TITLE:
Preliminary study of binary protein adsorption system and potential bioseparation under homogeneous field of shear in airlift biocontactor
AUTHORS:
Yaser Dahman, Kithsiri E. Jayasuriya
KEYWORDS:
Protein Purification; Protein Adsorption; Hindrance in Adsorption; Conformation; Binary Protein Adsorption
JOURNAL NAME:
Advances in Bioscience and Biotechnology,
Vol.4 No.6,
June
24,
2013
ABSTRACT: This paper investigates the bioseparation of binary
protein mixtures using polystyrene based anion exchange resin. Adsorption
experiments were conducted in batch mode using draft-tube internally recirculate
dair lift biocontactor in comparison with the conventional shake flask batch
adsorption equilibrium experiments. Binary protein mixtures contained bovine
serum albumin (BSA) and bovine haemoglobin (BHb) at different initial fractions.
Results from single solute adsorption experiments in biocontactor showed that
both proteins were equally adsorbed onto the resin with equilibrium reached in
an equal time period. This represents similar affinities towards the negatively
charged resin surface, although BSA was expected to adsorb through specific
forces. Adsorption results showed that BSA has hindered the BHb adsorption in
the biocontactor, although adsorption of both proteins was equally hindered in
the shake flasks adsorption experiments. Moreover, adsorption of BHb was
inhibited up to 29% in the presence of BSA compared to the adsorption of BHb
from a solution containing single solute of BHb at the same initial
concentration. Similarly, the presence of BHb has hindered the adsorption of
BSA by 59%. Adsorptions of both BSA and BHb from binary solution when each
formed 75% initial fraction while the other protein formed the remaining 25%
were relatively low with equilibrium reached in shorter time. Moreover,
considerable amount of proteins remained in the solution, which demonstrates
that multilayer adsorption most likely didn’t occur at the relatively small
protein concentrations used in the present study. In general, the higher
adsorption of BHb can also be related to the compressibility of its molecules
which allowed for higher adsorption capacity. The homogeneous and lower shear
environment in the airlift biocontactor compared to the other conventional
batch adsorption in shake flask reduced the compressibility of BHb that caused
higher BSA adsorption from binary solutions of BSA and BHb, which allowed for
better bioseparation of both proteins.