Xylanase mass transfer studies in aqueous two-phase systems using spray and sieve plate columns

Factorial and Economic Evaluation of an Aqueous Two-Phase Partitioning Pilot Plant for Invertase Recovery From Spent Brewery Yeast

Aqueous two-phase systems (ATPS) have been reported as an attractive biocompatible extraction system for recovery and purification of biological products. In this work, the implementation, characterization, and optimization (operational and economic) of invertase extraction from spent brewery yeast in a semi-automatized pilot plant using ATPS is reported. Gentian violet was used as tracer for the selection of phase composition through phase entrainment minimization. Yeast suspension was chosen as a complex cell matrix model for the recovery of the industrial relevant enzyme invertase. Flow rates of phases did not have an effect, given that a bottom continuous phase is given, while load of sample and number of agitators improved the recovery of the enzyme. The best combination of factors reached a recovery of 129.35 ± 2.76% and a purification factor of 4.98 ± 1.10 in the bottom phase of a PEG-Phosphate system, also resulting in the removal of inhibitor molecules increasing invertase activity as reported by several other authors. Then, an economic analysis was performed to study the production cost of invertase analyzing only the significant parameters for production. Results indicate that the parameters being analyzed only affect the production cost per enzymatic unit, while variations in the cost per batch are not significant. Moreover, only the sample load is significant, which, combined with operational optimization results, gives the same optimal result for operation, maximizing recovery yield (15% of sample load and 1 static mixer). Overall res ults of these case studies show continuous pilot-scale ATPS as a viable and reproducible extraction/purification system for high added-value biological compounds.

Liquid-liquid extraction intensification by micro-droplet rotation in a hydrocyclone

The previous literature reports that using a hydrocyclone as an extractor intensifies the mass transfer and largely reduces the consumption of extractant from 1800-2000 kg h^-1 to 30-90 kg h^-1. However, the intensification mechanism has not been clear. This paper presents experimental and numerical methods to study the multi-scale motion of particles in hydrocyclones. In addition to the usually considered translational behavior, the high-speed rotation of dispersed micro-spheres caused by the anisotropic swirling shear flow is determined. The rotation speeds of the tested micro-spheres are above 1000 rad s^-1, which are much larger than the instantaneous rotation speed in isotropic turbulence. Due to the conical structure of a hydrocyclone, the rotation speed maintains stability along the axial direction. Numerical results show that the particle Reynolds number of micro-droplets in a hydrocyclone is equal to that in conventional extractors, but the particles have high rotation speeds of up to 10,000 rad s^-1 and long mixing lengths of more than 1000 mm. Both the rotation of micro-droplets along the spiral trajectories and the intense eddy diffusion in a hydrocyclone contribute to the extraction intensification.

A microdevice assisted approach for the preparation, characterization and selection of continuous aqueous two-phase systems: from micro to bench-scale

Aqueous two-phase systems (ATPS) have emerged as an alternative strategy for the recovery and purification of a wide variety of biological products. Typical process development requires a large screening of experimental conditions towards industrial adoption where continuous processes are preferred. In this work, it was proved that under certain flow conditions, ATPS could be formed continuously inside a microchannel, starting from stocks of phase components. Staggered herringbone chaotic micromixers included within the device sequentially and rapidly prepare two-phase systems across an entire range of useful phase compositions. Two-phase diagrams (binodal curves) were easily plotted using the cloud-point method for systems of different components and compared with previously reported curves for each system, proving that phase formation inside the device correlated with the previously reported diagrams. A proof of concept for sample partitioning in such a microdevice was performed with two different experimental models: BSA and red blood cells. Finally, the microdevice was employed to obtain information about the recovery and partition coefficient of invertase from a real complex mixture of proteins (yeast extract) to design a process for the recovery of the enzyme selecting a suitable system and composition to perform the process at bench-scale.

Enhancement of substrate concentration in microbial stereoinversion through one-pot oxidation and reduction by aqueous two-phase system

An extractive biocatalytic method of aqueous two-phase system was employed for stereoinversing (R)-1-phenyl-1,2-ethanediol into (S)-1-phenyl-1,2-ethanediol by Candida parapsilosis CCTCC M203011. It was observed that substrate and product inhibitions in microbial stereoinversion through one-pot oxidation and reduction were removed efficiently by extractive biocatalysis in aqueous two-phase system with PEG 4000/phosphate potassium system, and that the substrate concentration was enhanced from 15 to 30 g/L with product optical purity of 99.02% e.e. and yield of 90% after 60 h. Simultaneously, it was observed that change in cell morphology impedes the further enhancement of substrate concentration in this system but can be reversibly changed after stereoinversion or cultivation in systems without PEG.

Mass transfer in aqueous two-phases system packed column

The behavior of xylanase extraction in a packed column using polyethylene glycol (PEG) 4000 and dipotassium phosphate was studied. The possibility of using the packed column in continuous operations for enzyme extraction was studied since the previous work had only addressed the semi-continuous extraction of enzyme. The influence of several kinds of packings, Raschig rings, glass spheres and polystyrene rings were studied as well the superficial velocity ratio of the salt and the PEG phases. Packed column showed a good efficiency of overall mass transfer coefficient, around three times higher than sieve plate column, for xylanase extraction. The best selectivity was obtained with the polystyrene ring where 94% of xylanase was recovery to the polymeric whereas just 3% of contaminant was recovery to this phase. The residence time distribution was adjusted by the Model of Reactors in Series.