Posted on by pez

Microbial Cellulose — 2 A2 Sheets Worth

44x18 cellulose sheet drying on clothesline

Back in mid September, we made a batch of Bacterial Cellulose in two 44″ x 18″ tray bioreactors, using Adam Korshid’s “blanco cellulose” medium (sugar, yeast and apple-cider vinegar in ratios carefully measured by eye and tongue).  About two weeks later, one of the cultures had essentially failed, but the other had blossomed with a vengeance, coughing up a giant, off-while pellicle that was about 3/8 inches thick and probably weighing a good 10 pounds.  For what it’s worth, it was also quite a smelly beast.  In fact, the smell largely motivated the timing of the harvest (kind of a “get-that-friggin-thing-outta-here” situation).  One unexpected benefit of the stench was that I was able to identify butyric acid as the main offender — so the absence tea in the culture seems to result in increased butyric acid production. Possibly a consequence of the low nitrogen content of the “blanco” medium?  It might be interesting to research the topic …

At any rate, the 44×18 sheet was ultimately dried and delivered to Ann Saintpeter as promised.  We’ll see what she prints on it, if anything.  While the sheet was drying, I discovered that you could kill the smell by dusting it with baking soda.  It also turns out I was late to that particular party — apparently baking soda is renown as an odor killer precisely because it forms salts with organic acids that tend to be some of the main components of many unpleasant odors.

The sheet ultimately dried to look very much like a giant, soft tortilla, complete with a dusty surface (courtesy of the baking soda).  It also ended up with some mild scorch marks, since I was trying to dry it in a hotel room, using the courtesy hair-dryer and iron.  If nothing else, the scorch marks helped with the tortilla-like appearance.

I’m currently embarking on a little experiment to study factors influencing cellulose production, including density of the substrate (i.e. how much sugar to hit the production “sweet spot”, so to speak) and substrate type (supposedly glycerin is the ultimate feed-stock).  If there are any results worth publishing, we will do so — possibly with hardcopies on microbial cellulose paper.

13 Replies to “Microbial Cellulose — 2 A2 Sheets Worth”

  1. so awesome, congrats Mike! this is really incredible stuff. can’t wait to write on some more of it.

  2. I have been doing some experiments on Kombucha Cellulose for about 3 months. Right now I am checking to see if I can stack sheets on top of each other and grow them together by adding a bit of sugar between the sheets (not submersed). 3 days into drying in there seems to be quite a bit of adhesion. Also I made a little fairy lamp by molding a 12 inch diameter circle of cellulose over a large light bulb and letting it dry. Kept its shape nice after breaking the bulb. I cut the the edge to make it look like a tulip and hot glued in a few LEDs Nice fairy lamp for the kids. To lighten a brownish hued culture I have used Hydrogen Peroxide with good results…I just shook up the dried culture with the HP in some tupperware. Took a day but it bleached out nice. the culture is still somewhat flexible but seems a little more brittle.

  4. Hello!

    That is a quite nice looking sheet you got there! I am very impressed with the size of it and how well it seemed to be growing. I am growing some cellulose myself and maybe you could give me some additional advice. send me an email if you get a chance, thank you!

  5. Hi Erik,

    My son did some research on this for a high-school project. It turns out that the “traditional” concentration of sucrose in kombucha recipes (about 1 cup per gallon) is nearly optimal. You can push it up to 2 cups, but at that point, the cellulose tends to trap un-catalyzed sugar in the cellulose, and contamination (fungus, mold etc.) starts to become a problem.

    So, 1 cup sugar/gallon, large flat container (the bigger the better, fill to, say 2″ deep), a nitrogen source (say, green tea), a b-vitamin source (yeast is good — the co-culture provides B-vitamins and ethanol, which the A. Xylinum like). A little ethanol and/or vinegar helps kick-start the process.

    This white cellulose eliminated the tea. You can substitute other nitrogen sources. I found that the eliminating the tea causes the results to be highly variable — not sure why.

    Photos of my son’s experiment are available on my google+ feed (mikehogan62) — search for “cellulose”.

  6. Hi, I’m a Jewellery Design student at Central St Martins college of Art, London, using this material for my degree collection. I’m experimenting with variables at the moment, was wondering if you had any further research you have conducted you could tell me about, or if you knew of any similar materials/ experiments I could conduct. I’m really interested in creating a sustainable, biodegradable material that is alive on the wearer. Any info would be much appreciated, as a design student with great curiosity of biology but lacking in the knowledge. Thanks so much, Rachel. (racheltrattles@yahoo.com)

    1. Hi Rachel. My son did a science project on the effect of sucrose concentration on the growth of microbial cellulose. The upshot was that the traditional concentration of 1 cup of sucrose per gallon is pretty near the “sweet-spot” for optimal growth.

