[Show abstract][Hide abstract] ABSTRACT: The adsorption of a model protein bovine serum albumin (BSA) in expanded bed chromatography was undertaken by exploiting a
commercially available expanded bed column (20 mm i.d.) from Up Front Chromatography and Streamline DEAE (ρ=1.2 g/cm3) from Amersham Pharmacia Biotechnology. The influence of whole yeast cells on the adsorption capacity of column was explored
by employing yeast cells in a concentration ranged of 0 to 15% (w/v). Equilibrium isotherms for adsorption of BSA on Streamline
DEAE were correlated by using Langmuir equation. The presence of yeast cells resulted in decreased of BSA binding capacity
in both batch binding and expanded bed chromatography. Results indicated that the yeast cells act as competitor for proteins
to bind to the sites on adsorbents.
[Show abstract][Hide abstract] ABSTRACT: Baker’s yeast was disrupted in a 1.4-L stainless steel horizontal bead mill under a continuous recycle mode using 0.3 mm diameter
zirconia beads as abrasive. A single pass in continuous mode bead mill operation liberates half of the maximally released
protein. The maximum total protein release can only be achieved after passaging the cells 5 times through the disruption chamber.
The degree of cell disruption was increased with the increase in feeding rate, but the total protein release was highest at
the middle range of feeding rate (45 L/h). The total protein release was increased with an increase in biomass concentration
from 10 to 50% (w/v). However, higher heat dissipation as a result of high viscosity of concentrated biomass led to the denaturation
of labile protein such as glucose 6-phosphate dehydrogenase (G6PDH). As a result the highest specific activity of G6PDH was
achieved at biomass concentration of 20% (ww/v). Generally, the degree of cell disruption and total protein released were
increased with an increase in impeller tip speed, but the specific activity of G6PDH was decreased substantially at higher
impeller tip speed (14 m/s). Both the degree of cell disruption and total protein release increased, as the bead loading increased
from 75 to 85% (v/v). Hence, in order to obtain a higher yield of labile protein such as G6PDH, the yeast cell should not
be disrupted at biomass concentration and impeller tip speed higher than 20% (w/v) and 10 m/s, respectively.