxygen is insufficient in the fermentor and bacterial cells are not able to grow properly. However, after adapting to the environment, bacterial cells continue to grow again and this indicates that the cells are still in the exponential phase.
From the history plot, we can see the temperature values (red), stirring rate (teal), dissolved oxygen, PO2 values (green), and pH values (purple). It can be seen that, basically, the lines fluctuates a lot.
As cells grow, they use up the nutrients, oxygen etc. Heat will be produced due to metabolism; pH will be decreased due to carbon dioxide given off. The system needs to adjust the parameters constantly to ensure that the cells are growing in their optimum conditions. Therefore, fluctuations of the values of the different parameters were seen.
From the history plot, the temperature was maintained around the optimal temperature of 32ºC. Any fluctuation detected by the temperature probe by more than 0.5’C is automatically adjusted back to optimum level. The pH was also maintained within the desired values of 7.5.
The stirrer control and the pO2 control are the values that indicate the progress of the growth of the bacterial cells. As pO2 value decreases (due to increasing amount of bacterial cells), the stirrer speed increases in order to ensure an even and faster distribution of oxygen within the fermentor. This accounts for the high fluctuations of these two curves (pO2 and stir speed) as seen in the history plot.
However, the general trends of the parameters were stable. This meant that the system is working well and hard making the conditions optimal for cell growth.