How To: Culture Lactobacillus (LAB) for Horticultural use

Generally when it comes to bacteria and microbes we'd be referring to the aerobic type you'd hope to produce in a Compost Tea (AACT) system, the reason being that the presence of anaerobic bacteria in these systems are nearly always 'bad news'. However there are useful anaerobes out there and it is very much worth looking in to putting them to use in your horticultural endeavours!!

Enter Lactobacillus....

Lactobacillus is a facultive anaerobe that we are generally interested in for it's ability to ferment a wide variety of things. It is this process that makes Lactobacillus or LAB the cornerstone of a range of processes the savvy gardener will find extremely useful. I'll mention more about that later in this piece and in further blogs, but lets show you how to culture your own Lactobacillus first....

Step 1 - Rice wash

Technically you can use any reasonable carbohydrate source (preferably not simple sugars) but in this instance we'll go with a Rice wash - I will be trying other more exciting things in the future, but until then..... Well the title says it all really, wash some rice and collect the water. This milky wash will now contain some of the starches from the rice and provide a food source for your bacteria.

Step 2 - Collect your initial culture

Place your rice wash in a suitable vessel (a jar...) and protect the neck with some kind of net to stop anything random getting in. Ideally you'll want to place this outside, in a garden, on a balcony ect away from the elements but open to the air. This will allow the bacteria to go to work on the wash. A day or so should be fine. You will notice a change in the wash as the bacteria start to work, it will start to smell slightly sour and three distinct layers should be visible. You now need to collect the middle of these layers - the best way is with a siphon, but a syringe or whatever you have to hand will work - just try not to disrupt the layers.

Step 3 - Feed the LAB

Now it's time to culture just the LAB that are present and nothing else. To do this we add milk to the liquid we collected at about 10:1, so for every 10ml of liquid you want to add 100ml of milk - You can use pretty much any milk as it's the LAB in the wash we are culturing, however the least adulterated milk you can get your hands on the better. It's probably worth saying you can't use a lactose free milk for fairly obvious reasons....Finally we want to store this in an anaerobic state, so you have a few options - Ideally you can use a container with an airlock - the same as homebrewers use (or make one), you could use a bottle or jar and release the pressure every so often (not the best plan) or as I have use a heavy lid with a seal so any gas can escape but will then re-seal (not ideal to be honest....go buy some airlocks, you'll want them for further projects!)

Step 4 - Prep & Store the LAB

After about a week you should notice a distinct change - You'll have a layer of curds and a liquid layer - whey. It's this liquid layer we want. Nothing too stressful here, just use a sieve and collect the liquid in a vessel - The curds can be put on the compost or whatever, it will be a great addition. Again your brew should smell sour (actually quite pleasant if you're in to sour beers at all....) but not rancid, if it is bin it. OK, now you have your liquid you have 2 options, store it in the fridge where it will keep for about a week or mix it with Molasses to stabilise the culture where it will keep for 6 months or more. To stabilise mix the culture 1:1 with molasses, so 1 litre culture to 1 Litre of Molasses gives you 2 Litres.....it's worth airlocking this too until the mix stabilises.

What's the point?

Excellent question :o) The more mundane uses for LAB include using it as an odour neutraliser if you happen to keep chickens etc - Mix 30ml per litre of water and spray around the coop to reduce the smell - Unblock drains - 15ml per litre and let it go to work over night and many more! For your growing needs however mix 30ml or so with every litre of your plant's water. The microbes will help cycle the nutrients in the soil making them more available to the plant! Add your LAB to compost - 30ml per litre and damp down every time you add to the pile or as you're layering up. The Lactobacillus will speed up decomposition and start to cycle the nutrients! Finally (and more excitingly), I mentioned earlier that LAB is the cornerstone of further processes that are highly beneficial to a gardener. For instance LAB can be used for Bokashi composting, no more need to buy bran for your indoor composting! If you've never heard of Bokashi, I'll cover it at some point. LAB can also be used to ferment plant material, for instance if you already add seaweed meal to your feeding regime, imagine if you could 'pre-digest' the nutrients held within the seaweed - making the non soluble elements readily available at application....with LAB you can. If you're a gardener familiar with the process of rotting comfrey or nettles in a bucket to annoy your plot mates, why not use LAB to break down the vegetable matter without the smell, and more importantly, without the risk of culturing the bad anaerobic bacteria. Using these principles it's basically possible to make your own organic liquid plant food for free and without losing friends or neighbours..... The last point for this post is probably my favourite - With LAB it's possible to create your own fish fertiliser (Fish hydrolysate) this in conjunction with your nettle/seaweed/comfrey/grass brews will give you the perfect base for making your own liquid organic fertiliser.... ...that's not bad for a little milk and help from a bacterium.

Foot notes - There should really be a sequence of pictures to go with this post, but frankly they weren't up to scratch. If anything needs clearing up drop me an email or comment below. - N.D