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Napkin Folding — biology

Controlling bacterial growth in fermentation with hurdle technology and survival analysis

Posted by Cameron Davidson-Pilon at

This article is a nice intersection of some of the topics I've been thinking about lately: bacteria, food, and survival analysis, and part of a larger project I've been working on (stay tuned). The bacteria C. Botulinum is responsible for creating one of the most dangerous chemicals known to man: botulinum toxin. If ingested, incredibly small amounts of this toxin can kill even a healthy person. Thankfully, food scientists and microbiologists have developed ways to control C. Botulinum. Any of...

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Bayesian cell counting Pt. 2 - Growth over time

Posted by Cameron Davidson-Pilon at

I’ve started growing yeast in my closet-turned-laboratory. There’s a reason why I am growing yeast, but that’ll be for another post. For this experiment, I wanted to use my new hemocytometer to do cell counts periodically over the next few days to gather data.

A nutrient-rich bioreactor (an Erlenmeyer flask with wort) was left at room temperature with plenty of aeration (a magnetic stirrer) for about 2.5 days. My collected data is below.

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Bayesian cell counting

Posted by Cameron Davidson-Pilon at

Let’s say you are interested in counting the concentration of cells in some sample. This is a pretty common task: sperm counts, blood cell counts, plankton counts. Microbiologists are always counting. Let’s use the example of yeast counting, which is traditional in beer and wine making. The brewery has a sample of yeast slurry, a highly concentrated amount of yeast, and they would like to know how concentrated it is, so they can add the correct amount to a batch....

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