Modeling Vapor Phase Water Droplet Extraction of Proteins from the Medium of an Air Fluidized Bioreactor

It has been previously observed that in a semi-solid air fluidized bed bioreactor, with a potato providing the sugar substrate, and defined media providing the minerals and vitamins [2], certain proteins produced by the bakers’ yeast growing on this aerated semi-solid are carried out of the bioreactor by the effluent air stream [3]. Since proteins can be separated from solution in traditional submerged fermentation processes at their isoelectric points by bubble fractionation [4], it seemed reasonable to propose that the isoelectric point may be an important variable in the air fluidized bed protein synthesis and separation process [5–7], as well. It turned out that for an initial 100 mg/L invertase concentration in an experimental model batch system (a shake flask), the separation between the air phase (or more precisely, micro-water droplets in the air phase) and the bulk liquid phase is not affected by changes in the initial pH concentration over the range 2 < (pH)₀ ≤ 8. This indicated that the separation between the media surface and the water droplet surface in the fluidized bed may not be sensitive to the bulk liquid pH level [8].