In situ recovery of taxadiene using solid adsorption in cultivations with Saccharomyces cerevisiae

In this study, an engineered strain of Saccharomyces cerevisiae was used to produce taxadiene, a precursor in the biosynthetic pathway of the anticancer drug paclitaxel. Taxadiene was recovered in situ with the polymeric adsorbent Diaion © HP-20. Here we tested two bioreactor configurations and adsorbent concentrations to maximize the production and recovery of taxadiene. An external recovery configuration (ERC) was performed with the integration of an expanded bed adsorption column, whereas the internal recovery configuration (IRC) consisted in dispersed beads inside the bioreactor vessel. Taxadiene titers recovered in IRC were higher to ERC by 3.4 and 3.5 fold by using 3% and 12% (w/v) adsorbent concentration respectively. On the other hand, cell growth kinetics were faster in ERC which represents an advantage in productivity (mg of taxadiene/L*h). High resin bead concentration (12% w/v) improved the partition of taxadiene onto the beads up to 98%. This result represents an advantage over previous studies using a 3% resin concentration where the partition of taxadiene on the beads was around 50%. This work highlights the potential of in situ product recovery to improve product partition, reduce processing steps and promote cell growth. Nevertheless, a careful design of bioreactor configuration and process conditions is critical.

Treatment of nano-oil polluted wastewater in an expanded bed adsorption column based on carboxymethyl cellulose-cellulose-nickel composite beads

In the present work, spherical carboxymethyl cellulose-cellulose-nickel (CMC-C-Ni) composite beads as novel adsorbent was synthesized to make a stable expanded bed adsorption (EBA) column for the treatment of the oily wastewater collected from the downstream of rapeseed industry. The morphology and structure of the CMC-C-Ni composite beads were studied by scanning electron microscopy (SEM) and optical microscope. The SEM images revealed that the synthesized composite beads were spherical with porous structure. The pore size of the beads was in the range of 90-200 nm. The physical characteristics of the CMC-C-Ni composite beads including wet density, porosity, and water content were respectively in the ranges of 1.23-1.63 g/cm³, 82.29-90.75%, and 52-76%. The factor of bed expansion in the range of 2-3 was corresponded with Richardson-Zaki equation. The results showed that by increasing the fluid viscosity, the terminal settling velocity (U_t) was reduced. The expansion index values were between 2.77 and 3.14 that were close to 4.8 (commonly utilized index in the laminar flow regimes). CMC-C-Ni composite beads were tested when the velocity of fluid was ˂ 700 cm/h, and the D_axl was found to be ˂ 1 × 10^-5 m²/s (steady state).

Printed monolith adsorption as an alternative to expanded bed adsorption for purifying M13 bacteriophage

An ordered 3D printed chromatography stationary phase was used to purify M13 bacteriophage (M13) directly from crude cell culture. This new approach, which offers the same advantages as expanded bed adsorption (EBA) with regard to tolerating solids-laden feed streams but without the corresponding issues associated with fluidized bed stability that affect the latter, can be described as "printed monolith adsorption (PMA)". PMA columns (5, 10 and 15 cm length by 1 cm diameter) were made via a wax templating method from cross-linked cellulose hydrogel and functionalized with a quaternary amine ligand. The recovery of M13 was found to be strongly linked to load flow rate, with the highest recovery 89.7% ± 6% for 1.4 × 10¹¹ pfu/mL of resin occurring at 76 cm/h with a 10 cm column length. A recovery of 87.7% ± 5% for 1.49 × 10¹¹ pfu/mL of media was achieved with a 15 cm column length under conditions comparable to a reported EBA process. The PMA process was completed three times faster than EBA because PMA flow rates can readily be adjusted during operation, with high flow rates and low back pressure, which is unique to the ordered monolithic media geometry used. Equilibration, wash, and cleaning steps were carried out at high flow rates (611 cm/h), minimizing process time and were limited only by the volumetric flow rate capacity of the pumps used, rather than column back pressure (<0.1 MPa at 611 cm/hr). Initial capture of M13 appears to occur on the surface of the monolith solid phase (i.e. the mobile phase channel walls) and subsequently, at a slower rate, within the internal pores of the solid phase media. The difference in binding rate between these two sites is likely caused by slow pore diffusion of the large M13 particles into the pores, with similar slow diffusion out of the pores resulting in tailing of the elution peak. The results indicate that PMA is a promising technology for the efficient purification of viruses directly from crude cell culture.

Evaluation and characterization of axial distribution in expanded bed: II. Liquid mixing and local effective axial dispersion

Expanded bed adsorption (EBA) is a promising technology to capture proteins directly from unclarified feedstock. In order to better understand liquid mixing along the bed height in expanded beds, an in-bed sampling method was used to measure residence time distribution at different bed heights. A 2cm diameter nozzle column was tested with agarose raw beads (3% crosslinked agarose containing tungsten carbide). Two settled bed heights (11.5 and 23.1cm) with different expansion factors (1.4-2.6) were investigated and the number of theoretical plates (N), the height equivalent of theoretical plate (HETP) and the local effective axial dispersion coefficient (Dax) were calculated for each bed height-defined zone. The effects of expansion factor, settled bed height and mobile phase were evaluated. The results showed that N increased with the increase of expansion factors, but Dax was unaffected under fixed bed heights. Dax and HETP were found similar as a function of relative bed height for two settled bed heights tested. Higher mobile phase viscosity resulted in stronger axial dispersion. In addition, the local effective Dax under the expansion factor near 2.0 had a different profile which showed minimum values at 0.6-0.8 relative bed height, and the potential mechanism was discussed. These results would be useful for the characterization of axial dispersion and modeling protein adsorption in expanded beds under varying operation conditions.

Evaluation and characterization of axial distribution in expanded bed. I. Bead size, bead density and local bed voidage

Expanded bed adsorption (EBA) is an innovative chromatography technology that allows the adsorption of target proteins directly from unclarified feedstock, and the most important property of an expanded bed is the perfectly classified fluidization of resin beads in the column. Due to the variation of both size and density of bulk resin beads, the axial distributions of bead size, bead density and bed voidage are the inherent characteristics of an expanded bed. However, the understanding on these properties is quite limited. In this study, raw beads (3% crosslinked agarose containing tungsten carbide) and 2cm-diameter nozzle column were used as the model system and mean bead size, bead density and local bed voidage along the bed height were measured systematically with the in-bed sampling method for two settled bed heights (11.5 and 23.1cm) and different expansion factors (1.4-2.6). With the increase of bed height, mean bead size and wet density of the beads decreased from 140 to 90μm and from 4 to 2g/ml, respectively. The local bed voidage increased from 0.6 to 0.9 with the increasing bed height. The relative bed height and relative bed voidage were introduced to describe the general rule of axial distribution. Some empirical equations were used to correlate the mean bead size, bead density and local bed voidage along the bed height with the standard deviations of 10.6%, 6.1% and 5.5, respectively. In addition, a general equation was proposed to predict the axial distributions of bead size, bead density and local bed voidage in the column with standard deviations less than 10% for most of the experimental data, which would be useful for the characterization of resin beads distribution in an expanded bed under varying operation conditions.