The microbrewery would like to produce a 50gallon trial batc

The microbrewery would like to produce a 50-gallon trial batch of Ale which requires a pitch rate of 12 million cells/ml or wort. The yeast is first grown in a defined growth medium and the cells are harvested by centrifugation. a. How many yeast cells are required to achieve the correct cell density in 50 gallons of Ale wort? b. Yeast can grow to about 2 times 10^8 cells/ml. To be able to harvest this many yeast cells, what volume of yeast culture do you need to grow to correctly pitch a wort the volume of 50 gallons? Show you work The arrow points to an isolated colony on this plate. What is the minimum number of yeast cells that were needed to produce this colony? You have two cultures of the same strain of yeast in the same medium. You determine that the OD_600 the two cultures is about the same, but when you determine the number of cells per ml for both cultures, the numbers differ significantly. The table below shows a summary of your data. Briefly explain the reason for this discrepancy.

Solution

How many yeast cells are required to achieve the correct cell density in50 gallons of Ale Wort?

You mentioned that you require a pitch rate of 12 million cells/ml of wort

Now you want to know how many yeast cells are required to achieve the correct cell density in 50 gallons of Ale wort=

1 gallon=3785 milliliters or ml

50 gallons=50 * 3785 milliliters=189250 milliliters or ml

1 million=10,00,000

12 million cells/ml=12,000,000 cells/ml

=(12,000,000 cells/ml) x (189250 milliliters)= 2.271x10¹² cells

Number of yeast cells required to achieve the correct cell density in 50 gallons of Ale Wort=2.271x10¹² cells

Yeast can grow to about 2x108 cells/ml. To be able to harvest this many yeast cells, what volume of yeast culture do you need to grow to correctly pitch a wort the volume of 50 gallons?

Cell can grow about=2x10⁸ cells/ml.

You need a cell density of 2.271x10¹² cells for 50 gallons of Ale wort.

If 2x10⁸ cells are present in 1 ml

Then 2.271x10¹² cells are present in how many ml = (2.271x10¹² cells) x (1 ml)/(2x10⁸ cells)=11355 ml or 11.355 liters

What is the minimum number of yeast cells that were needed to produce this colony?

Just one cell is enough to produce one colony. Carefully pick one cell and inoculate on Petri plate containing suitable medium. After incubation you can see individual colonies growing form each cell.

Why there will discrepancy between the cells predicted by OD values and spot plating?

If you consider OD, this take actively dividing, viable cells, cells in stationary phase and dead cells into consideration while giving you the predicted number of cells/ml, but in case of spot plating, only actively dividing cells are taken into consideration. This is the reason why OD values always will not provide an accurate details about how many cells are there in the culture tubes. Some times by absorbing more light larger cells will introduce aberrations in your OD readings, but this will not happen with spot plating.