title: Physicochemical properties of β and α'α subunits isolated from soybean β-conglycinin.
abstract: Soy protein has shown great potential for use in biobased adhesives. β-Conglycinin is a major component of soy protein; it accounts for 30% of the total storage protein in soybean seeds. β-Conglycinin was isolated and purified, and its subunits' (β, α'α) physicochemical and adhesive properties were characterized. Crude β-conglycinin was isolated from soy flour and then purified by the ammonium sulfate precipitation method. The α'α and β subunits were isolated from the purified β-conglycinin by anion exchange chromatography. Yields of α'α subunits and β subunits from 140 g of soy flour were 1.86 g (1.3%) and 0.95 g (0.67%), respectively. The minimum solubility for α'α subunits, β subunits, and β-conglycinin occurred in pH ranges of 4.1-5.4, 3.5-7.0, and 4.8-5.3, respectively. Transmission electron microscopy showed that the β subunits existed as spherical hydrophobic clusters, whereas α'α subunits existed as uniformly discrete particles at pH 5.0. Differential scanning calorimetry showed that β subunits had higher thermal stability than α'α subunits. The pH had a lesser effect on adhesion strength of the β subunits than on that of the α'α subunits. The adhesives made from β subunits also showed greater water resistance than those from α'α subunits and β-conglycinin. Soy protein rich in β subunits is likely a good candidate for developing water-resistant adhesives.
authors.affiliation: Bio-Material and Technology Laboratory, BIVAP, Department of Grain Science and Industry, , Kansas State University , Manhattan, Kansas 66506, United States. xss@ksu.edu
authors.forename: Xiaoqun
authors.initials: X
authors.lastname: Mo
authors.forename: Donghai
authors.initials: D
authors.lastname: Wang
authors.forename: Xiuzhi Susan
authors.initials: XS
authors.lastname: Sun
mesh_terms: D000269:Adhesives; D052179:Antigens, Plant / Q000737:chemistry* / Q000648:ultrastructure; D055598:Chemical Phenomena; D002852:Chromatography, Ion Exchange; D004355:Drug Stability; D005916:Globulins / Q000737:chemistry* / Q000648:ultrastructure; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D021122:Protein Subunits / Q000737:chemistry* / Q000302:isolation & purification; D055314:Seed Storage Proteins / Q000737:chemistry* / Q000648:ultrastructure; D012639:Seeds / Q000737:chemistry; D012995:Solubility; D030262:Soybean Proteins / Q000737:chemistry* / Q000648:ultrastructure; D013025:Glycine max / Q000737:chemistry*
chemical_list: D000269:Adhesives; D052179:Antigens, Plant; D005916:Globulins; D021122:Protein Subunits; D055314:Seed Storage Proteins; D030262:Soybean Proteins; C013894:beta-conglycinin protein, Glycine max