If you’ve been wondering why we use Wernher the yeast propagator, here it is. With this system we can make almost 50% yeast by volume! After centrifuging this is kind of hard to see, so here’s a cold crashed sample. One run from Wernher keeps us going for over 2 months! #vodkascience #wernher #drinkicd #yeast #beast (at The Lab at The City Foundry)
Ever wonder how we make the yeast beads for our immobilized cell bioreactors? We wish we could say it’s simple, but we’d be lying…
- It all starts with dry alginate powder
- the alginate gets dispersed into sterile hot water. Both “sterile” and “hot” are key here. The air bubbles are removed from the mixture and the alginate is chilled overnight.
- we then mix in (lots of!) yeast and stir it up really well to make a homogeneous mixture. This part looks really cool as the clear alginate swirls with the beige yeast.
- the yeast + alginate mixture is loaded into a sterile pressure tank and then extruded out of the emitter head that Zac made in the shop.
- The droplets fall one by one from the emitter (at about 100 per second) and fall into a sterile bath of 3.5% calcium chloride. This turns the liquid mixture into a gelatinous ball. This happens because the calcium replaces the sodium ion in the alginate making the alginate fibers go from smooth to something resembling velcro.
- The gelled bead is washed in a couple of baths with a final soak in a sucrose solution to wash out any calcium chloride and to “wake up” the dormant yeast cells.
- The final yeast beads are (literally) ladled into the waiting, freshly sterilized bioreactor. In this gelled state, the beads are very porous and are actually more like a mesh sphere than a solid rubber ball. This lets sugar flow into the bead, alcohol and carbon dioxide to flow out, but the yeast are stuck inside (It’s cool, they love it in there)
- The new bioreactor is loaded into our reactor room and hooked up to the system. These beads will last about 2 months before the whole process starts again.