# Biochem Yeast culture problem

1. Nov 14, 2007

### xtracx

Hi,
recently, i've gotten interested in culturing yeast for home-brewing. To keep the costs on the down low, i've made my culture solution (broth) from wholegrain cereal (containing essentil elements & malt extract). Problem is, this 'culture' contains SO2 as a preservative and obviously all micro-0rganisms cannot survive with SO2 around.

Hence, my question is how to removeor neutralise the SO2 in my solution. If possible it should be using home-based solutions to neutralise it. I was thinking of Alkalis, but i'm not too sure on how that will affect the yeast.

Any suggestions?

Thanks

2. Nov 15, 2007

### Staff: Mentor

I've sort of avoided this thread.

Um. Why do you have SO2 in your culture medium? And more important why are you culturing yeast?

If you can show me why you are doing what you seem to be doing maybe I can dredge up some ancient memories to help.

As an aside - professionals have trouble culturing and maintaining a genetically stable yeast culture. Not to mention invader bacteria.

3. Nov 29, 2007

### Ouabache

It sounds like xtracx is interested in culturing yeast to be used for home brewing. That way I read this question, the SO2 was used as a preservative in the whole grain cereal.

4. Nov 29, 2007

### Staff: Mentor

One of my colleques had a degree from UCD in brewing - he indicted that keeping yeast cultures "truw" is very hard indeed. And, normally, the substrate you use for the yeast culture is not the product used for brewing - things need to be carefully controlled, especially in terms of keeping out wild yeasts or bacteria.

And the grain used for brewing always is cleaned first to remove bacteria, preservatives and pesticides. So all of this adds up to 'what is going on' in the first post.... for me. anyway.

5. Nov 30, 2007

### Ouabache

I can believe that. When I cultured isolates of specific fungi, the medium and conditions needed to be carefully controlled to exclude contaminating organisms and maintain phytopathogenicity. If Manraj is still trying to do this empirically, perhaps can find some preservative-free grain to try on the next batch.

6. Dec 1, 2007

### iansmith

Staff Emeritus
When I used to brew, my growth media was only dry malt extract (bought at the bewing centre), some yeast sediment left from a previous batch and tap water. The sediment were mostly yeast and the yeast extract would provide some of the vitamines and amino acid needed. The tap water would provide some minerals and the chlorine would get removed by the sterilisation step.

The yeast grew very well in the medium.

As far as contamination goes, go sterile techniques and sterility of the medium and the euqipement usually prevents alot of problem. Ive only had 2 batches contaminated out of the 100 batches that Ive made.

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