Effects of pH and ionic strength on microfiltration of C-glutamicum

The effects of pH and ionic strength on microfiltration of Corynebacterium glutamicum (C. glutamicum) were evaluated. The filtration performance was c haracterized by the specific cake resistance (alpha) calculated from measur ement of dead-end filtration flux using Ruth's equation. When the pH of the cell slurry was adjusted from 6.3 to 2.0, alpha decreased by a factor of 5 which meant that the total flux was improved five times; the effect of ion ic strength was much less. Measurements of zeta potential and hydrophobicity showed the cells to be mo re hydrophobic and have lower surface charge at pH 2 than at neutral pH. Mi croscopic observation of cross-sections of the cell cake layer showed cells aggregated at pH 2, but not at pH 5. The aggregation behavior is consisten t with the reduction of surface repulsion at pH 2 and the larger voids betw een aggregates account for the larger flux. (C) 1999 Elsevier Science B.V. hll rights reserved.