It looks like it, anyway.
That’s why my fellow catalyst is calling this the “Hannibal Lecter Project” 🙂
The stuff that looks like skin is actually cellulose – the same stuff (more or less) that paper, cellophane, rayon and cotton are made from. Here it’s home to a colony of bacteria (mostly acetobacter) and yeast that live in happy harmony atop a brew of sweet and sour tea, with the bacteria pumping out strands of cellulose about a hundred-thousandth of a millimetre thick. And it’s reported that the bacteria can produce about their own length in this fibre every hour or two.
I’m delighted and excited by how quickly the pellicle (the cellulose-rich “skin”) has been growing, so here’s a little photo-diary of the project so far.
This is the established pellicle in a bit of a previous batch of kombucha, which provides the micro-organisms and acidity required to start the new culture. This pellicle is sometimes called the “kombucha mother”, from which a “baby” forms atop the new culture. I am chuffed with how fabulously organ-like it looks! You can see here how it’s made up of a number of thin sheets that stack together: some of this layering is due to successive “mothers” and “babies”, but formation also seems to happen in cycles in each culture, as you’ll see below.
Hearty thanks to our generous Culture Club contact for getting us underway with the source material!
And this is what getting underway looked like:
And here’s the second of our cultures, bought from a supplier in Darwin:
Just a few days after starting the culture, a thin film of cellulose (and microbes) was beginning to appear atop the brew.
And a week or so later, it had grown to this!
At about the two-week mark, it had reached about 10mm thick. You can see here the layers I mentioned above – each about 1mm thick – suggesting it gets built in cycles. Cells are just like more complex organisms, in that they have a built-in “clock”; however, it could also be variations in temperature causing the different production rates.
The three cultures we have so far are each behaving a little differently, with the stuff we bought via mail order looking nice but growing more slowly. The rather splendid-looking “pancake” formed out of the litre or so of excess liquid I scooped out of the big 18 litre batch; this was a great surprise, because it had no “mother” in it, apart from whatever tiny things might have been swimming in the liquid at the time.
Two weeks ago, I decided it was time to try “passaging” the culture (that’s what we call it in cell culture, when you take a portion of the culture and move it to a new home that has more room to move; splitting your culture from one flask into multiple flasks also lets you grow a lot more cells). We want to work up to large enough quantities to use the pellicle material as a kind of textile, so expanding the culture is a priority.
So I brewed up some fresh tea and performed a little surgery: a pellicular biopsy, if you like 🙂
And three days later, it was already starting to form an ever-so-slight film on top. This was a good sign of a robust process, because I deliberately made it difficult for the microbes by not giving them any of the “ripe” brew like one normally would. Instead, I just added vinegar to drop the pH to friendly levels, and relied on the tea, sugar and the microbes themselves to provide everything else. This one’s still growing more slowly than others, but it’s working nonetheless.
When playing with the cultures, I have been really impressed by how rigid the pellicle is – even the thin one shown at the top here is quite stiff. Although this surprised me, it actually fits with the microstructure shown by electron microscopy – an extremely fine meshwork of inter-weaving fibrils. Although the fibrils themselves are flexible, because there are so many and because they’re tangled over one another, they don’t easily move, and which makes the material stiff, strong and really difficult to cut!
It will be jolly interesting to see what it’s like once we get it out of the “vats”! I started one a few days ago, and it looks to be working nicely. More photos soon.
One last aside: another type of fermentation in which acetobacter make a cellulose-rich pellicle is in turning wine into vinegar. The pellicle in this case has been known as the “vinegar plant” or “mother of vinegar”. There’s a group at University of Western Australia who have recently started some similar textile-related experiments using this material.