Your Home Yeast Lab Made Easy – Streak Plates
The fourth of my “Your Home Yeast Lab Made Easy” series is now up on youtube. This video covers an advanced topic – streak plating. I was not planing on covering this topic so early in my video series, but I was streaking yeast for another project and decided to take advantage of the situation.
Streak plating is used any time you need to purify a strain of yeast (or other microorganism). This method allows you to pull single, genetically pure strains of a microorganism out of a mixed culture. This mixed culture could be any number of sources – an old strain of yeast whose characteristics are starting to drift, a contaminated batch of yeast, a mixed culture (e.g. those made by Wyeast, or from a bottle of sour beer), or even from a wild ferment you started using yeast from your back yard!
The principal of streak plating is simple – a small amount of the source yeast is spread across an edge of a petri dish. The yeast/bacteria/etc concentration in this streak are at a high density, so you swipe a sterilized loop across the first set of streaks, picking up a small number of the organisms, and then streak over another portion of the plate. You repeat this two more times, each time diluting out the yeast/etc further.
4 thoughts on “Your Home Yeast Lab Made Easy – Streak Plates”
I'm just getting the hang of streaking my own plates to isolate wild yeasts for the first time. I'm also excited about being able to bank some commercial strains. While I was streaking today (clothes on this time), I thought, "How would you go about banking a blend?" Can you go straight to a slant, and just take a wider swath with your loop? Is it a better bet to isolate all three (for example), then grow them up in three 7mL tubes, then pitch them all into a 250mL starter? Ideas?
These videos are superb, I wish this video serie is going to keep growing as I'm really interested in these DIY and low-cost techniques. As a student in Humanities and without a science-related degree, every places I contacted denied me access to their laboratory and equipments and sadly make a large part of natural science elitist. Also, is it possible at all to yeast hunt without any sort of microscope? Thank you!
What kind of sterilized loops would you recommend to buy?
I’d suggest something like this: https://a.co/d/4KdkuXw
Essentially, its a reusable handle with nicrome-wire loops. Generally speaking, you want a loop around 5 mm in diameter. Use a loop until it breaks, then swap it out for a new one. With care, one loop shoudl be good for a few hundred transfers.