ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 9, pp. 1608!1611. + Pleiades Publishing, Ltd., 2008.
Original Russian Text + P.V. Plotnikova, O.L. Vlasova, A.R. Groshikova, O.A. Pisarev, E.F. Panarin, 2008, published in Zhurnal Prikladnoi Khimii,
2008, Vol. 81, No. 9, pp. 1533!1536.
AND POLYMERIC MATERIALS
Influence of the Molecular Weight and Structural Organization
of Cationic Polyelectrolytes on Protein Flocculation
P. V. Plotnikova, O. L. Vlasova, A. R. Groshikova, O. A. Pisarev, and E. F. Panarin
St. Petersburg State Polytechnic University, St. Petersburg, Russia
Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
Received July 14, 2008
Abstract-A complex on-line procedure based on combined use of integral (spectroturbidimetry) and differ-
ential (nephelometry) light scattering methods was applied to studying the size and formation kinetics of
dispersed particles in solutions containing a protein and synthetic cationic soluble polymers. The influence
of pH of the medium and of the molecular weight and structural organization of polymers on the floccule
size and flocculation kinetics was evaluated.
Native solutions of target biologically active sub-
stances (BASs) obtained after separation of myceli-
um from the culture broth are complex systems con-
taining dissolved organic and inorganic impurities,
colloidal particles, and suspended matter. Therefore,
preparation of target products of a microbiological
synthesis involves preconcentration and purification
of native solutions. The extraction procedures used
for this purposes involve large volumes of organic
solvents (acetone, methylene chloride, butyl acetate),
which makes them environmentally hazardous and
leads to considerable loss of the target products .
Today the stability of biological liquids is con-
trolled with water-soluble polymers of various struc-
tures, whose very small additions strongly affect the
stability. Most frequently, the flocculation method
is used . The development of efficient flocculation
procedures for biotechnology requires the develop-
ment of synthetic procedures and study of properties
of newsoluble polymers, and also examination of
molecular mechanisms of their interaction with BAS.
In this study we examined how the molecular
weight and structural organization of new cationic
soluble polyelectrolytes based on poly-N,N,N,N-tri-
methylmethacryloyloxyethylammonium methyl sul-
fate (SMS) on the floccule size and flocculation
kinetics of a protein (bovine serum albumin, BSA,
MW 65000 Da, pI 4.8). BSA was used as a model of
impurity proteins present in native solutions of
target BASs. This choice is governed by the fact that
the majority of impurity proteins present in native
solutions of antitumor and antibacterial antibiotics
have molecular weights M 25000 Da and isoelectric
points pI < 5.5 .
As flocculants we used cationic water-soluble
polymers of various molecular weights and struc-
tural organizations, synthesized at the Institute of
Macromolecular Compounds, Russian Academy of
Sciences (see table). BSA was purchased from Bio-
khimreaktiv (nowBiolar, Olaine, Latvia).
Five concentrations of flocculants (0.5, 1, 2.5, 5,
) were used. The BSA concentration was
in all the experiments. Studies were per-
formed in a 0.3 M ammonium acetate solution,
which is an adequate model of the inorganic compo-
sition of native solutions of antibiotics.
After mixing solutions of the protein and polymer
and vigorous stirring, the system became more
turbid, and then the resulting insoluble complex
precipitated and the solution became colorless.
The optical density of the solutions was measured
on an SF-46 spectrophotometer. From the spectro-
turbidimetric data we calculated the wave exponent
by the formula
n = 3§logt/§logl,(1)
where n is the wave exponent; t, turbidity of the
system; and l, incident light wavelength.