So I'm starting to collect the stuff to start doing this. I never would have even thought to try so thank you for your videos. I have a couple of questions. They cross a couple of the videos so I think I will try to keep them to the context of each video. In this video you flame the wire tip of the loop, but you don't flame up the handle. Then part of the handle goes inside of the test tube as you are inoculating and rattles around in there. Doesn't that present a chance of contamination in both your slant and in the wort tube?
Thank you Bryan for making these videos and being so generous with your knowledge. They are very clear and well presented. I have found them both instructional and inspiring. They have dispelled the myth that you need lots of space and equipment to start having some fun with yeast. I think I will start by getting some fresh vials of yeast, a loop and burner and grow up some starters using the pop bottle method without stir plates then pitch my split batch beers with different yeasts. I am not sure of the value of stir plates anyway, don't they just suspend the yeast rather than aerate? Thank you again for the fantastic videos.
When I work with different yeast cultures or with bacteria like lactobacillus do I need to sterilise the loop holder? Or is it enough to pass it through the flame…
@@SuiGenerisBrewing ok i understand that i need to sterilize the inoculation loop until glowing red, but my inoculation loop is not long enough and the holder itself is touching the tube, does this matter or is it enough to flame the loop holder(not the loop) a little bit before and after working with a different culture, i hope its understandable whats my question. thanks for your answer.
@@SuiGenerisBrewing ok i clean my workstation when i change the culture, especially after using bacteria. After that i sanitize the handle with isoprop 70% and flame the alcohol of so the handle dont get to hot, i think that should be enough. thanks for your videos i learn a lot from you.
At 2:12 the explanation for why it's often good to pick more colonies is cut out. I found an explanation on your web site, "purifying yeast from infected cultures part 2", where you mention that yeast “strains” are rarely genetically homogeneous and that picking a "single pure colony may not have the same flavour profile as the source strain - and moreover, you also risk picking out a mutant that has a vastly different flavour profile if you use only a single colony". I encourage anyone following this video to read "purifying yeast from infected cultures part 2". The URL of the blog is in the show more section.
I really need to redo this whole series. Between crap audio, bad editing, and poor lighting, I'm surprised anyone watches any of them the whole way through!
Hi Bryan, how do you recommend removing yeast from a slant that has been filled with water? Thanks for all the videos, they have been extremely valuable for me.
I have made a home scale very small Bioreactor for growing up yeast cultures of Kveik Yeast for drying and freezing yeast slurry , Its a 1 quart to 1/2 gallon reactor depending on which jar i use. Basically its a ball airlock lid( the kind for fermenting vegetables with a built in airlock) that i drilled a second hole in and put a stainless steel air stone that is hooked to an air pump and it sits on a Stir plate, so, if my understanding of the process is correct this would be a Very Basic Bioreactor. My issue is the feeding schedule for optimum yeast growth and how much sugar and nutrient i should be feeding it daily. I have Fermax yeast Nutrient and I am doing my Grow up with white Table sugar because its a cheap easy sugar source. I am building up a personal yeast bank of Kveik yeast strains for use in Home wine,beer and mead making. So My goal is the highest biomass I can achieve with the limits of my home made set up. My reactor it self is working so far I am just not sure on a rough estimate of how much sugar and nutrient to feed it daily. I dont have a super accurate Gram scale(yet) so I am using measuring spoons and cups at this point At the present time, I am doing roughly 1/2 teaspoon of yeast nutrient and about 1/4 cup of sugar daily in a 1 quart volume of water I was wondering how these amounts look and if i should change them, if so how much of each would you suggest. The yeast nutrient I have is a General purpose nutrient designed for home wine,beer and mead making. My sugar source is currently white table sugar due to price and ease of access. Any suggestions you can offer would be greatly appreciated.
Hey Bryan, at the end of the video, the step up picture, are you saying that going from a 250 - 300ml starter to a 2L starter will yield roughly 325 billion or do you have to go to 1L to 1.5L then to 2L to get that number? Thanks again for your awesome videos!
Nope, you can go straight to 2L from that volume. As a general "rule" you should see the best yield (in terms of number of new cells/volume wort used) when you are increasing the starter size by about 10-fold.
Sui Generis Brewing, thanks for the quick reply though I’m a little confused. Reading “Yeast, the practical guide to beer fermentation” it states that for a starter volume of 2L, and roughly 100 billion starting cells, it will double 1.1 times yielding 205 billion total cells. If this is true, how can you go from 30-60 billion (from the 250 - 300ml starter) to 325 billion (from a 2L starter) in one jump? Thanks again for the help!
