The concept of a disk that alternately soaks the organisms
in nutrient medium and exposes them to air has been used for treatment
of wastewaters for many years. The design encourages sloughing of the organisms,
and waste streams are usually very dilute compared to industrial fermentation
media.
You can experiment with this applet to see what spacing of disks looks
like. You must leave room for the cellulose pellicle to form, but you want
as many disks as possible.
You can appreciate the spacing problem better from this animated applet. It shows an end view of the hopper and disks and an frontal fiew of four disks. There could be dozens of disks in a large commercial unit. Note that we start with a disk with enough growth to fill the plastic support, and its growth eventually fills up the space. This is bad operation.