The pretreated yellowfin tuna spleen extract was used as feed in ultrafiltration for recovery of protease. The combined impact of crossflow rate and gas sparging on critical flux, limiting flux and selectivity was studied by a total recycle mode using a hollow fiber membrane with molecular weight cutoff 30 kDa. The critical flux varied from 28.8 to 44.2 L/m(2) h and limiting flux varied from 34.3 to 52.4 L/m(2) h while crossflow rate increased from 17.55 to 69.98 L/h without gas sparging. A low gas injection factor of 0.15 could improve critical and limiting flux significantly comparing to that without gas sparging. Higher gas injection factors varied from 0.30 to 0.61 did not give remarkable improvement of both critical and limiting flux. The benefit of increasing crossflow rate to enhance critical and limiting flux was great when g-as sparging did not applied. Selectivity of ultrafiltration process was increased with increasing permeate flux at subcritical condition and critical flux condition. It became insensitive to the flux and crossflow rate at limiting flux condition when gas sparging was not applied. Gas sparging gave negative effect on soluble protein and peptide transmission and resulted in the decay of selectivity at subcritical condition and critical flux condition. The selectivity at limiting flux condition with gas sparging was not sensitive to gas injection factor. (C) 2008 Elsevier B.V. All rights reserved.