enzymatic hydrolysis, performed under batch processing has several disadvantages including low productivity. To overcome some limitations, an enzymatic membrane reactor (EMR) has been proposed Pre-hydrolysis possibly plays an important role in EMR performance. Therefore, the effects of pre-hydrolysis were investigated in an enzymatic reactor on the membrane performance of a low molecular weight peptide produced from Nile tilapia skin gelatin containing 4% weight per weight alcalase at 50 oc pH 80. The gelatin solution was pre-hydrolyzed for o. 15. 30 or 60 min before passing through the l kDa molecular weight cutoff ultrafiltration membrane. The permeate flux, protein conversion, capacity, productivity, fouling resistance and angiotensin-I converting enzyme inhibitory activity were investigated. the results showed that the pre-hydrolysis time had a significant effect on the gelatin solution viscosity permeate flux and fouling. The results also indicated that pre-hydrolysis could noticeably increase EMR performance. A pre-hydrolysis gelatin solution pre-hydrolyzed with alcalase for 60 min was required to enhance the EMR performance during the production of low molecular weight peptides from Nile tilapia skim gelatin