Purification of phosphoric acid by solvent extraction

This work follows a feasibility study (187) which suggested that a process for purifying wet-process phosphoric acid by solvent extraction should be economically viable. The work was divided into two main areas, (i) chemical and physical measurements on the three-phase system, with or without impurities; (ii) process simulation and optimization. The object was to test the process technically and economically and to optimise the type of solvent. The chemical equilibria and distribution curves for the system water - phosphoric acid - solvent for the solvents n-amyl alcohol, tri-n-butyl phosphate, di-isopropyl ether and methyl isobutyl ketone have been determined. Both pure phosphoric acid and acid containing known amounts of naturally occurring impurities (Fe P0 4 , A1P0 4 , Ca3(P04)Z and Mg 3(P0 4 )Z) were examined. The hydrodynamic characteristics of the systems were also studied. The experimental results obtained for drop size distribution were compared with those obtainable from Hinze's equation (32) and it was found that they deviated by an amount related to the turbulence. A comprehensive literature survey on the purification of wet-process phosphoric acid by organic solvents has been made. The literature regarding solvent extraction fundamentals and equipment and optimization methods for the envisaged process was also reviewed. A modified form of the Kremser-Brown and Souders equation to calculate the number of contact stages was derived. The modification takes into account the special nature of phosphoric acid distribution curves in the studied systems. The process flow-sheet was developed and simulated. Powell's direct search optimization method was selected in conjunction with the linear search algorithm of Davies, Swann and Campey. The objective function was defined as the total annual manufacturing cost and the program was employed to find the optimum operating conditions for anyone of the chosen solvents. The final results demonstrated the following order of feasibility to purify wet-process acid: di-isopropyl ether, methylisobutyl ketone, n-amyl alcohol and tri-n-butyl phosphate.

Purification and crystallization of the hydroxylase component of the methanesulfonate monooxygenase from Methylosulfonomonas methylovora strain M2

The aim of the work described in this paper was two-fold: (1) the purification of the hydroxylase component of the MSAMO to electrophoretic homogeneity using a four-step chromatographic strategy and (2) the crystallization of the two-component hydroxylase of the MSAMO in order to enhance our understanding of the precise three-dimensional structure of the MSAMO, thus yielding an insight into the nature of the active site of this enzyme. Optimised crystallization conditions were identified allowing growth of crystals of the hydroxylase component of the MSAMO within five days. Crystals exhibited a brown colour suggesting the presence on an intact Rieske-iron sulfur centre and diffracted to 7.0 Å when a few degrees of data were evaluated on a beam line X11. © 2006 Elsevier Inc. All rights reserved.

LacI-mediated sequence-specific affinity purification of plasmid DNA for therapeutic applications

Affinity purification of plasmid DNA is an attractive option for the biomanufacture of therapeutic plasmids, which are strictly controlled for levels of host protein, DNA, RNA, and endotoxin. Plasmid vectors are considered to be a safer alternative than viruses for gene therapy, but milligram quantities of DNA are required per dose. Previous affinity approaches have involved triplex DNA formation and a sequence-specific zinc finger protein. We present a more generically applicable protein-based approach, which exploits the lac operator, present in a wide diversity of plasmids, as a target sequence. We used a GFP/His-tagged Lacl protein, which is precomplexed with the plasmid, and the resulting complex was immobilized on a solid support (TALON resin). Ensuing elution gives plasmid DNA, in good yield (>80% based on recovered starting material, 35-50% overall process), free from detectable RNA and protein and with minimal genomic DNA contamination. Such an affinity-based process should enhance plasmid purity and ultimately, after appropriate development, may simplify the biomanufacturing process of therapeutic plasmids.