Re-using Yeast, is it worth it?

[BrewStew]

I'm thinking of keeping some of the (is it called trub?) yeast sediment from the bottom of my fermentors in a bottle in the fridge.

is it worth it though? i'm a kit brewer so all my kits come with yeast, and i always keep a packet lying around incase i get a stuck brew or duff yeast, and when yeast is less than a quid a sachet i'm wondering if it's worth the hassle?

[steve_flack]

With dry yeast I'd say it isn't worth it as it's cheap and you get plenty in a packet - neither is true of liquid yeasts though.

[fivetide]

I have loads of packets of dried yeast lying around so wouldn't bother, but with DaaB's help I recently saved, stored and grew a large starter out of a pricey liquid yeast I had bought and it was well worth the effort. It really worked a treat and was very satisfying to do. If I had more brews in the offing I would even have split ithe harvested starters for more than one new brew.

[steve_flack]

particularly brewery yeast as it would cost me more than a pack of liquid yeast to drive to the breweries in question.

You should start either making slants or freezing yeast with glycerol. I've got a couple of petri dishes in the brewery right now. One has Crouch Vale's yeast the other has St Bernardus (Belgian - grown from the bottle dregs). Both have viable cultures on them. Tomorrow I'll slant them so I can keep them for posterity.

[steve_flack]

Apparently slants have a shelf life of 4-ish months but there's nothing to stop you reslanting them. The reason for the shelf life is that the agar deteriorates and releases water.

There's a shop on ebay that sells malt extract agar and it's worked pretty well for me so far. It's about £12 a pot but that would make up 2L of agar. I made about 15 slants with 100ml. Oh...and a pressure cooker is very handy.

Acid washing is good if you're re-using yeast from previous fermentations. One problem is that whilst it's pretty good for getting rid of bacteria, it won;t get rid of wild yeasts.

[steve_flack]

This is a great site if you're interesting in getting into yeast work.

http://www.alsand.com/beer/yeast/index_E.html

Honestly the amount of kit required isn't as bad as it seems. Most people around here are pretty resourceful at finding stuff anyway.

[steve_flack]

That's the one.

In the crouch vale sample I got 2nd hand it was very clean (I was expecting worse). Maybe there were some bugs in there but the Petri dish grew up with clean, distinct, identical colonies of yeast. The main thing is not to overload the loop. You'll probably want to dilute the sample you get with sterilised water first and then plate it.

Alternatively you could chance it and go straight to slant and if the yeast sample is clean you'll be OK. You will only need to plate once though and it's probably worth it for a library sample.

[steve_flack]

You'll probably want to dilute the sample you get with sterilised water first and then plate it.

I presume I will need a microscope to determine bacteria from healthy yeast?

Ideally yes but I don't have one and lactic bacteria are officially 'small' so you'll need a good (read expensive) microscope. To date I've used a simple (probably wrong) method to spot yeast. I presume most colonies are yeast (true in brewery samples) if they all look the same then they probably are yeast. If they look odd they're not. Ditch any plate with obvious mould or other wierdness on it.

It's probably a method that generates much head shaking from biologists but I'm a chemist not a biologist.

On another note, will these

Swabs

be suitable for wiping around the neck of glassware before fitting an airlock when making a starter ?

For small bits of glassware I flame the necks with an alcohol lamp (you could use a blowtorch or similar). For starter flasks I'd boil sterilise or use iodophor/peracetic which would be just as good as the swabs.

[bandit]

I want to learn about this so I have added a reply so I can find it in my posts section. Cheers guys, santa needs to bring me a microscope

[Aleman]

I only flame and have no problems.

One thing I'm trying is a 70% IPA (Iso Propyl Alcohol) spray. Maplins do 1L tins of IPA for a sensible amount and as you use it sparingly its fairly cheap. It also makes flaming the necks fun

I'd recommend 'First Steps in Yeast Culturing' which has quite a lot on plating and how to distinguish bacteria from yeast. Basically a good pure yeast culture has a well defined sharp margin, one with infections looks 'fuzzy'. Molds are pretty obvious to spot.

[Aleman]

santa needs to bring me a microscope

Bandit, Santa ought to try Here

Although to be honest, I've been culturing for the last 10 years and still don't have a microscope. The only reason for getting one would be for cell counts and cell viability. even using an Oil Immersion lens at 1600X Yeast cells are obvious, but bacteria are pretty much black dots.

Still for a slide for cell counting try [url=http://www.hawksley.co.uk/cell-count_gl ... ndex.shtml[/url] and the two cell 'bright line' Haemocytometer. You'll need some methylene blue for viability counts. Using a two cell means that you can do a cell count and viability in one go.

[Aleman]

Apparently slants have a shelf life of 4-ish months

Well I've recovered yeast from a brewlab slant after 18 months. with no problems, and if stored on a slant under sterile mineral oil at near freezing then you can store the yeast indefinitely

One of the best ways of storing yeast long term, is to put a cell culture into 2ml of sterile distilled water. This can sit in the fridge until you need it. Take a loopful and inoculate 2ml of wort, when its going build up as usual using the 10X rule (2->20->200->2000ml). If you need to 'prove' the yeast then plate it and select a pure culture from that into the 2ml of wort.

[bandit]

Bandit, Santa ought to try Here

That should come in handy for looking at bees bottoms etc when I do my next bee exam There will be no place for varroa to hide with that beauty. SWMBO is in bed now so I will print a copy and leave it near the dishes

[steve_flack]

That should come in handy for looking at bees bottoms etc

I prefer looking at a different sort of bottom but it takes all sorts I guess.

[gnomey]

Hey Steve, where abouts on ebay can I find the malt extract agar, please?