|Fractionation of wheat bran albumins through size exclusion chromatography (SEC)|
G. CHAQUILLA-QUILCA (1), R. Balandran-Quintana (1), J. Luna-Valdez (1), J. Mercado-Ruiz (1), A. Mendoza-Wilson (1), G. Ramos-Clamont Montfort (1), J. Azamar-Barrios (2) (1) Centro de Investigacion en Alimentacion y Desarrollo, A.C., Hermosillo Son., Mexico; (2) Centro de Investigación y Estudios Avanzados del IPN-Unidad Mérida, Mérida Yuc., Mexico.
The wheat bran has significant amounts of underutilized proteins, representing areas of opportunity for innovation and added value. Traditionally these proteins are extracted in bulk by alkaline extraction, followed by acid and heat precipitation and occasionally assisted by cell wall enzymes, an expensive method and chemically aggressive. However, is possible obtaining concentrates of the water soluble proteins, or albumins, which after some fractionation step are susceptible of being used in sophisticated applications such as nanotechnology. In this work, by water extraction, dialysis and liophylization, it has been obtained a concentrate of wheat bran albumins (CWBA) with 45 % protein (d.b). Three bands of 15, 52 and 90 kDa were visible in electrophoresis native gels, whereas in SDS-PAGE gels there were 9 bands (7 to 84 kDa), indicating that the CWBA has 3 proteins conformed by several sub-units. The CWBA was fractionated by size exclusion chromatography (SEC), from which two non-protein fractions and 4 protein fractions were obtained. The protein fractions had molecular weights of 102, 58, 15 and 6.5 kDa, respectively, determined by comparing their elution volume with those of SEC protein standards. The analysis of the fractions for monomeric sugars (HPLC-PAD) and by UV-Vis and FTIR spectroscopies suggests that the non-protein fractions contain phenolics, arabinoxylans and/or arabinogalactans. On the other hand, in the 58 kDa fraction there was a significant activity of the enzyme polyphenol oxidase (PPO), an interesting fact because the current purification of PPO by chromatographic methods is a laborious process; here is demonstrated the possibility of being undertaken in a few steps, although deserves further studies. To the best of our knowledge, this is the first report on separation of wheat bran albumins by SEC.