Restreaking from older yeast slants

[Simonh82]

I have a small collection of yeast cultures that I keep on slants. Some of them are getting on for 6 months old and I'd like to restreak them onto fresh slants to keep the strain going. Is it fine to just transfer and streak directly from the old slant onto a new one? Will the viability of the yeast have deteriorated significantly during storage and will it grow new healthy cultures on the fresh slant, or will they have suffered from the long storage? As I'm planning on using the old slant for a brew, would it be better to grow that up in a small starter and take a slant from that, increasing the vitality of the cells being streaked? The obvious issue being that this would increase the risk of introducing contamination, even if it were at a very low level you might find in a starter that had been boiled for 15 minutes.

Any thoughts on the best way to proceed would be appreciated.

 

[cswis86]

I would remove some yeast from your slant and inoculate them into about 10-50ml of sterile wort, let that grow for a 48 hours then take a loop full of yeast and streak some new slants. As long as you keep everything sanitary I wouldn't worry about contamination. It's more important to make sure you have healthy viable yeast. Are the slants being stored in the fridge? 6 months is a pretty long time to store them at fridge temps. You might want to look into getting some glycerol so you can freeze them.

 

[ba-brewer]

I have a small collection of yeast cultures that I keep on slants. Some of them are getting on for 6 months old and I'd like to restreak them onto fresh slants to keep the strain going. Is it fine to just transfer and streak directly from the old slant onto a new one? Will the viability of the yeast have deteriorated significantly during storage and will it grow new healthy cultures on the fresh slant, or will they have suffered from the long storage? As I'm planning on using the old slant for a brew, would it be better to grow that up in a small starter and take a slant from that, increasing the vitality of the cells being streaked? The obvious issue being that this would increase the risk of introducing contamination, even if it were at a very low level you might find in a starter that had been boiled for 15 minutes.

Any thoughts on the best way to proceed would be appreciated.

I am in the same boat, but some of my slants are getting close to 10months. I see some places that say to just re-streak from the slant and other places say to regenerate. I have made slants from dipping into the packet of yeast and some from dipping into the starter because the packet was sort of old and the ones made from dipping into the starters always filling in faster. I am leaning toward making small starters to re-slant.

If you are slanting then you should have a pressure cooker or autoclave so you can sterilize your starter media to minimize the chance of contamination. I use 4oz and 8oz mason jars to make sterilize small amounts of worts for the first few step when building from a slant.

If you look through the slanting sticky some people streak a plate with yeast from the slants and build from a few selected colonies. That seems like the way to go if you want to get relatively pure sample.

I believe you can let slants go up to a year as long they stay refrigerated, but it also says it is strain dependent. I think as long as the yeast is still creamy and not turned dark you are OK. Recently used a 10month old slant to brew a beer and it came to life just fine.