If all you're looking to do is maintain a very small yeast bank with minimal effort, you may want to go with pre-poured agar tubes (slants) and plates (Petri dishes). If, however, you intend to do much more than that, the pre-poured option will get VERY expensive, very quickly, and you'll definitely want to make your own. Pre-poured media is available from Cynmar Scientific [link] at the following:
We'll get back to this, with what I consider a much better solution, making your OWN slants and plates.
No matter which way you choose, you will definitely need the following items (or similar), at a minimum....
To begin with, you will need a pressure cooker set at 15 psi (121°C // 250°F). Here's the one I use: 8 qt Pressure Cooker from Pressure Cooker Outlet ($38.49). This is what I refer to as a "Poor Man's Autoclave" or "PMA" (normally I just refer to it as an autoclave, period, with the understanding that a real autoclave is a far more expensive monster—Here is an example of a 2 gallon (8 qt) autoclave from Cynmar. It "only" costs a "mere" $2,125.00 (it's a "value" model)...I'll stick with the pressure cooker!).
Remember, when working with yeast on slants and plates, and up to 10mL starters, this level, all work must be sterile; simply "sanitized" is NOT good enough. At this level, you're working with samples as small as a single cell—even a single cell of beer-spoilage bacteria or wild yeast represents a massive infection.
You will also need the following:
You'll want to filter the wort with one of those cheap, re-usable coffee filters and a funnel (both sanitized, of course—at this point, sanitized is enough, as you are about to autoclave everything to sterilize it).
So, you're getting serious now, and finding the pre-poured media is too expensive, huh? Ok, let's move on to the next stage: making your own culture media. Here's what you'll need in terms of supplies:
You can also buy agar in more expensive forms (some only slightly more expensive) if you prefer.
Note: I do NOT work for Cynmar, even though, as you look at some of this, you might think I do. I have, however, been a very satisfied customer of theirs for about the last decade or so, and have yet to find another vendor to even meet, much less beat, their prices AND quality.
Also be advised that all links to Cynmar pages are subject to a screwy error on their site saying something along the lines of, "Sorry, your session has expired." Just reload the page using your browser's reload/refresh and the page should come up. Sorry...not something I have any control over.