@@MatthewGarrett22 those numbers assume minimal oxygenation and are generally considered to be excessively conservative. For calculations I use Kai Trosters growth curves, which were done using a few strains of yeast in stirred starters.
Hey mate, I have followed you instructions for a long time and have built up a great little bank. I'm trying to cut down on drift and labour, and I want to use a bacteriological loop to harvest the yeast from frozen now. I have just trying stealing 6 samples, I have waited 5 days and no activity from any of them. When pitching my full frozen tubes (50ml total vol) I usually expect a pretty high lag. But once up and going they perform well. I'm thinking I might have to vitality all my frozen starters and it would be better to now store on slants in oil. Would you agree or do you have any ideas? My process with the loop is dip in the frozen mixture and move around, then try and mix it with the wort in the tube. My slurries are all slightly separated for some reason so I'm thinking that potentially the yeast is at the bottom and the separated part just "washes" the yeast off the loop" here is a photo of my frozen yeast to show you what I mean. linksharing.samsungcloud.com/ewyj4ncgNThN
If they've separated the yeast is at the bottom. Separation also reduces yeast viability. When freezing you want to freeze as fast as possible, which helps preserve viability and prevents most separation.
@@SuiGenerisBrewing Thanks for the quick reply. Would it be a stupid idea to get it to a temp where I can pour the top off, take the sample and attempt a refreeze. Or vitality, precool in the fridge and freeze and hope they dont separate this time..?
So i have been following your directions a while. About 35 hours ago I inoculated a tube with california ale yeast that i was storing in mineral oil. I believe with us-05 i would be hearing a major co2 hiss when shaking the yeast and releasing the cap at this point. Are some strains slower to start and if so how long should i wait for clear activity before i assume it failed this time? Maybe i am remembering wrong but it seems slow to me at this point.
@@SuiGenerisBrewing it was an inoculation tube like yours little over half full. Wort was 1.035 gravity before I boiled it a little to boil some off then canned it. I don’t have the exact gravity but should be around 1.040. I took a swipe visible to eye from a slant which I couldn’t grab just one colony. Past photo documentation shows in 18 hours it looked foamier than now but in past I used dme pilsner so I don’t know if me using real wort I made from 2-row would behave different. I think by tomorrow if it doesn’t try to escape like a shaken soda it’s a bust. I may inoculate a new one today and try to save the brew day
@@mattblackburn1450 it can take up to 3 days to see growth, even in a small tube. It takes a bit of time for them to get going, but they'll grow normally once started. Look for the wort going cloudy ans/or sediment as a sign of activity. At small volumes you may not see much bubbling
@@SuiGenerisBrewing thanks. I have had success so far. I think this vial may be missing the seal which would explain no pressure build up. It was canned the day I inoculated this so not worried about infection. Also last time I did California ale I think it was slow compared to us-05 and still came out fine. Yeah I’ll wait and see
Hi Bryan. Thank you for the great videos. I have a package of White Labs Pure Pitch Lager Yeast WLP838. On the back it states that you can use one package with a 3 L starter to make 15 gallons of lager between 1.050 and 1.065. I don’t know if I believe it. Seems a little optimistic to me. What do you think? I’m asking because I trust your judgment more than I trust the marketing team at white labs. I love white labs, don’t get me wrong. I just don’t want to under pitch.
thanks for the videos. Ive read that, vitality is important when propogating yeast, so in order to get 600 or 1000 billion healthy cells from an agar, how would i determine that the yeasts still have that replicating ability...........
If they are actively growing than their viability is considered to be high vitality. So as long as you use the yeast shortly after a starter, it'll be of high vitality. I also have a video in my microscopy series (uBrews) which demonstrates a form of vitality staining to test for vitality.
So just double checking, I want to make sure I get this right... 1. I am supposed to take one of the cultures from the slant tube and place it into a larger tube with DME or regular sugar solution, then wait for 3 to 5 days for the yeast to multiply. 2. After that, I can keep adding this yeast starter to larger and larger vessels of sugars every so often until the yeast multiply to large enough quantities to brew beer correct?
