Comparison of Different Protocols of Gradient Ammonium Sulfate Fractionation of Antibacterial Proteins/Peptides from Clarias gariepinus Wastes

In this study, gradient ammonium sulfate [(NH4)2SO4] precipitation technique was employed to extract antibacterial proteins/peptides from C. gariepinus wastes. 20, 40 and 60% were respectively used as initial saturation of (NH4)2SO4, then some indexes of crude proteins/peptides obtained at 80 and 100% saturation (NH4)2SO4 were compared. The yield of crude extracts obtained at 80% saturation (NH4)2SO4 was the highest when the material was precipitated initially at 60% saturation (NH4)2SO4. However, the yields of the fractions at 100% saturation (NH4)2SO4, precipitated initially at 20%, 40% and 60% saturation (NH4)2SO4, respectively, didn’t show significant differences. All of crude extracts had inhibitory activity against A. hydrophila, E. coli and S. aureus. The extracts obtained at the same saturation didn’t display obvious different patterns on the SDS-PAGE gel. Based on the results above-mentioned, we proposed that 60% saturation (NH4)2SO4 could be used as initial saturation in gradient (NH4)2SO4 fractionation for obtaining antibacterial proteins/peptides from C. gariepinus wastes.