Enzymatic hydrolysis of lupin (Lupinus angustifolius) protein : isolation and characterization of bioactive peptides

Blue lupin (L. angustifolius) is one of few sweet lupin species that is most commonly grown in Australia as soil nitrogen fixing crop. Australia is the largest producer and exporter on sweet lupins in the world. Despite the fact that lupin is rich of protein and fibre, and the lupin based foods offer several health benefits, the grain is mostly used for animal consumption. Hence, it is a low priced commodity. It is therefore; very beneficial to demonstrate the possibility of deriving nutraceutical, functional and therapeutic agents from sweet lupin grain/flour that is most abundant in Australia. Research in this direction will benefit Australian farmers, food industry as well as consumers. This project aims to derive bioactive peptides from lupin protein. It is well known that bioactive peptides can be derived from many food proteins (both animal and plant sources); such as milk, eggs, cheese, meat, fish, soy, rice, wheat and legumes. The process of protein hydrolysis to produce bioactive peptides is of several types, namely, (i) gastrointestinal digestion by digestive enzymes (ii) fermentation by microbial enzymes and (iii) in vitro hydrolysis by commercial enzymes. Many proteinases such as alcalase, trypsin, chymotrypsin, pancreatin, pepsin and flavourzyme have been employed in the literature to produce important bioactive peptides from food proteins. This study aims to: • Enzymatically hydrolyse sweet lupin protein using pepsin, pancreatin and flavourzyme (lupin hydrolysates). • Separate the lupin hydrolysates by molecular weight cut-off (MWCO) membrane. • Further purification of MWCO fractions by bioactivity guided purification methods. • Size exclusion chromatography (SEC) is used in this research for bioactivity guided purification. • Several bioactivities were determined at different stages of purification. These include; antioxidant, immunomodulatory, ACE inhibitory and antimicrobial activities. • The thesis also aims to evaluate the MRI contrast potential of bioactive lupin peptides isolated in this research