The pH stability and the influence of salts on the activity of a milk-clotting enzyme from F. johannis latex

Numerous studies have been carried out to replace calf rennet with other milk-clotting proteases because of limited supply and the high price of calf rennet. The latex of Ficus johannis (Moraceae), rich in milk-clotting proteases, have been traditionally used as a plant coagulant for cheese-making. No systematic study on thecharacterization of F. johannis milk-clotting protease has been conducted so far. The purpose of this study was to investigate pH stability and effect of salts on the activity of the purified protease. The enzyme was extracted from the latex of F.johannis and purified viacation exchange chromatography.The proteolytic and milk-clotting activity of the protease was evaluated using casein and skim milk as a substrate, respectively.The pH stability determined by examining the residual activity after incubating the protease in different buffers with pH ranging from 3.0 to 11.0. The effect of different concentrations (0–3 mol/L) of NaCl and CaCl2 ions on the enzyme activity was determined.The molecular mass of the purified protease was estimated to be 25 kDa by SDS–PAGE. The results showed that the protease was almost completely active in the presence of high salt concentrations.The protease is stable under a broad range of pH between (4.5-9.5),maintaining almost its complete activity. F.johannis protease was efficiently active under different salts concentration and in a wide range of pH. The purified protease can be suggested as a suitable alternative to commercial calf rennet in the dairy industry.

کلیدواژه ها:

Ficus johannis ، Milk-clotting ، Enzyme activity ، pH stability