Separations Using Aqueous Phase Systems

The use of aqueous two-phase systems for the partitioning of macromolecules, organelles and cells was originally developed by Per-Ake Albertsson in Sweden in the mid-fifties [1-3]. These systems were initially applied to separations of plant organelles and viruses but their use has now extended into most areas of cell biology and biochemistry [4,5]. Since 1979 biennial International Conferences on Partitioning in Aqueous Two-Phase Systems have been held in Los Angeles (1979), Sheffield (1981), Vancouver (1983) and Lund (1985). The 5th conference was held in Oxford from 23-28 August 1987 and was entitled "Advances in Separations Using Aqueous Phase Systems in Cell Biology and Biotechnology". It is the formal presentations from this meeting which comprise this volume. In contrast to earlier books on phase partitioning [4,5] this volume contains, for the first time, worldwide contributions from over sixty partitioners from a variety of scientific disciplines, thereby providing a detailed overview of the widespread application and potential of bioseparations using phase partitioning. Disciplines include Biophysics, Biochemistry, Cell Biology, Microbiology, Biotechnology and Process Engineering, in both academic and commercial establishments. These biennial conferences allow advances in these diverse partitioning fields to be reviewed and compared; they also provide an opportunity for those considering using phase partitioning to obtain information, advice and contacts. Attendance has grown steadily over the years and 140 scientists came to Oxford. The conference consisted of ten symposia on areas of application of partitioning which have been organised as specific chapters in this volume.

A mixture of two polymers, or one polymer and a salt, in an aqueous medium separates into two phases: this phenomenon is useful in biotechn- ogy for product separations. Separation of biological molecules and particles in these aqueous two-phase systems (ATPS) was initiated over 40 years ago by P.-Å. Albertsson, and later proved to be of immense utility in biochemical and cell biological research. A boost in the application of ATPS was seen when problems of separations in biotechnology processes were encountered. Its simplicity, biocompatibility, and amenability to easy scaleup operations make the use of ATPS very attractive for large-scale bioseparations. Despite the advantages ATPS enjoys over other separation techniques, the application of two-phase systems has for a long time been confined to selected labora- ries. Recent years have, however, shown a trend in which increasing numbers of researchers employ two-phase partitioning techniques in both basic and applied research.

Rajni Hatti-Kaul and her expert coauthors combine theory, methodology, and applications in a practical collection of easily reproducible protocols for bioseparations in aqueous two-phase systems (ATPS). The protocols range from established methods to cutting-edge techniques with potential biotechnological applications. Among the methods detailed are those for ATPS preparation and characterization, for partitioning applied to soluble molecules and particulates (including whole cells, membranes, and organelles), and for the isolation and purification of proteins - including a glimpse of large-scale handling of two-phase separations. Practical and informative, with its detailed guidelines allowing researchers to adapt specific systems to their own separation needs, Aqueous Two-Phase Systems: Methods and Protocols demonstrates the scope and utility of two-phase aqueous systems in both basic and applied research.

The phase separation of incompatible liquids has been a topic of significant importance in chemical and industrial engineering for many years. Well-understood examples of this phenomenon include the phase separation of oil with water and the phase separation of non-polar organic solvents with water. Similar behavior is observed when aqueous solutions of two or more incompatible polymers or polymers and salts are mixed. In these mixtures (referred to as aqueous two-phase systems), the separated phases are composed mostly of water. Aqueous two-phase systems have been used extensively for the extraction of high-value biological products from mixtures of biological materials. In recent years, aqueous two-phase systems have also found increased use as materials for streamlining and improving the capabilities of cell and molecular assays, and for the design of advanced cell culture systems. Similar behavior of biological materials in living systems has also been observed, with emerging roles in cell physiology.

Partitioning in Aqueous Two-Phase Systems: Theory, Methods, Uses, and Applications to Biotechnology is a collection of papers that discusses the applications of aqueous two-phase systems to problems of separation and extraction of macromolecules, organelles, and cells. Papers focus on the theoretical basis and the practical details of the procedures used. Some of the papers describe in one or a few steps how two components can be separated by the investigator manipulating their partitions so that one component is in one phase and the other component is in the other phase or at the interface. Investigators can also avail of developed batch extractions for plant organelles, cell membranes, nucleic acids, and proteins. The book cites as an example the partitioning of right-side-out and inside-out vesicles (obtained from fragments of thylakoid membranes) to the top and bottom phases, respectively, of a Dx-PEG system. Other papers describe the use of the countercurrent distribution when single extraction steps are not sufficient to produce a separation in materials that do not differ greatly in their partitioning behavior. The collection can prove valuable for bio-chemists, cellular biologists, micro-biologists, and developmental biologists.

In recent years bioprocessing has increased in popularity and importance, however, bioprocessing still poses various important techno-economic and environmental challenges, such as product yields, excessive energy consumption for separations in highly watery systems, batch operation or the downstream processing bottlenecks in the production of biopharmaceutical products. Many of those challenges can be addressed by application of different process intensification technologies discussed in the present book. The first book dedicated entirely to this area, Intensification of Biobased Processesprovides a comprehensive overview of modern process intensification technologies used in bioprocessing. The book focusses on four different categories of biobased products: bio-fuels and platform chemicals; cosmeceuticals; food products; and polymers and advanced materials. It will cover various intensification aspects of the processes concerned, including (bio)reactor intensification; intensification of separation, recovery and formulation operations; and process integration. This is an invaluable source of information for researchers and industrialists working in chemical engineering, biotechnology and process engineering.

"Protein Structure Analysis - Preparation and Characterization" is a compilation of practical approaches to the structural analysis of proteins and peptides. Here, about 20 authors describe and comment on techniques for sensitive protein purification and analysis. These methods are used worldwide in biochemical and biotechnical research currently being carried out in pharmaceu tical and biomedical laboratories or protein sequencing facilities. The chapters have been written by scientists with extensive ex perience in these fields, and the practical parts are well documen ted so that the reader should be able to easily reproduce the described techniques. The methods compiled in this book were demonstrated in student courses and in the EMBO Practical Course on "Microsequence Analysis of Proteins" held in Berlin September 10-15, 1995. The topics also derived from a FEBS Workshop, held in Halkidiki, Thessaloniki, Greece, in April, 1995. Most of the authors participated in these courses as lecturers and tutors and made these courses extremely lively and successful. Since polypeptides greatly vary depending on their specific structure and function, strategies for their structural analysis must for the most part be adapted to each individual protein. Therefore, advantages and limitations of the experimen tal approaches are discussed here critically, so that the reader becomes familiar with problems that might be encountered.

Proceedings of an American Chemical Society Symposium held in San Diego, California, March 13-14, 1994