Reserch For Extraction Method Of Bromelain From Pineapple Peel

This paper mainly studied the technique of bromelain extracting from pineapple waste by ammonium sulfate precipitation combined with ultrafiltration enrichment.First, the study showed that ammonium sulfate liquid addition was superior to solid in the process of bromelain extracting from pineapple peel extraction solution by ammonium sulfate precipitation; activity recovery of bromelain climbed up first and then declined with the pH value increased, and it was maximum for83.6%when the pH of the pineapple peel extraction solution was7; the activity recovery of bromelain increased first and then decreased with the ammonium sulfate concentration increased, and it was maximum for83.6%when the saturation of the ammonium sulfate was40%; in the range of experiment temperature, the activity recovery of bromelain increased first and then decreased with the temperature rose, and it was maximum for86.9%when the temperature of the pineapple peel extraction solution was20℃; the activity recovery of bromelain lifted first and then descended with precipitation time prolonged, and it was maximum for89.2%when the time of precipitation was60min.Second, the paper studied concentrating bromelain by ultrafiltration method. The result indicated that activity interception rate of bromelain was94%when using20KD ultrafiltration membrane, the ultrafiltration retentate should be collected, the activity interception rate was10.3%when using100ultrafiltration membrane, so that the ultrafiltration permeate should be colle the activity recovery rate of bromelain was gradually increased with centri speed increased, and it was89.3%kept the stable when the speed was up to8000rpm; To the20KD membrane, permeation flux was increased gradually and then decreased with operating pressure increased, and it reached5.57L·m-2-h-1when operating pressure was0.35MPa; To the100KD membrane, permeation flux was increased gradually and then decreased with operating pressure increased, and it was7.69L·m-2·h-1when operating pressure was0.25MPa; the ultrafiltration membrane’s permeation flux was gradually decreased with the using time increase whether it was processed or not, meanwhile, the activity interception rate of bromelain was gradually decreased; the permeation flux and the activity interception rate of bromelain were recovered to some degree when the ultrafiltration membrane was washed by pure water in low-pressure turbulence and then soaked in acid-base solution.Third, the study indicated that addition of L-cysteine, sodium benzoate, EDTA or vitamin C could improve the activity recovery of bromelain in the extraction process by coupling ammonium sulfate precipitation with ultrafiltration method. Among the additives above, L-cysteine had the greatest impact, the activity recovery of bromelain was maximum for112.5%when the concentration of L-cysteine was0.6mg/mL; the activity of bromelain was stabilized when the concentration of EDTA and sodium benzoate were0.5mg/mL; although vitamin C addition resulted in a low effect on bromelain activity recovery, considering it was much cheaper than the others, it should be used in bromelain extraction; the bromelain activity was3944.0U·g-1with88.6%activity recovery in the ultrafiltration operation as:dissolving the bromelain precipitation, ultrafiltrating and collecting the permeate by using100KD ultrafiltration membrane under0.25MPa, ultrafiltrating and collecting the ultrafiltration retentate by using20KD ultrafiltration membrane under0.35MPa; the collection was freeze-dried; finally, the total extraction rate of bromelain was0.228%.