Expanded bed adsorption for recovery of patatin from crude potato juice

An expanded bed adsorption process was used to isolate patatin possessing esterase activity, from a crude juice of potato tubers. Patatin is the major storage protein of potato tubers and is released in ample amounts in the processing effluent during starch milling. We employed mixed mode affinity resins, where the binding depends primarily on the pH, and is almost independent of the ionic strength. From a library of mixed mode chemistries involving both charged and hydrophobic functions, we screened for ligands with binding specificity for patatin. The dynamic binding capacity of two high density (1.4-1.5 g ml(-1)) patatin-binding agarose-glass resins in response to change of linear velocity (85-230 cm h(-1)) was tested in packed (25 ml) and expanded (250 ml) column modes. The column operation included a loading step at low expansion; H/H-o similar to 1.2. Adsorption from crude juice at pH 7.5, retained patatins up to a breakthrough level of 50%. The eluate fraction at pH 3.5, now effectively stripped from the pigments, provided a 2.5-fold enzyme enrichment and produced 4 g protein per cycle. Column productivity was 122 kAU L-1 h(-1). The study, using potato juice as model feedstock, demonstrated the feasibility of expanded bed-recovery of potentially valuable proteins from plant biomass.