Lactose busillius won't grow on slant.

[krops13]

I can't get the lactose busillius to grow on my slant. I've grown yeast on one so I know there viable. Is there a special way of doing it?

 

[TheWhaleShark]

I can't get the lactose busillius to grow on my slant. I've grown yeast on one so I know there viable. Is there a special way of doing it?

I take it you mean Lactobacillus, the genus of lactose-fermenting bacteria? What kind of slant are you using?

EDIT: Also, are you incubating the slant or leaving it at room temperature? Bacteria work differently than yeast.

 

[krops13]

Yea that's what I ment I was trying to post and work at the same time. I am leaving them at room temp the media is a malt extract agar.

 

[Bsquared]

Yea that's what I ment I was trying to post and work at the same time. I am leaving them at room temp the media is a malt extract agar.

Thats your problem, they will do best at 37ºC (98.6ºF). They are probably growing just really slow. You might want to try and rig up and incubator. or put them on a heating pad set to low. They work really well in a 120ºF sour mash so if you are between 99-120ºF you should be good in 24hr.

 

[TheWhaleShark]

Yea that's what I ment I was trying to post and work at the same time. I am leaving them at room temp the media is a malt extract agar.

Ah, OK.

There are a few things you need to know. First, you need to incubate them, or else it won't grow properly. Bacteria do not propagate very readily at room temperature, and Lactobacillus especially so. They're part of the normal flora of the vagina and the intestinal tract, so they need warm conditions to support growth.

Second, Lactobacilli need a source of lactose and other special nutrients. A typical malt extract agar does not contain these. You can add a bit of pure lactose to the slant the next time you make it, or you can try using nonfat dry milk. That will add both lactose and several essential proteins. You also need to add yeast extract in some fashion. I think a small amount of vegemite or marmite may suffice in that regard.

Third, Lactobacilli grow best under slightly acidic conditions. Malt extract agar is usually way too acidic to allow bacterial growth. You need to adjust the pH of your media up to around 6.8 to 7.0. Malt extract agar is typically below pH 5.

Here is a link to a formulation for a Lactobacillus agar. You'll note an interesting component: dehydrated tomato juice. It appears that the tomato juice sufficiently acidifies the media and provides other essential nutrients to the bacteria. I would get some tomato juice, boil it down to a paste, and dry it out in the oven.

Finally, they're facultative organisms, meaning that they grow both aerobically and anaerobically. They seem to do better anaerobically, so it might be better to do a stab culture rather than a slant. Just put the molten agar into a tube, sterilize it, and let it solidify on a level surface. Then you just inoculate a portion of the bacteria vertically by stabbing into the media.

So, in summary, it's a lot of work. You might want to think of another way to get it in there. Have you considered putting a teaspoon of plain nonfat yogurt into your mash? I doubt you'll detect the taste, but that should provide a sufficient innoculum.

 

[TXCrash]

Correct me if I'm wrong - but don't grains already have a bunch of lacto on them?

Isn't it a common practice in sour mashing to toss a handful of malt into a mash to inoculate the mash?

Or did I interpret something wrong?

 

[ChrisKennedy]

Correct me if I'm wrong - but don't grains already have a bunch of lacto on them?

Isn't it a common practice in sour mashing to toss a handful of malt into a mash to inoculate the mash?

Or did I interpret something wrong?

Sour mashing produces a different result than a pure lactobacillus fermentation.