Specific Activity of Pineapples Bromelain Extracts at Different Purification Stages Obtained from Different Agro-Ecological Zones of Thika Region, Kenya

Abstract

Aims: The use and specific activity of bromelain from pineapples are limited by the presence of contaminants. The aim of this study was to determine the enzymatic activity of bromelain in crown, peels and stem at different purification stages leading to the production of lyophilized bromelain. Methodology: The pineapples were obtained from the upper, mid and lower agro-ecological zones (AEZs) of Thika region, Kenya. The pineapple extracts were purified in sequential stages; centrifugation, ammonium sulphate precipitation, dialysis, to molecular exclusion chromatography and lyophilisation. Protein concentration and bromelain activity were determined after each purification stage. Results: The mean specific activity at different purification stages of crown bromelain from upper AEZ ranges between 47.88-218.62 U/mg, for mid AEZ specific activity ranges between 49.98-220.24 U/mg, while in the lower AEZ 55.20-228.11 U/mg and increased significantly (p<0.05) with every purification step. The mean specific activity of bromelain in the crown was highest (p<0.05) in pineapples sourced from lower AEZ. The ranges of activity for bromelain from the crown were: upper AEZ 47.88-218.62 U/mg, mid AEZ 49.98-220 U/mg, lower AEZ 55.20-228.11 U/mg. Secondly, the ranges of activity for bromelain from the peels were: upper AEZ 49.98-220.24 U/mg, mid AEZ 52.19-247.86 U/mg, lower AEZ 54.17-234.59 U/mg. Finally, the ranges of activity for bromelain from the stem were: upper AEZ 41.06-180.80 U/mg, mid AEZ 42.79-214.45 U/mg, lower AEZ 49.11-224.87 U/mg. Conclusion: The mean specific activity of bromelain in the pineapple parts was significantly (p<0.05) higher in pineapples sourced from lower AEZ compared to those from other zones. In conclusion, the study has shown that the purification of pineapple extracts increased the bromelain specific activity.