I have started some experiments using pioreactors. However, I have noticed that after removing the vial from its holder, taking a sample and reinserting it, the OD values change in an abrupt way (from 0.226 to 0.266). We have experimented with the same problems when using our custom minibioreactors, and we think it is related to minor differences in the surface of the vials.
Would it be possible to add some sort of 3D printed part to modify the current vial holder to implement a poka yoke system that forces the vial to be inserted in exactly the same position?
I’ve experienced this issue also, any sort of disturbance to the Pioreactor may result in an observable change in OD. You could easily add a protrusion to the vial cap, but given that you are unscrewing the vial cap each time, you would need some way of knowing that you were tightening it the same way each time. Or you could move to a square cuvette that would require a complete Pioreactor body redesign & significant cost increase in the vials.
Might I suggest than a much easier way would be to use a luer tip syringe and some submerged tubing to take your samples. Or, if you’re less concerned about contamination, use the g1/8 hole and a suitable pipette.
Your syringe solution is valid, however I work with alternative media, so I would need an extra hole (the room is intended for gas exchange through a 0.22 micron filter). Anyway, it’s nothing too difficult to do with the right drill bit, Peek tube, thermoresistant and self-leveling silicone and some know how
