R. Thiering et al., Carbon dioxide induced soybean protein precipitation: Protein fractionation, particle aggregation, and continuous operation, BIOTECH PR, 17(3), 2001, pp. 513-521
A novel protein fractionation technique using a volatile electrolyte has be
en developed. Carbon dioxide was used to isoelectrically precipitate 80% an
d 95% pure glycinin and beta -conglycinin fractions from soybean isolate. T
he protein fractions precipitated as primary particles 0.2-0.3 mum in diame
ter, which under optimum conditions may be recovered as aggregates up to 50
0 mum in diameter. The dependency of protein fractionation efficiency on ag
gregate settling rates has been demonstrated. The isoelectric points of the
two main soybean fractions, glycinin and beta -conglycinin, were calculate
d to be pH 5.2 and 4.95, respectively. Solution pH was accurately controlle
d by pressure in the isoelectric pH range of the different soybean protein
fractions, and a pH "overshoot" was eliminated. Volatile electrolyte techno
logy was also applied to a continuous process in order to eliminate the par
ticle recovery concerns associated with batch precipitation and to demonstr
ate the potential for scale-up. Glycinin was effectively recovered on-line
(94% glycinin recovery) with a purity approaching that of the batch process
(95%).