There’s a specific type of biomass fermentation called gas fermentation, which allows for the creation of edible protein out of thin air. When I first heard about it, it sounded a bit like magic. Turns out it’s done through growing Hydrogen-Oxidizing Bacteria (HOB) in a bioreactor. The inputs are:
- Hydrogen
- Oxygen
- Carbon dioxide
- Nitrogen
Are there any folks interested in this specific type of biomass fermentation? I know there are a number of companies in this space, with Solar Foods(🇫🇮) probably the most well known, but there's also Air Protein (🇺🇸), Farmless (🇳🇱) and Arkeon (🇦🇹). However, I've not seen anyone trying to do this open source in a home/kitchen lab yet.
@“Gerrit”#p17 It’s almost certainly my next port of call. I think it needs a lot of thought to mitigate the risk of hydrogen explosions though. Have you had any thoughts on nitrogen sources? I’m thinking urea might be nice…
The paper that I’m currently reading (mentioned in another thread) stated that 4 vol% O2 is optimal for the growth of C Necator, and that the lower explosion limit is 6 vol% O2 in excess of hydrogen gas, so that’s quite fortunate.
Using urea as a nitrogen source could be ... interesting 😄
I reposted Adrian’s questions in a Wave Bioreactor thread, but thought it would be good to discuss this one in general here, then we can pull the any conclusions relating to Wave Bioreactors back into that thread:
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@“Martin”#p42 What are the special requirements for HOBacteria?
OK, so what do we need to convert a Pioreactor to an electropioreactor? I’m thinking:
1. DC Power Supply (I understand Narcís is using 800 mA for a 1L bioreactor, so guess we’ll need ~ 16 mA. I presume linear would be best, and for video purposes I’d prefer one without a fan, so I’m currently looking at this Duratool D03232 - I know it will only resolve to 0.01 A so, we won’t be able to hit 16 mA, and accuracy will presumably not be great either, but everything I’ve found that could (and is fanless) costs at least 10x as much…
2. Anode - Narcís uses an anode made of Ti-MMO mesh (100 cm2, NMT electrodes, South Africa) - I wonder if [this would be close enough](https://amzn.eu/d/c4KBqs7)? Or might we need to find a rod to fit it into the 20ml reactor?
3. Cathode - Stainless Steel - what about [this coach bolt](https://cpc.farnell.com/duratool/d02007/stainless-steel-coach-bolts-m6x80/dp/FN02718?st=stainless%20steel%2080mm)?
4. 20ml vial cap - with liquid-in, liquid-out, gas-in, gas-out, cathode and anode ports, customised [from this](https://www.printables.com/model/546263-blank-pioreactor-24-400-vial-cap).
5. Hydrogen Oxidising Inoculum - [_wautersia eutropha_](https://nrrl.ncaur.usda.gov/cgi-bin/usda/prokaryote/report.html?nrrlcodes=B%2d2804) (see [_cupriavidus necator_](https://en.wikipedia.org/wiki/Cupriavidus_necator)), [_xanthobacter autotrophicus_](https://nrrl.ncaur.usda.gov/cgi-bin/usda/prokaryote/report.html?nrrlcodes=B%2d14836) or [_x flavus_](https://nrrl.ncaur.usda.gov/cgi-bin/usda/prokaryote/report.html?nrrlcodes=B%2d14838)?
@“Martin”#p55 I don’t know anything about electrochemistry, but it seems like what you need is a constant current source. While a bench top power supply can act as a constant current source, like you said it’s accurate enough at the size we need. It appears that we may need to use a potentiostat, so I would love to get some input from the folks over at IO Rodeo here!
@“Gerrit”#p56 Have you seen Narcís’ latest paper? I asked if we’d need a potentiostat like they used for their first paper, but he said they were using a regular <€100 bench power supply. Looking at the latest paper it’s cited as “a power source (IMHY3, Lendher, Spain)” - google’s not helping me with IMHY3, but theirs should in theory be 50x larger than we need anyway.
That said IO Rodeo's [Rodeostat](https://iorodeo.com/products/rodeostat) could be excellent if we do need better control. I had a great conversation with Will about their pH FeatherWing, which unfortunately in its current form wasn't set up for Raspberry Pi use. Fortunately though (since I also don't think we could fit a pH probe plus 4 ports and 2 electrodes in a 20 ml vial), Narcís mentioned that their pH is pretty stable other than when they add CO2.
Maybe we should do that paper in our first journal club instead?
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@“Gerrit”#p56 like you said it’s accurate enough at the size we need
I just noticed a typo - it should've said **not** accurate enough. I don't think a bench top power supply will be able to act as a constant current source in the range of 16mA.