Evaluation of tangential filtration methods for the recovery of scleroglucans

Two methods of tangential filtration, axial filtration and cross-flow filtration, were tested on scleroglucal broths. These methods were compared to conventional straight-flow filtration using the same media with 5-..mu..m pore size membranes. The axial filter at a differential pressure of 5 psi provided higher permeate fluxes after 6 min of filtration time and caused less polymer rejection by the membrane as measured by filtrate viscosity. Fluxes obtained using the axial filter fitted wth a 125-..mu..m screen separated about 90% of the biomass from the diluted culture broth with no apparent polymer rejection as measured by filtrate viscosity. Both cross-flow and axial filtration methods gave higher fluxes after a 6-min filtration time than flat-plate filtration when used to polish the axial-flow screened filtrate using 5-..mu..m membrane. At 5 psi differential pressure, less polymer rejection was observed with axial filtration of the prescreened feed than with the flat-plate filter. In addition to higher flux, tangential filtration methods produce a concentrated biomass stream which has the potential for use as an animal feed component.