Exactly correct. Make sure you are adding the yeast to a nutrient-rich medium when growing them up for use - e.g. wort. Sugar water doesn't contain enough nutrients for good yeast growth
@@SuiGenerisBrewing Thanks so much! I just have 3 more questions: 1. How do you make a simple wort for doing this? Can I just use DME solution by itself? Or do I need to make the wort like I'm making a beer? (DME mixture with hops and everything else) 2. How much alcohol ABV have you ever gotten on your wild cultivated yeast? 3. Once the yeast starter is completed can it be used to make a wine if yeast nutriant is added? The wine I want to make just consists of water, sugar, acid blend, and grapes. Hope to hear back from you soon!
@@NoahKainWhittington 1) I generally use DME + water to make starter wort, nothing fancy. You can save a few bucks by pressure-canning "extra" wort on brewdays, but that's more work than I'm willing to put into it. Aim for a gravity around 1.040, about 114g DME per litre. 2) Over 15%, although most crap out around 10-12%. 3) Once you have the yeast, decant the liquid and you can then pitch it into whatever you want to make, including for wine. Traditionally, wild wines use the yeast + juice and nothing more. But adding nutrient will give you a finished wine quicker than juice + yeast alone. I'd suggest leaving the acid blend until its time to bottle, as its hard to predict up-front how much you'll need. Instead, pull a small amount of wine the day before you bottle and slowly dose-in the acid blend (weighing it carefully) until the taste is right. Then scale that to the full-sized batch.
@@SuiGenerisBrewing Thank you for the explanation!!! It was very clear! I can't wait to try to cultivate my own yeast. This was a great serries you've done. It has helped me understand wild yeast so much better!!! Thank you so much dude!
Sui Generis Brewing hi! Thanks for the great videos! Is the nutrients the reason why we have to scale the wort mixes up slowly from test tube to a cup to a liter to several litres? Thanks again for spreading all your great advise!
You should flame sterilize your inoculating loop at a length (plus a little more) at least as deep as your inserting into the tube/slant. Your increasing your risk of contamination by not doing that.
@@SuiGenerisBrewing thanks so much sir... sir I have another question hope you can answer it... when you autoclaving your DME it looks clear and all the trub separate in bottom..how its happen? I try with my own way with boiling never got clear like when autoclaving or steaming...maybe you can record a content about how to make clear worth without chemical...thanks
If I wanted how to capture wild yeast, 1) how do I know what to look for if I ever get it on a plate, selecting yeast instead of something else 2) how do I know if it’s safe
I've addressed these questions on my blog, in a series of articles on hunting wild yeasts: suigenerisbrewing.com/index.php/tag/hunting-wild-yeasts/ More shortly, its rather easy. The "trick" is to let the wild culture ferment for at least 3 or 4 months, in a container properly sealed with an airlock. Over that time, the increasing alcohol and acidity will kill off anything dangerous and select for beer-friendly yeasts & bacteria. As such, anything you isolate after this timepoint should be safe - as in non-pathogenic/non-toxic yeasts and lactobacilli. This months-old ferment can then be plated to isolate pure cultures (see my streak plate video on how to do this, th-cam.com/video/mCOtWztCObY/w-d-xo.html). The resulting plate will contain a mixture of yeast and lactobacilli colonies. If you don't want the later, make your agar plates with wort containing >25 IBU of hops (using wort from an IPA brewday is a great way to do this). That should suppress the lacto, allowing only yeast to grow on your plate.
I've learned so much from watching your videos. Great resource and thank you so much!!
Thanks!
Great video, Bryan! Thanks for the great content! Got myself a new Bunsen burner for Christmas, and can’t wait to get back to my yeast lab!
Dude . You rock ! Well explain , details , example . Everything here !
So I'm starting to collect the stuff to start doing this. I never would have even thought to try so thank you for your videos.
I have a couple of questions. They cross a couple of the videos so I think I will try to keep them to the context of each video.
In this video you flame the wire tip of the loop, but you don't flame up the handle. Then part of the handle goes inside of the test tube as you are inoculating and rattles around in there. Doesn't that present a chance of contamination in both your slant and in the wort tube?
It is a risk, and ideally I'd have a longer wire. I do sanitize the handle with isopropyl before I start working which helps reduce the risk.
Your videos are excellent. Thank you for providing such useful homebrew | home-lab information.
Thank you Bryan for making these videos and being so generous with your knowledge. They are very clear and well presented. I have found them both instructional and inspiring. They have dispelled the myth that you need lots of space and equipment to start having some fun with yeast. I think I will start by getting some fresh vials of yeast, a loop and burner and grow up some starters using the pop bottle method without stir plates then pitch my split batch beers with different yeasts. I am not sure of the value of stir plates anyway, don't they just suspend the yeast rather than aerate? Thank you again for the fantastic videos.
