COMPARATIVE STUDY ON THE LIPASE ACTIVITY FROM PLANT SOURCES, UNDER VARIOUS CONDITIONS OF pH, TEMPERATURE AND SUBSTRATE

Marcel AVRAMIUC

Abstract

The activity of the lipase from four different plant sources, under various conditions of pH, temperature and substrate, was analyzed in this paper to see which of these sources shows the highest enzyme activity. The lipase sources were represented by seeds, belonging to four plant species: sunflower, corn, pumpkin and soy, and as substrates for enzyme activity, the following refined oils were used: sunflower, pumpkin, soy bean, corn, peanut, walnut, almond and sesame. The activity of lipase was determined at 20ºC and 40ºC, at three different pH values (5.4, 7.4 and 8.2) for each temperature, and consisted in titrating (with a solution of KOH 0.01 N) fatty acids released from oils by lipase, in a certain time interval. According to the experimental data, the lipases deriving from sunflower, corn, soy and pumpkin seeds, registered the highest values of activity at pH 5.4 (at 20°C or 40°C). As compared to the other three sources, the values of sunflower seed lipase activity were significantly higher (P<0.05) in the following oils: sunflower, soybean, peanut, corn and walnut. At the same pH 5.4, the corn caryopse lipase recorded the highest activity on walnut oil, at 20°C, and on corn oil, at 40°C, the pumpkin seed lipase on walnut oil, at 40°C, and the soy bean lipase on walnut, at 40°C. A high content of oleic acid, but especially of linoleic and linolenic acids within oils used as substrate, caused an increased activity of lipase in sunflower seeds.

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