      I think that the most interesting aspect of the cellulose that I grew in my post is the fact that it is nearly white. That sets it apart from microbial cellulose grown in tea. It is possible to make very white cellulose by boiling the pellicles in a weak sodium hydroxide or sodium carbonate solution. With practice, you can convert the cellulose to an almost perfectly clear gel, which will form a transluscent, white sheet when dried. However, I kind of like the off-white color of the cellulose that I grew using a medium of yeast and sugar with a touch of vinegar — it looks more natural, it’s simpler and it avoids the risk of weakening the fabric via hydrolysis of the cellulose. I will caution that the “tealess” cellulose is not that stable — sometimes the colonies thrive and sometimes they don’t. It’s not obvious what makes one batch work and another one fail. I presume that you adapt the “blanco” technique by using natural pigments that infuse into the cellulose, but I have never tried this.

      One other helpful hint — washing the pellicle in baking soda is a simple, effective way to kill most of the smell.

      I was playing around with the idea of using some sort of foil transfer technique to make an “alien” work of art, but I did not get too far with this. The basic idea is to run the material through a photo-copier to imprint a pattern (e.g. alien symbols) and then use heat to fuse gold foil to the laser toner. I did a quick prototype, but was not wowed enough by the result to try and perfect the technique.

      Wearable electronic jewelry on a bacterial cellulose substrate might be very, very cool (e.g. something like this: http://www.hive76.org/crafty-computer).

      At any rate, sorry to ramble. Best of luck and I’d be interested in seeing what you come up with.

  7. wow thanks so much for your help. Very excited to start shaping the material and seeing what I can do with it. So glad I came across this website! Will let you know what the finished collection looks like. Thanks again!!

  8. hi its me again! just wondering if you would be able to gibe me an idea of quantities of ingredients. I have one kombucha mother which im growing, but is it possible to combine the yeast, sugar, water and vinegar and green tea(?) to grow a cellulose without needing a mother kombucha scoby? if so what are the quanteties needed? i have live yeast, green tea, refined sugar and apple cider vinegar. thanks

  9. You have all the right ingredients. I would suggest that you make a large batch of tea (cold infusion works fine — making five gallons of hot tea is difficult and dangerous). Then add one cup of sugar per gallon of tea. I think that I 1/4 cup of yeast per five gallons of fluid and maybe a cup of vinegar (the vinegar mostly lowers the pH, which keeps out fungus etc.). You can even toss in a little ethanol (or not).

    You need to inoculate the culture somehow. There are a few ways to do this. Below is a partial list, along with some remarks on how it influences the final result.

    – Pull a “baby” off of the mother and drop it in your culture. The Mother will keep growing small “baby” pellicles indefinitely — they need to go somewhere — may as well go into the soup. One potential drawback to this technique — if you are trying to grow sheets, then the pellicle will wind up embedded as a lump in the sheet.

    – Take a pellicle fragment and homogenize it in a blender, then pour the homogenized fragments into the culture. This works pretty well and is probably the fastest inoculation method available (i.e. you will get an initial “skin” very quickly). The only drawback that I can think of is that the pellicle fragments tend to coalesce before the main “sheet” grows, so it can result in a discolored spot in the resulting sheet. If this is ok (or even desirable) then this might be the method you want.

    – Decant kombucha from a healthy culture into the reactor. There are normally enough bugs in the mix to get things started. The culture will get a slightly slower start, but the resulting mat will generally be much more homogeneous.

    I will assume that you are mainly trying to grow sheets, in which case the best reactors are large, flat plastic trays, filled with, say, 2″ to 3″ of medium. The reason flat tray work so well is that there is more surface area, so more oxygen diffusion into the culture, and that gives you faster growth.

    You should be able to grow a rather thick mat in three to five days. You can let it go longer (and it will get thicker, up to a point), but the growth rate starts to slow down (sugar is catalyzed, yeast starts to die, the mat starts to limit oxygen diffusion into the culture, the culture gets extremely acidic etc.).

    If you let the initial mat grow for three to five days, you can typically harvest it and then let the culture sit for another five days at which point you can usually harvest a second mat. This second mat will be a little different in texture, since the culture conditions are somewhat different. Typically, the second mat is smoother than the first, because the yeast in the second round are less active (hence less gas, hence a smoother sheet) The combined thickness of the two mats will be far thicker than a single mat from a 10 day culture — probably because the removal of the first mat lets oxygen diffuse into the culture, hence more total oxygen makes its way into the final product and more cellulose is produced as a result.

    The cultures are actually so “infectious” that you can make an exponentially increasing “factory” by making a reactor, growing a mat, then splitting decanted liquid from the culture between two reactors (and adding in fresh ingredients), growing two mats, etc, etc, After 10 generations you will have 1024 sheets growing simultaneously. After 20 generations you will have over a million sheets growing simultaneously etc.

  11. Dear Sirs,

    We are a trade company in Korea.
    One of our customers is looking for bio cellulose sheet for product of boi cellulose facial mask.

    If you can supply to this sheet, could you please introduce me ?

    Waiting for your reply.

    Y.N.Kang.

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