Metabolix

This class of polymer was first launched commercially by ICI in 1990 under the trade name Biopol. Despite high hopes for mass commercial production of this material it has so far largely failed as a commercial polymer. In 1996 the business was sold to Monsanto who later sold the business to Metabolix, who also had a small business producing PHAs. 

Acknowledgement. Part of the above text was taken from the review published previously by B. Kessler and B. Witholt in Flickinger MC, Drew SW (eds) Encyclopedia of bioprocess technology fermentation, biocatalysis and bioseparation, vol 5, pp 2024-2040. We thank O. Peoples (Metabolix Inc.) for supplying information. 

It is difficult, at present, to get a clear idea of the efficiency of the various plant PHA extraction protocols. In a patent application by Metabolix [74], it was reported that the efficiency of purifying poly(3HB) which was mixed with ground rapeseed was approximately 24% when using an oil-extraction step with hexane followed by refluxing in chloroform for 22 h and evaporating the chloroform to recover poly(3HB). The co-extraction of oil with a PHA contain-... 

BAK, Bioceta, Biomax, Bionelle, Biopol, Cortec, CPLA, Easter Bio, Ecoflex, Mater-Bi, Metabolix, Nature Works PLA, Nodax, PEC (polyester carbonate), PLA, Sky Green BDP... 

Metabolix has since developed lower-cost fermentation technology for PHAs, which the company claims would permit commercial-scale production for under 2.20/kg (25). Production at this cost could open up a significant market for fermentation-based PHAs. 

A still lower-cost route to PHAs is genetic modification of plants to directly produce the final polymer. Monsanto (and others) pursued this approach and is currently being cofunded by the US Department of Energy (DOE) in a collaborative research project led by Metabolix. Switchgrass will be modified to produce PHAs, which can then be extracted from the plant material and processed to obtain a consistent composition and the desired material properties. The plant material remaining after PHA extraction can be used to produce fuels, power, or other products, creating the opportunity for a "plants as factories" biorefinery. Applications for polymers with properties similar to those of PHAs consume on the order of 13.6 million metric t annually, and it is possible that in the future PHAs will figure prominently in the plastics market. 

Metabolix,Inc. "BiotechnologyFoundation Plants,"Website http // www.metabolix. com/biotechnology%20foundation/plants.html... 

Biopol, produced by Metabolix, is a leading example of an improved poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3HB-3HV), heteropolymer. Compared to PHB, P(3HB-3HV) is less stiff, tougher, and easier to process, making it more suitable for commercial production. It is also water resistant and impermeable to oxygen, increasing its value. 

There were a number of efforts to commercialise PHA, notably by ICI in the 1980s and early 1990s, and by Monsanto in the mid 1990s. However, these attempts were largely unsuccessful due to the high cost and very limited processability and properties. In recent years, these deficiencies have been largely overcome most notably by Metabolix and by Procter Gamble s Nodax business unit, which both specialise in PHA materials development. 

PHA biodegradable polymers are still largely at the development stage of market development, although there a few commercial applications available. The main candidates for commercialisation are Biopol PHBV, being developed by Metabolix, and Nodax PHBH, marketed by Procter Gamble. 

Metabolix s PHBV (polyhydroxybutyrate valerate) was initially developed by ICI. PHBV and related copolymers are made in a pilot plant using different bacteria to create compositions with up to 70% crystallinity. Elongation can be manipulated from 5% to 100%, and melting points range between 135 and 185 °C (275-365 °F). 

The physical properties claimed for Metabolix PHA polymers are described below. 

Molecular weight - Metabolix PHA is available in molecular weights ranging from around 1,000 to over one million. 

Gas barrier properties - Metabolix PHA polymers have lower moisture vapour transmission rates than other biodegradable polymers. The oxygen transmission rates for unoriented PHA films are 25-30 cc-mil/(100 in2-day) at 77 °C, 0% relative humidity. 

Biodegradability - Metabolix PHA offer hydrolytic stability under normal service conditions but when exposed to microbial organisms naturally present they break down enzymatically in soil, composting, waste treatment processes, river water and marine environments. They also rapidly decompose to carbon dioxide and water and will degrade in anaerobic environments, unlike some other biodegradable polymers. 

UV Stability - Metabolix PHA are aliphatic polyesters and therefore have good UV stability compared with formulated polyolefins, styrenics and aromatic polyesters. 

Leading suppliers such as Metabolix and Procter Gamble have also formed collaboration agreements with strategic partners to speed up the commercialisation of PHA biodegradable polymers (Section 7.5). 

Metabolix Inc., is a private firm based in Cambridge, Massachusetts, USA, that was spun out of the Massachusetts Institute of Technology in 1992 and acquired biopolymer technology from Monsanto Inc. in 2001. Metabolix began its first commercial production of organic polyhydroxyalkanoate (PHA) resin, based on corn sugar in 2005 at an undisclosed location in the Midwest. The plant was expected to produce around 100 tonnes of material in 2005 and close to 1000 tonnes in 2006. 

The first commercial product using Metabolix PHA will be a soil stake used in farming. The item was available from early 2006. 

A pnxlrug by definition is inactive and must be converted into an active species within the biological system. There arc a variety of mechanisms by which this conversion may be accomplished. Generally, the conversion to an active form is most often carried out by mctaboli/.ing en/ymes within the body. Conversion to an aetive form may be accomplished by chemical means (c.g., hydrolysis or decarboxylation), although this is less common. Chemical transformation docs not depend on the presence or relative amounts of metabolix-... 

Glucocorticoids also have antiallergic properties, as a result of and by an inhibition of the synthesis of histamine by mast cells and basophils. Of the naturally occurring corticosteroids, only cortisol and corticosterone possess glucocorticoid activity, with cortisol the most effective. Cortisone and 11-dehydrocorticosterone lack direct glucocorticoid activity, but have potential glucocorticoid activity because they can be metabolixed to cortisol and corticosterone, respectively. 

Polyethylene glycol (PEG) and the very similar polyethylene oxide (PEO) are used as biocompatible coating agents and hydrogel forming materials, often as block or graft copolymers with other materials (Eig. IF). They are often bound to polyurethanes to form hydrophilic foams such as Biopol (Metabolix Inc.). 

At present, Metabolix Inc (Cambridge, MA) andTepha Inc (Lexington, MA) are most probably the most advanced companies in this area. Metabolix has build together with Archer Daniels Midland Company (ADM) a new plant in Clinton (Iowa) to produce about 50000 tons per year of various PHAScl for bulk applications. Tepha is focusing on the production of various sophisticated medical devices like sutures, cardiovascular tissues, meshes etc. 

The leading producer of PHAs (mostly PHBV) is Metabolix, which originated from research and development on PHAs at Massachusetts Institute of Technology. Metabolix sells PLA In sheet and Injection molding grades, as well as additives for other plastics, under the Mirel name [6]. 

Depending on the particular structure, PHAs can be nearly amorphous or can be up to about 70% crystalline, and can range from soft and elastic to stiff and brittle. Metabolix PHAs are reported to be better water vapor barriers than most biodegradable plastics. WVTRs for 50 micron PHA film at 23°C and 90% RH range from 20-150 g/m2 d. 

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