The idea of wild yeast capture, sometimes known by the much cooler name bioprospecting, for making beer has interested me for a long time. I have started down this path a couple of times, with my first attempt successfully capturing a yeast from a blend of Michigan grown apples pressed into cider. This was used in my first attempt at making a sour beer. While I’ve still yet to really evaluate the profile of that yeast past “it ferments and doesn’t taste bad”, I know it to be a voracious fermenter easily consuming even some longer chain polysaccharides found in maltodextrin after being dormant for the better part of a year. My second attempt came last year when I harvested some mulberries from a nearby tree. This started fermenting, but I apparently over oxygenated and it grew mold so I tossed it.

I’m going to increase my efforts this year to capture local yeast and I’ve even volunteered to lead an educational session for the AABG in May specifically focusing on how to capture, grow, and use wild yeast. When the weather gets better, I’m going to try some open air capture in my back garden while the plants are coming back to life and flowers are starting to bloom. Then when the fruit starts to come in, I’ll harvest from that as well and see if the result differ over the course of the year. I hope to have enough captured and grown up to ferment a beer or two in time for the May educational session.

2017 Bioprospecting Plan

Step 1: Attempt a spring time open air capture using jars of wort and nylon or cheesecloth to keep large particulars and bugs out. I’ll do this with hopped and unhopped wort to see if either works better, or maybe I can get a good sour bug separate in addition to an isolated yeast strain.

Step 2: Harvest fruit directly into wort and see what grows. To see if the local microbes change throughout the season, I’ll try harvests at different times and in different ways. When my berry bushes start to ripen, I’ll create starter jars for each kind of berry and see what I get. I expect I’ll get the same yeast from all the berries given the proximity of the plants, but it’s possible that different conditions on different fruits (pH, sugar content, etc) might alter the microbial balance to a degree.

Step 3: Fall open air capture the same way as the spring capture. We have a green space behind out house that blooms in the fall with goldenrod which bloom late here and could provide a resurgence of pollen in the air carrying potentially new things to ferment with.

Post-Bioprospecting Fermentation

Once I have the yeast(s) captured I’ll brew up a beer that is mostly neutral so I can really evaluate the yeast profiles understand my standard fermentation profile, which is start at 68F for 24-36 hours and then step up to 70F to finish out. I’ll probably go with my West Country White Ale, minus the honey, and then split ferment.

After I have the beers evaluated and the best yeast(s) picked, I will probably plate the cultures out and isolate the colonies. Then I’ll repeat the split ferment using a different beer, which will depend on the yeast profiles. Ultimately I may even setup slants to keep the cultures happy and healthy long term if I like them enough. I’ll be sure to update with more on this project as it moves along.

DIY Bioprospecting

Want to try this yourself? Great, you should! Here are some resources to help you out: