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Industrial Biopolymers Essential Fatty Acids and Prostaglandins

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Industrial Biopolymers Essential Fatty Acids and Prostaglandins 388 Nature Vol. 287 2 October /980 linear uncross-linked molecule insoluble in Industrial biopolymers hot water but soluble in organic solvents from Paul Calvert or, better, capable of melting and THE term biopolymers really includes all also be stable at the bottom of an oil well processing without decomposition. Given macromolecules of biological origin but, for several months, which, in the case of that natural structural polymers like for industrial application, biopolymers can deep North Sea wells where conditions are cellulose and collagen tend to be made be divided into two categories: those to be most severe, means it must be stable in from polar monomers and derive their used in aqueous solution and those to be saline at temperatures of about 120°C. insolubility from strong intermolecular used as solids. Polyacrylamides have been used success­ hydrogen bonding it is not surprising that The first category contains a wide range fuly in the US although the cost was high suitable examples are rare. One example is of polysaccharide thickeners, emulsifiers compared to the value of the oil produced. poly (/J-hydroxybutyrate) which is an and gelling agents used in the food industry For general use, polyacrylamides are too optically active thermoplastic polyester and in a wide range of printing and coating unstable and too easily absorbed and every with a melting point around 175°C applications. These materials can be known water soluble polymer has been produced as an intracellular storage extracted from trees, seeds and seaweeds or considered as an alternative. Xanthan gum compound by various bacteria inlcuding can be manufactured by modifying starch or a similar microbial polysaccharide seem Azotobacter vinelandii and Pseudomonas or cellulose. A variety of microorganisms to be suitable but current fermentation solanasearum. also produce water soluble extracellular methods of production make them If a suitable naturally produced thermo­ polysaccharides and it was a microbial expensive. Also, at a rate of one pound of plastic were available it may still not be product - Xanthan gum - that was the polymer used per barrel of oil produced practicable to manufacture it. Any centre of attention at a recent meeting there may not be sufficient production fermentation process leads to products in Birmingham•. Xantham gum is capacity for the polysaccharides to satisfy which must be separated and purified and produced commercially by Kelco from the potential demand even if all fermen­ this may be considerably more expensive Xanthomonas campestris and consists of a tation plants were employed for this one than a simple catalytic polymerisation, (for glucose main chain with three-unit side product. example, ethylene to polyethylene) chains (mannose-glucoronic acid­ In the light of the increasing price of oil although it may be competitive with the mannose) on every other glucose residue. It and the current interest in fermentation more expensive condensation processes was picked for its unusual gelling proper­ methods of producing industrial chemicals leading to nylons or polyethylene ties from a survey of microbial poly­ it seems natural to seek an industrial plastic terephthalate. saccharides carried out by Allene Jeanes at made by microorganisms. For a bio­ Thus while the traditional biopolymers, the US Department of Agriculture in the polymer to be used as a plastic it should be a cellulose and rubber, are still the most 1950s. It is pseudoplastic, that is it forms a important and water soluble biopolymers •A symposium on "Recent advances and Industrial are in production, a solid polymer, the gel or high viscosity solution which thins Applications in Biopolymcrs" organised by the Society of when the solution is stirred. The viscosity is Chemical Engineers was held in Birmingham in March plastic microbe, has yet to come. D stable to changes in temperature, pH and salt concentration but can be modified by adding other vegetable gums. This gives it a wide range of uses, for example in 'instant' Essential fatty acids and prostaglandins desserts and in salad dressings that flow out from Michael Crawford of the bottle but not off the salad. IN 1930 at the University of Minnesota in link between EFA and the PGs, work in One very important possible application Minneapolis, George and Mildred Burr both fields remained separate. Pharma­ for water soluble polymers is in the made the remarkable discovery that dietary ceutical companies became excited by the secondary recovery of oil. A normal oil linoleic acid was essential for growth, potential of PGs, their analogues and well only produces about 40 per cent of its development and normal function in rats. inhibitors in the fields of reproductive oil content in the combined processes of At this time, pharmacological activity of a physiology, inflammation and thrombosis. primary recovery, where the oil comes out group of uncharacterised substances from Meanwhile in the EFA camp, advances under its own pressure, and secondary semen and male accessory glands was also were made in establishing the role of EFA recovery where it is forced out by water or being studied by U.S. von Euler at the in cell membrane function, brain growth gas pumped down a series of holes Karolinska Institute in Stockholm. He and the prevention of atherosclerosis and surrounding the oil reservoir. The characterized the material as a biologically thrombosis. At the time, however, benefits extraction is limited by the failure of the active hydroxylated unsaturated fatty acid of high linoleic acid diets to the cardio­ water to displace oil from porous rock and and named it 'prostaglandin'. vascular system were largely attributed to by the tendency of the water to follow World War II interrupted research on reduction in blood cholesterol. The cracks in the rock directly to the central the 'essential fatty acids' (EFA) and important role of EFAs and PGs may well well rather than sweeping the oil before it. 'prostaglandins' (PG), and it was not until be in the integrity of vascular membranes, There are a variety of ways to enhance oil the 1950s, with the introduction of the stability of platelets and in modulation recovery (for a review see Arnold, C. W. in radioisotopes, gas-liquid chromatography of vascular tone. Microbial Polysaccharides and Polysac­ and mass spectrometry that further A recent Congress• was held to bring the cha rases ed. Berkeley, Gooday, & progress was made. During the 1950s and two fields together. Both Burr and von Ellwood, SOM/Academic Press, 1979) but 1960s EFAs were shown to be required by Euler attended the Congress as guests of a possible new approach is through a several species, including man, and linoleic honour. The sessions were designed to combination of surfactants, to allow the acid was found to be metabolized to longer highlight the precursor-product relation­ water to displace the oil from rock, with chain polyunsaturated acids. In 1964 these ship between EFAs, PGs and other water-soluble polymers to increase the were established as the precursors for the biologically important EFA metabolites. water viscosity and prevent it by-passing PGs by Van Dorp and colleagues of A number of different speakers indepen­ the oil. The requirements for such a Unilever in Holland and by Bergstrom and dently supported the idea that nutritional polymer are that it gives a high viscosity colleagues at the Karolinska Institute in management of dietary precursors should increase at low concentrations but is shear­ Sweden. affect biosynthesis of PG and other thinning for ease of pumping. It should In spite of this evidence establishing a oxygenated products. The practical applications of this include the reduction Michael Crawford is in the Nu/field Paul Calvert is in the School of Molecular Laboratories, London and was one of the •The Golden Jubilee Congress on Essential Fatty Acids and Prostaglandins was held at the University of Minnesota, May Sciences, University of Sussex. Congress program coordinators. 4-7, 1980. 0028-0836/80/400388-02$01.00 © 1980 Macmillan Journals Ltd .
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