I am using 3 kinds of yeast. I want to add the same amount of the yeast into a dough formulation. I want to add the yeast of about 10^8/ml. I have tried to use OD600, but i still confused how to do this.
There are some method to do this. First, you can convert OD reading to CFU by McFarland conversion (check this reference: http://www.microbiol.org/wp-content/uploads/2011/07/MR13286.pdf). However for yeast, I, myself, do not really recommend this, since the OD is very rough estimate and it can not differentiate between viable and non viable cells.
The second method is by CFU method itself. I assume you have dried yeast. Try to dilute the yeast, and make serial dilutions. Then grow the diluted solution onto agar plates and count the colony number after 2-3 days of incubation. You can get the Colony forming unit by this method. If you grow the cells first, you can use the same protocol.
The third method, is by using haemacytometer. If your target is only the total cell number, you will not need any staining, so you can directly count the cell number under the microscope (check this link: http://futurescienceleaders.org/protocols/files/2013/02/Cell-counting-Neubauer-chamber.pdf). If you need to differentiate viable and non viable cell, you can use methylene blue or methylene violet staining (check this reference: Smart, KA, Chambers, KM, Lambert, I., Jenkins, C., 1999. Use of methylene violet staining procedures to determine yeast cell viability and vitality, J. Am. Soc. Brew. Chem. 57, 18–23). The non viable cell will be stained using this method, so you can count the viable only if that is of your interest.
And the last one is you can use some automatic cell counter instrument to count the cell. It is easy, but you have to find a lab that has it, and due to its small size, not all automatic cell counter can count the yeast. You have to check for their specification.
Hope this help...
Thank you so much. It is really helpful to me. Actually, by using Haemocytometer is really convenient but i have to find out where is that available. The cells viability is also my concern because i will use the yeast as baker's yeast. Anyway i will try all possible methods so i can adjust the number of yeast to be added in the dough.
Glad if it can help.. if you need more detail of the method for differentiating viable and non-viable cell (Smart et al. 1999), I can send the article to you. just send me your e mail address to message, so that I can send the article to your e mail.
Fortunately, today i met my colleague and asking about haemacytometer, and he has it. So this time I will focus on the method of using haemacytometer. Yes please send me the article to [email protected]. Thanks in advance.
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