This year I’m working on a thesis at VUB (Brussels) experimenting with bacterial cellulose, evaluating wether it could be suitable for use in tensile architecture. I will share my experiments and findings in this forum throughout the year so that everyone can follow what happens, learn from it and give me input
The first large part is focusing on mechanical strength. I will test the tensile strength of the plain material, will look into how seams can be created and what their strength could be and I will also look at composites, combining the growth of the BC with another material in order to enhance its strength.
I will write this post as a sort of chronological logbook on what I’m doing, trying to remain concise, and see how it works out. (Input on how I could improve this post is always welcome too!)
sidenote: I work in lab environment with autoclave, laminar flow and a 30°C growing room.
(I have a recurrent struggle with a contamination. If you have had this too and think you could be of help, please continue reading! )
time-based objective: have materials ready for testing by the end of december.
I started out just growing BC (without any real BC experience, but under supervision of Elise, also active in this forum, I thought it would work out) from the mother cultures I had from Elise, hoping to make large sheets quite quickly but it isn’t really working out at the moment.
The mothercultures of Acetobacter Xylinum were grown following this recipe from biohack academy.
1.First growing attempt
I started two batches in large bottles which were easy to seal with Parafilm. After two days already a surface layer was developing. Unfortunately it was a contamination. Threw it away after 10 days, it grew quickly in the beginning and then stagnated.
9 days growing (contamination)
2.Second growing attempt
I tried a larger batch in an IKEA box, here also after 2 days already a contamination was visible (see pic). Unfortunately it could not be autoclaved so I had to sterilise it with Ethanol before/while going into the laminar flow. The sealing was not optimal as well, had to close it all around with Parafilm but got some holes.
3 days of growing (contamination)
after two failed growing attempts I was a bit worried and curious about what that contamination was about.
- Contamination already present in recipients - bad sterilising
- Contamination already present in mother culture
- Contamination from the warm growing room - bad sealing
3.Third growing attempt - mother and feedstock growing comparison
I scaled down again to see if growing a small batch would even work. I directly grew different types of 200 ml batches to be able to compare 4 methods:
- 2 mother cultures (One original kombucha + one purified Acetobacter Xylinum mother)
- 2 feedstock recipes (One DIY recipe from this forum + one optimised, mentioned before)
criscrossing them gives 4 combinations, made 3 batches to have some more consistent results.
12x 200ml batches - day 0
This gave some interesting results:
12 days of growing
We can conclude:
The optimised recipe from biohack academy works very well, developing a homogeneous and plain sheet of BC, growth of about 5 to 8mm in 12 days
For some reason the DIY recipe with kombucha mother didn’t work at all
Only one batch was contaminated, showing also a darker colour of liquid. What does this mean…?
After some comments I learned that actually the optimised biohack recipe which isolates AX bacteria makes it possible to grow this very pure cellulose layer, while also making it more vulnerable for contaminations.
4.FIlter and composite test
Simultaneously with (3.) I grew 4 other batches to check wether there would be contamination in a medium recipient (larger than 200ml flask but smaller than IKEA box) with another filter type. I used two of them to do a first test on growing composites.
4a. filtertest: again both batches contaminated.
filtertest after 5 days, contaminated
4b. composite test: Semi contaminated, semi BC.
I tought this one had the least chance to work, since it was difficult to remain clean. I made a small construction to be able to tension the Hemp net in the box, so that the BC would grow on a ‘pretensioned’ net.
start: other filters + hemp net stretched at level of liquid surface
growth 3 days: contamination?
Took out after 5 days - left: both BC and contamination in hemp net - right: cleaned sheet
Dried sheets of composites: The BC is very thin and transparent, but it seems to keep all the fibers in place. Will continue trying this, maybe with a more dense fibre net (someone ideas for other materials?), also will have to look into how I can keep the material at the surface while pretensioning it + keeping everything sealed.
dried sheets of BC and hemp
haven’t updated this for a long time.
I have had multiple other attempts since november, a lot of them contaminated (looks like Kahm yeast that someone commented to me), some of them worked!
I’m adding a post on another test I did on trying to grow/create SEAMS, a subject in BC that really intruiged me: BC - creating seams between cellulose sheets
And another post on post-processing of BC sheets for mechanical purposes: BC post-processing mechanical comparison protocols
(this text is a logbook of my work, things will be added through time)
If someone is interested in spending some time reading more on what I’m doing, in this google drive link I placed a pdf of my WIP (beware, very WIP!!) writing. Also not everything I did up untill now is included yet, but comments are of course very welcome.
Thank you for reading me!
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Master Thesis by Bastien Damsin, Under supervision of Elise Elsacker, Prof. Lars De Laet and Prof. Eveline Peeters / Vrije Universiteit Brussel / Department of Architectural Engineering and Bioengineering Sciences.