Stir plates are worth every penny. You'll getvmuch faster growth and higher yeast yields (2-10x, depending on strain)
When I work with different yeast cultures or with bacteria like lactobacillus do I need to sterilise the loop holder? Or is it enough to pass it through the flame…
You want to hold it in the flame until it grows a dull red. More than that is excessive, bit under-flaming can lead to contamination.
@@SuiGenerisBrewing ok i understand that i need to sterilize the inoculation loop until glowing red, but my inoculation loop is not long enough and the holder itself is touching the tube, does this matter or is it enough to flame the loop holder(not the loop) a little bit before and after working with a different culture, i hope its understandable whats my question. thanks for your answer.
@@TodayTestfbsfbsfbs it's not a bad idea to sanitize the handle, but I wouldn't flame it as it may get too hot to use.
@@SuiGenerisBrewing ok i clean my workstation when i change the culture, especially after using bacteria. After that i sanitize the handle with isoprop 70% and flame the alcohol of so the handle dont get to hot, i think that should be enough. thanks for your videos i learn a lot from you.
At 2:12 the explanation for why it's often good to pick more colonies is cut out. I found an explanation on your web site, "purifying yeast from infected cultures part 2", where you mention that yeast “strains” are rarely genetically homogeneous and that picking a "single pure colony may not have the same flavour profile as the source strain - and moreover, you also risk picking out a mutant that has a vastly different flavour profile if you use only a single colony". I encourage anyone following this video to read "purifying yeast from infected cultures part 2". The URL of the blog is in the show more section.
I really need to redo this whole series. Between crap audio, bad editing, and poor lighting, I'm surprised anyone watches any of them the whole way through!
I wouldn’t change anything, this series is perfect. Don’t ever take it down! Learnt so much.
Hi Bryan, how do you recommend removing yeast from a slant that has been filled with water? Thanks for all the videos, they have been extremely valuable for me.
Gently scrape it off with a loupe and transfer to a small (5-10 ml) starter
I have made a home scale very small Bioreactor for growing up yeast cultures of Kveik Yeast for drying and freezing yeast slurry , Its a 1 quart to 1/2 gallon reactor depending on which jar i use.
Basically its a ball airlock lid( the kind for fermenting vegetables with a built in airlock) that i drilled a second hole in and put a stainless steel air stone that is hooked to an air pump and it sits on a Stir plate, so, if my understanding of the process is correct this would be a Very Basic Bioreactor.
My issue is the feeding schedule for optimum yeast growth and how much sugar and nutrient i should be feeding it daily. I have Fermax yeast Nutrient and I am doing my Grow up with white Table sugar because its a cheap easy sugar source.
I am building up a personal yeast bank of Kveik yeast strains for use in Home wine,beer and mead making. So My goal is the highest biomass I can achieve with the limits of my home made set up.
My reactor it self is working so far I am just not sure on a rough estimate of how much sugar and nutrient to feed it daily. I dont have a super accurate Gram scale(yet) so I am using measuring spoons and cups at this point
At the present time, I am doing roughly 1/2 teaspoon of yeast nutrient and about 1/4 cup of sugar daily in a 1 quart volume of water I was wondering how these amounts look and if i should change them, if so how much of each would you suggest. The yeast nutrient I have is a General purpose nutrient designed for home wine,beer and mead making. My sugar source is currently white table sugar due to price and ease of access. Any suggestions you can offer would be greatly appreciated.
Hey Bryan, at the end of the video, the step up picture, are you saying that going from a 250 - 300ml starter to a 2L starter will yield roughly 325 billion or do you have to go to 1L to 1.5L then to 2L to get that number? Thanks again for your awesome videos!
Nope, you can go straight to 2L from that volume. As a general "rule" you should see the best yield (in terms of number of new cells/volume wort used) when you are increasing the starter size by about 10-fold.
Sui Generis Brewing, thanks for the quick reply though I’m a little confused. Reading “Yeast, the practical guide to beer fermentation” it states that for a starter volume of 2L, and roughly 100 billion starting cells, it will double 1.1 times yielding 205 billion total cells. If this is true, how can you go from 30-60 billion (from the 250 - 300ml starter) to 325 billion (from a 2L starter) in one jump? Thanks again for the help!
@@MatthewGarrett22 those numbers assume minimal oxygenation and are generally considered to be excessively conservative. For calculations I use Kai Trosters growth curves, which were done using a few strains of yeast in stirred starters.
