Comparison of methods for extracting Kafirin proteins from food-grade sorghum cultured in a Mediterranean environment

Authors: PONTIERI, PAOLA - Istituto Di Bioscienze E Biorisorse-Uos Portici-cnr; TROISI, JACOPO - University Of Salerno; Bean, Scott; Tilley, Michael - Mike; DI SALVO, MARCO - Dipartimento Di Scienze E Tecnologie Ambientali; BOFFA, ANTONIO - Istituto Di Bioscienze E Biorisorse-Uos Portici-cnr; PIGNON, DOMENICO - Istituto Di Bioscienze E Biorisorse-Uos Portici-cnr; DEL GIUDICE, FABIO - Bioteam Laboratory; ALIFANO, PIETRO - Dipartimento Di Scienze E Tecnologie Ambientali; DEL GIUDICE, LUIGI - Istituto Di Bioscienze E Biorisorse-Uos Portici-cnr

Submitted to: Australian Journal of Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2019
Publication Date: 8/30/2019
Citation: Pontieri, P., Troisi, J., Bean, S.R., Tilley, M., Di Salvo, M., Boffa, A., Pignon, D., Del Giudice, F., Alifano, P., Del Giudice, L. 2019. Comparison of methods for extracting Kafirin proteins from food-grade sorghum cultured in a Mediterranean environment. Australian Journal of Crop Science. 13:1297-1304. https://doi.org/10.21475/ajcs.19.13.08.p1695.
DOI: https://doi.org/10.21475/ajcs.19.13.08.p1695

Interpretive Summary: Isolated sorghum (Sorghum bicolor) storage proteins (kafirins) have been successfully used in a number of bio-materials including adhesives, films, micro-particles, fibers, and biological scaffold material. Comparatively little research has been conducted on how isolated kafirins could be used in foods or hydrolyzed for bioactive peptides. Thus, the aim of this study was to investigate extraction methods for sorghum kafirins to identify the solvent with the least toxicity while maintaining a high extraction rate from sorghum grown in Mediterranean area. Use of acetic acid or ethanol based solvents had similar protein recoveries, but showed some differences in protein composition. These differences may cause functional differences when used as food and warrant further studies. This research provides information to support new uses of sorghum proteins and provides additional knowledge of sorghum proteins, an important grain quality component.

Technical Abstract: Isolated sorghum (Sorghum bicolor) storage proteins (kafirins) have been successfully used in a number of bio-materials including adhesives, films, micro-particles, fibers, and biological scaffold material. Comparatively little research has been conducted on how isolated kafirins could be used in foods or hydrolyzed for bioactive peptides. Thus, the aim of this study was to investigate extraction methods for sorghum kafirins to identify the solvent with the least toxicity while maintaining a high extraction rate from sorghum grown in Mediterranean area. Five different extraction methods were compared including 1) aqueous ethanol containing NaOH and sodium metabisulfite, 2) glacial acetic acid, 3) aqueous ethanol with sodium metabisulfite, 4) aqueous ethanol at acidic pH, and 5) alkaline pH alone. The protein contents of the kafirin isolates obtained by the five methods ranged from 49.76% to 56.83%. Reversed phase-HPLC chromatograms revealed substantial variability in the various kafirin patterns among the extraction methods tested. Conversely, size exclusion chromatography of the kafirin samples did not show a high degree of variability among the methods. Likewise SDS-PAGE electrophoretic patterns of the five respective kafirin samples showed essentially the same band profiles but with different concentrations among kafirin extraction methods. Surface hydrophobicity of the kafirin isolates varied considerably with isolates extracted with glacial acetic acid and aqueous ethanol plus sodium metabisulfite the most hydrophobic as indicated by hydrophobic dye binding.