Strawberry Flavored Activia Dilutions
Today I conducted a lab using strawberry flavored Activia yogurt. This was done to see how much bacteria is contained in the specific yogurt. Results are posted below.
Objective: Discover how much bacteria is in Strawberry flavored Activia yogurt. The yogurt was diluted at 104 x and 105x.
Method:
1. Set up materials. Label test tubes and plates.
2. Put 1.8 mL of LB media into each test tube.
3. Put 200 μL of yogurt into first tube (10x).
4. Shake 10x. Take 100 μL from 10X and pace into next test tube (102x).
5. Repeat steps 3+4 until dilution factor of 10^4.
6. Plate 100 μL of 104 x 3 times.
7. Spread each plate and put into incubator for 48 hours or more.
8. Repeat steps 1-7 for dilution factor of 105 x.
9. Count colonies and calculate CFU.
1. Set up materials. Label test tubes and plates.
2. Put 1.8 mL of LB media into each test tube.
3. Put 200 μL of yogurt into first tube (10x).
4. Shake 10x. Take 100 μL from 10X and pace into next test tube (102x).
5. Repeat steps 3+4 until dilution factor of 10^4.
6. Plate 100 μL of 104 x 3 times.
7. Spread each plate and put into incubator for 48 hours or more.
8. Repeat steps 1-7 for dilution factor of 105 x.
9. Count colonies and calculate CFU.
Results:
104 x
Plate
|
Number of Colonies
|
A
|
15
|
B
|
34
|
C
|
12
|
Average:
15+34+12= 61
61/3= 20.3
CFU:
20.3 x 104/ 0.1= 2.03 x 106
105 x
Plate:
|
Number of Colonies:
|
A
|
3
|
B
|
0
|
C
|
2
|
Average:
3+0+2= 5
5/3= 1.67
CFU:
1.67 x 105/0.1= 1.67 x 106
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