Sui Generis Brewing , awesome, thank you again for the clarification and sweet info! I’ve started my own slant bank mimicking your videos.
Very good video. Thank you very much for sharing your knowledge! =)
Hey mate,
I have followed you instructions for a long time and have built up a great little bank.
I'm trying to cut down on drift and labour, and I want to use a bacteriological loop to harvest the yeast from frozen now.
I have just trying stealing 6 samples, I have waited 5 days and no activity from any of them.
When pitching my full frozen tubes (50ml total vol) I usually expect a pretty high lag. But once up and going they perform well.
I'm thinking I might have to vitality all my frozen starters and it would be better to now store on slants in oil.
Would you agree or do you have any ideas?
My process with the loop is dip in the frozen mixture and move around, then try and mix it with the wort in the tube.
My slurries are all slightly separated for some reason so I'm thinking that potentially the yeast is at the bottom and the separated part just "washes" the yeast off the loop" here is a photo of my frozen yeast to show you what I mean. linksharing.samsungcloud.com/ewyj4ncgNThN
If they've separated the yeast is at the bottom. Separation also reduces yeast viability. When freezing you want to freeze as fast as possible, which helps preserve viability and prevents most separation.
@@SuiGenerisBrewing Thanks for the quick reply.
Would it be a stupid idea to get it to a temp where I can pour the top off, take the sample and attempt a refreeze.
Or vitality, precool in the fridge and freeze and hope they dont separate this time..?
@@jessoman refreshing will kill most of the yeast. Best bet is to make a new frozen stock from a fresh starter.
@@SuiGenerisBrewing would it be okay to run a single vitality of the frozen stuff and freeze that 😊
@@jessoman yep
So i have been following your directions a while. About 35 hours ago I inoculated a tube with california ale yeast that i was storing in mineral oil. I believe with us-05 i would be hearing a major co2 hiss when shaking the yeast and releasing the cap at this point. Are some strains slower to start and if so how long should i wait for clear activity before i assume it failed this time? Maybe i am remembering wrong but it seems slow to me at this point.
How much wort (volume), at at what gravity, did you use. And did you transfer 1 colony or several?
@@SuiGenerisBrewing it was an inoculation tube like yours little over half full. Wort was 1.035 gravity before I boiled it a little to boil some off then canned it. I don’t have the exact gravity but should be around 1.040. I took a swipe visible to eye from a slant which I couldn’t grab just one colony. Past photo documentation shows in 18 hours it looked foamier than now but in past I used dme pilsner so I don’t know if me using real wort I made from 2-row would behave different. I think by tomorrow if it doesn’t try to escape like a shaken soda it’s a bust. I may inoculate a new one today and try to save the brew day
@@mattblackburn1450 it can take up to 3 days to see growth, even in a small tube. It takes a bit of time for them to get going, but they'll grow normally once started. Look for the wort going cloudy ans/or sediment as a sign of activity. At small volumes you may not see much bubbling
@@SuiGenerisBrewing thanks. I have had success so far. I think this vial may be missing the seal which would explain no pressure build up. It was canned the day I inoculated this so not worried about infection. Also last time I did California ale I think it was slow compared to us-05 and still came out fine. Yeah I’ll wait and see
@@SuiGenerisBrewing also anytime someone talks about yeast practices and interest in doing this i always refer your channel as the best resource.
Hi Bryan. Thank you for the great videos. I have a package of White Labs Pure Pitch Lager Yeast WLP838. On the back it states that you can use one package with a 3 L starter to make 15 gallons of lager between 1.050 and 1.065. I don’t know if I believe it. Seems a little optimistic to me. What do you think? I’m asking because I trust your judgment more than I trust the marketing team at white labs. I love white labs, don’t get me wrong. I just don’t want to under pitch.
It may be reasonable. 3L is a pretty big starter, and depending on the starting cell count, would get you in the ballpark of an appropriate pitch rate
thanks for the videos. Ive read that, vitality is important when propogating yeast, so in order to get 600 or 1000 billion healthy cells from an agar, how would i determine that the yeasts still have that replicating ability...........
If they are actively growing than their viability is considered to be high vitality. So as long as you use the yeast shortly after a starter, it'll be of high vitality. I also have a video in my microscopy series (uBrews) which demonstrates a form of vitality staining to test for vitality.
Your channel is awesome =)
Thanks!
Useful? Awesome!
