Nutrient agar?

[bombitmd]

Hey peeps,

I've tried slanting and culturing using the same recipe posted in this forum (agar + dme) and what I've noticed is that my yeast do not grow like the ones I see posted on the forums. I'm supposed to get white or cream colored streaks if the culture is good, right? I only get... what it looked like when I first streaked it. It's like nothing grew. Although, some whitish material settled at the bottom of the tube. The tube smells fine. I've just started to harvest my cultures, so I don't know what it will turn up with as of now.

I'm wondering if it has something to do with the slant I made. (BTW, the yeast I inoculated from gave me great beer, so the yeast source is fine) I'm thinking of using Nutrient Agar which I can get a lab supply store. It consists of:

0.5% Peptone
0.3% beef extract/yeast extract
1.5% agar
0.5% NaCl

Any of you used this? Can I use this for my slant?

 

[WoodlandBrew]

How long and what temperature are you incubating the slants before you lol for growth? Is the liquid from the streak absorbed by the agar, or does it leave a puddle? When you streak are you penetrating the surface of the agar?

To grow the culture on the slant you'll need to add a carbon source to the nutrient agar that you have listed the ingredients.

 

[trentm]

Here is the recipe for the recommended lab media (YPDA) from "Yeast" for 1 liter.

10 grams yeast extract
20 grams peptone
20 grams dextrose (corn sugar)
20 gram agar

I have found this media great for storage but it is not recommended for propagation as it contains no maltose. For propagation use the wort agar you described. Also, for my experience wort agar works find for general lab media including storage. For me, it seems to be less prone to contamination, however, it seems the yeast store a little better on YPDA.

I suspect your issue with growth may have more to do with technique. It takes a little practice to get right. It only takes a little inoculum to do the job. Are you inoculating your slants directly from a starter or fermenting wort using a loop? If so, try using just one loopful and spread it around good on the surface of the slant. As WoodlandBrew suggested you want the media to adsorb the inoculum (no puddles).