Is Fermaid O the same as peptone+dead yeast? Can I substitute them?

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Sep 5, 2017
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Hong Kong
Peptone is one of the major organic nitrogen sources used in microbiology, and it's easy to buy or manufacture yourself by using an enzyme to digest protein (soy protein isolate or casein isolate with no lactose).

It's not so easy to get Fermaid O in my country, and it looks like it just consists of organic nitrogent and exploded dead yeast. Peptone is used for growing mold/yeast/mushrooms, so it seems like this should work, but I haven't tried it yet.

If this is going to work, I need a better way to extract the nutrients from dead yeast. I understand they can be "exploded" osmotically with salt, but that can't be done at home because I wouldn't be able to separate the salt. Is there a well known way to prepare baker's yeast for use as nutrient? If I mix peptone and yeast, which ratio should I use?

Edit: I found a web page that says all that's needed to weaken yeast cell walls is to hold it at 40-50⁰C, and this paper indicates that using a pressure cooker or autoclave followed by fast cooling would be even better. Does this process seem sound? Explode yeast, digest protein with meat tenderizer, filter, dry, mix.

Edit 2: fresh peptone is really hard to filter! I'd say you either need a lab with a centrifuge, or you need a spray dryer so you can make it really thin, filter it, and still get it back to being a reasonable size in the end. Even filtering under vacuum could take hours or days. I'm going to have to order Fermaid O, despite the annoyance of international shipping.
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