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Baking Vitabread
Part of our Vitayeast project was to see if we could use our yeast in the applications we envisioned. We decided to bake bread out of the Vitamin A strain of yeast.
Finding the OD of Dry Active Yeast (Store-bought Yeast)
- Mix 1 packet dry active yeast in 250 ml of freshly made YPD, heated up to 45°C.
- Wait 10 minutes, while swirling the mixture occasionally.
- Measure OD of 1/100 dilution.
- Calculate total OD of 1 packet.
Using the spectrometer, we calculated the following ODs:
A600(1/100)
- 0.171 A
- 0.080 A
- 0.290 A
Average: 0.180
0.180x100 = 18 OD/ml
18 OD/ml * 350 ml = 6312 OD/loaf
The values for this OD were inconsistent, so a second batch of OD was taken.
A600(1/50)\\ 0.328 A\\ 0.360 A\\ 0.377 A\\
Average: 0.355
0.355x50 = 17.75 OD/ml
17.75 OD/ml*350 ml = 6213 OD/loaf
This is about 650 colonies.
Measuring the OD of a Lawn of Vitamin A Yeast
A600(1/200)\\ 0.206 A\\ 0.230 A\\ 0.206 A\\
Use the value 0.206.
0.206 OD/ml*200 = 40 OD/ml x 17 ml = 680 OD
If we want a 1:1 ratio of Vitamin A yeast to dry yeast, then we would need 9.1 plates. This weighs 0.68 g. Sources on the internet say that the ratio of fresh yeast to dry yeast in bread baking should be 1:2. If this is true, then you need 14 grams, which is 26 small plates.
Growing Vitamin A Yeast for Bread
We decided to grow up the yeast cells in culture in multiple 500 ml Erlenmeyer flasks and also grow the wild type of that yeast strain for benchmarking purposes. There are three flasks of the Vitamin A yeast and WT each, with 250 ml of YPD media in each, and OD measurements were taken to see how concentrated the cultures were.
After one day, we took the OD.
0.435 OD/ml * 20 = 8.7 OD/ml * 750 ml = 6525 for all three flasks. This means that the total weight would be around 6.5 g.
We decided to let the yeast incubate further in culture.
After another day, we took the OD again.
A600(1/50) \\ 0.386 A\\ 0.388 A\\ 0.426 A\\
Average: 0.400 OD/ml.
0.400 OD/ml * 50 = 20 OD/ml * 750 ml = 15000 for all three flasks. This means that the total weight is around 15 g.
The cells were then placed in a cold room. Two days later, the OD was remeasured, this time for both the WT yeast and the Vitamin A yeast.
WT yeast: A600(1/50)\\ 0.334 A\\ 0.291 A\\ 0.396 A\\
Average for WT yeast: 0.3403 OD/ml 0.3403 OD/ml * 50 = 17 OD/ml * 750 ml = 12762.5 for all three flasks of WT yeast.
Vitamin A yeast: A600 (1/50)\\ 0.427 A\\ 0.426 A\\ 0.383 A\\
Average for Vitamin A yeast: 0.412 OD/ml 0.412 OD/ml * 50 = 20.6 OD/ml = 15450 for all three flasks of Vitamin A yeast
On 9/19/2011, we decided to test out the Vitamin A yeast for baking.
The 20.6 OD/ml translated to about 0.02 g/ml of yeast. We need 14 grams of lab yeast to bake, so this means that we would need 700 ml of the lab yeast to do so.
