Chemical Modification Of Native Proteins For Enhancing Their Biological Activities

Three legume proteins, soybean protein isolate (SPI), broad bean protein isolate (BPI) and chickpea protein isolate (CPI), were esterified to different extent by methanol. The esterified proteins were analysed for solubility, emulsifying and foaming properties at a pH range of 2-10. These functional properties were changed in the esterified proteins compared to the native ones. The magnitude of change was depended on the extent of esterification and the nature of the modified protein. Emulsifying activity and stability of esterified legume proteins at the acidic pH-range of 2-6 were generally higher than the corresponding native proteins. The foam activity and stability at the pH-range of 2-6 were generally higher compared to the corresponding native proteins. An improvement was associated with the degree of solubility, the enhanced degree of esterification and the nature of the used protein. Molecular weight of soybean protein isolate subunits ranged between 160170 to 92680 Daltons, molecular weight of broad bean protein isolate subunits ranged between 50415 to 100036 Daltons and molecular weight of chickpea protein isolate subunits ranged between 16750 and 106400 Daltons. SDS-PAGE of native and esterified legume proteins represented exchanges in molecular weights between native and modified proteins. Urea-PAGE of native and esterified legume proteins represented exchanges in charge between native and modified proteins. Gel-IEF of native and esterified legume proteins represented variation in isoelectric points between native and modified proteins. The methylated legume proteins inhibited the growth of gram negative bacteria (Escherichia coli and Pseudomonas aeroginosa (and gram positive bacteria (Bacillus subtilis and Staphylococcus aureus).