So just double checking, I want to make sure I get this right...
1. I am supposed to take one of the cultures from the slant tube and place it into a larger tube with DME or regular sugar solution, then wait for 3 to 5 days for the yeast to multiply.
2. After that, I can keep adding this yeast starter to larger and larger vessels of sugars every so often until the yeast multiply to large enough quantities to brew beer correct?
Exactly correct. Make sure you are adding the yeast to a nutrient-rich medium when growing them up for use - e.g. wort. Sugar water doesn't contain enough nutrients for good yeast growth
@@SuiGenerisBrewing Thanks so much! I just have 3 more questions:
1. How do you make a simple wort for doing this? Can I just use DME solution by itself? Or do I need to make the wort like I'm making a beer? (DME mixture with hops and everything else)
2. How much alcohol ABV have you ever gotten on your wild cultivated yeast?
3. Once the yeast starter is completed can it be used to make a wine if yeast nutriant is added?
The wine I want to make just consists of water, sugar, acid blend, and grapes.
Hope to hear back from you soon!
@@NoahKainWhittington
1) I generally use DME + water to make starter wort, nothing fancy. You can save a few bucks by pressure-canning "extra" wort on brewdays, but that's more work than I'm willing to put into it. Aim for a gravity around 1.040, about 114g DME per litre.
2) Over 15%, although most crap out around 10-12%.
3) Once you have the yeast, decant the liquid and you can then pitch it into whatever you want to make, including for wine. Traditionally, wild wines use the yeast + juice and nothing more. But adding nutrient will give you a finished wine quicker than juice + yeast alone. I'd suggest leaving the acid blend until its time to bottle, as its hard to predict up-front how much you'll need. Instead, pull a small amount of wine the day before you bottle and slowly dose-in the acid blend (weighing it carefully) until the taste is right. Then scale that to the full-sized batch.
@@SuiGenerisBrewing Thank you for the explanation!!! It was very clear! I can't wait to try to cultivate my own yeast. This was a great serries you've done. It has helped me understand wild yeast so much better!!!
Thank you so much dude!
Sui Generis Brewing hi!
Thanks for the great videos!
Is the nutrients the reason why we have to scale the wort mixes up slowly from test tube to a cup to a liter to several litres?
Thanks again for spreading all your great advise!
You should flame sterilize your inoculating loop at a length (plus a little more) at least as deep as your inserting into the tube/slant.
Your increasing your risk of contamination by not doing that.
You should...unless you have a handle like mine which has plastic bits inside that'll melt if you do that.
@@SuiGenerisBrewing I figured you knew this...it was just meant for people that may not, and then leading them to future failures.
if we are culturing yeast...how to detect any contamination in our culture? any test or sign ...please tell me ..thanks
Make a streak plate, and look for any unusual or different colonies.
@@SuiGenerisBrewing thanks
@@SuiGenerisBrewing hello sir ...if I want culture yeast from step 1 go straight to step 3 can or not sir ? give me a reason thanks.
@@WildWisdomA stirring increases yield,but is not strictly required
@@SuiGenerisBrewing thanks so much sir...
sir I have another question hope you can answer it...
when you autoclaving your DME it looks clear and all the trub separate in bottom..how its happen?
I try with my own way with boiling never got clear like when autoclaving or steaming...maybe you can record a content about how to make clear worth without chemical...thanks
If I wanted how to capture wild yeast, 1) how do I know what to look for if I ever get it on a plate, selecting yeast instead of something else
2) how do I know if it’s safe
I've addressed these questions on my blog, in a series of articles on hunting wild yeasts: suigenerisbrewing.com/index.php/tag/hunting-wild-yeasts/
More shortly, its rather easy. The "trick" is to let the wild culture ferment for at least 3 or 4 months, in a container properly sealed with an airlock. Over that time, the increasing alcohol and acidity will kill off anything dangerous and select for beer-friendly yeasts & bacteria. As such, anything you isolate after this timepoint should be safe - as in non-pathogenic/non-toxic yeasts and lactobacilli.
This months-old ferment can then be plated to isolate pure cultures (see my streak plate video on how to do this, th-cam.com/video/mCOtWztCObY/w-d-xo.html). The resulting plate will contain a mixture of yeast and lactobacilli colonies. If you don't want the later, make your agar plates with wort containing >25 IBU of hops (using wort from an IPA brewday is a great way to do this). That should suppress the lacto, allowing only yeast to grow on your plate.
Moist Critical penguinz0