BIOPOL product

Another example where metabolic pathway engineering has made a dramatic impact is in the biodegradable polymer field. The polymer of this family most widely studied is poly-P-hydroxybutyrate (PHB) (46). Another member of the PHA family commercialized by Imperial Chemical Industries (ICI), which later became Zeneca under the trade name Biopol, is a copolymer consisting of p-hydroxybutyric acid and P-hydroxyvaleric acid. This biodegradable polymer was first used in plastic shampoo bottles by the Wella Corporation [198]. In the early part of 1996, the Biopol product line, was purchased from Zeneca by the Monsanto Company. 

The strain is able to grow on glucose and produce the copolymer PHBV to a density as high as 70-80 gP after over 70 h of growth (Byrom 1992). Shampoo bottles were produced from PHBV (trademarked as Biopol) and were available in supermarkets in Europe. However, owing to economic reasons, the Biopol products did not succeed and the PHBV patents were sold to Monsanto and further to Metabolix. 

Although first marketed by Zeneca, a company split off from ICI in 1993, under the trade name of Biopol, marketing was transferred to Monsanto in May 1996. In 1993 production capacity was 600t.p.a. but prior to the Monsanto takeover had been expected to rise to 5000-10 000 t.p.a. by the late 1990s. However, in November 1998 Monsanto announced that it was discontinuing the Biopol programme. 

It is interesting to consider that biopol)nners are by no means new to this world. It is only because of our fascination with petrochemical products that these wonderful materials have been neglected for so long. In fact, natural or biopol3Tners have been considered in the 1940s and Henry Ford has used these biopol3maers in the construction of a car. However, with the discovery of petrochemical polymers, the low cost of these quickly over shadowed natural materials. 

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. 

So far, commercial applications have been developed only for poly(3HB-co-3HV) (Biopol) by ICI [52,142]. This material has been processed into bottles for hair care products (Wella) and biodegradable motor oil [84]. Moreover, various containers, disposable razors, and food trays for holding portions of fish and meat in the refrigerated section of supermarkets were all manufactured from Biopol and sold in Japan [84,143]. In these cases, the rather expensive Biopol is used solely for its green image in order to increase product sales and to open up the market for other applications, which require biodegradability for functional reasons [18]. 

In the 1970s, ICI introduced this polymer and copolymers in which it was the major constituent as commercial products, initially under the acronym PHB, and a little later under the trade name Biopol, which referred specifically to copolymers containing p-oxybutyrate and up to 30 % of P-oxyvalerate repeating units. The copolymer is more flexible and tougher than the homopolymer [100, 101]. 

The disadvantages of all biochemical routes is the lack of variable tacticity in the polymer and, even more important, the need for time-consuming purification. PHB materials of feasible properties are only achieved with high production costs. In the 1990s, ICl sold a copolymer of 3-HB and 3-HV (BIOPOL) for about 10-20 /kg whereas the price of PP was less than 2 /kg. Therefore, a fermentative synthesis is feasible for smaller applications but not cannot compete with packaging materials such as poly(olefin)s [43 5] (Fig. 10). 

Production of polymers contributes to pollution during synthesis and after use. A polymer produced by microorganisms is already a commercial product (Biopol). Unfortunately, however, cellular synthesis remains limited by the cost of downstream processing and the fact that the synthesis is aqueous-based, and it is impossible to perform the synthesis in the absence of a solvent. Recent research describes an enzyme-catalyzed polymer synthesis in which there is no solvent. This bulk polymerization mirrors conventional synthesis but eliminates the needs for extremes of temperature and corrosive acid catalysts. This represents the first rapid and efficient synthesis of polyesters from bulk polymerization under ambient conditions with very low concentrations of a biocatalyst (Chaudhary et al., 1997). 

ICI has developed a fermentation process for PHB having various levels of polyhy-droxyvalerate (PHV) as a copolymer. This polymer is marketed under the product name BIOPOL. The material is extrudable and can be used as bottles for packaging cosmetics. Because of the high migration rate of the triacetine plasticiser used (see Chapter 4) it is not suitable for food use. Currently efforts are being made to manufacture this material as a film. 

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. 

Alicagenes eutropha produces a copolymer of hydroxyvalerate and hydroxybutyrate when deprived of key nutrients, such as amino acids and minerals. The product, biopol, represents up to 90 percent of the dry weight of the bacterium. It is comparable to polypropene in physical properties, has better flexibility at low temperatures, and is biodegradable to CO2 and water within months. However, the polymer (trade name Biopol) is not currently cost-competitive with synthetic polymers because of the high costs of the fermentation substrates and the fermentation plants. 

The readiness of the industry to use PHB in the range of low price materials has failed dimng the last years because of the costs of PHB. Production of PHB or the PHB/PHV-copolymer under the trade name Biopol for technical use was abandoned, while in the last years efforts to use PHB for the medical sphere and niche products have continued. 

Engineered PHA beads were utilized in high-affinity bio-separation [112-114], enzyme immobilization [115], protein production [116], diagnostics [117], and as an antigen delivery system [118] which is currently being commercialized [98, 69]. Poly [(R)-3-hydroxyalkanoates] (PHAs) biopolymers can be stored by bacteria, and are currently receiving much attention because of their potential as renewable and biodegradable plastics. The best known representatives are poly (hydroxybutyrate) and its copolymers with hydroxyvalerate, which have been commercialized under the trademark Biopol . 

The properties of the copolymer can be tailored to make it suitable either for molded articles such as shampoo bottles, or thin films for plastic envelopes or carrier bags. However, the polymer is costly, a container made of Biopol being about seven times more expensive than polyethylene. This polymer is now in production and used for packaging, agricultural products, and disposable items of personal hygiene. 

At present these materials are too expensive to be considered as viable alternatives to the commodity plastics in packaging but they do have potential applications in biomedical products such as orthopaedic implants and even as temporary replacements for parts of the pericardium during open-heart surgery. In this kind of application, performance is much more important than cost. However, Biopol may be able to replace non-biodegradable polymers in paper coating which would then allow paper composite materials to biodegrade much more rapidly in compost and similar environments. 

PHA is produced by different bacterial strains. One of the most studied strain is C. necator (formerly known as Wautersia eutropha, Ralstonia eutropha or Alcaligene eutrophus). It was used in industrial production by Imperial Chemical Industries (ICI PLC) to produce P(3HB-co-3HV) under the trade name of BiopoF. The Biopol patents have now been acquired by Metabolix Inc. (USA) (Verlinden et al. 2007). Until now, C. necator is still being used widely for bacterial fermentation as it is an efficient strain. Other important strains that have been studied for PHA production are Bacillus spp., Alcaligenes spp.. Pseudomonas spp., Aeromonas hydrophila, Rhodopseudomonas palustris, recombinant Escherichia coli, Burkholderia sacchari, and Halomonas boliviensis (Verlinden et al. 2007). 

Poly[3-hydroxybutyrate] was the first PHA to be produced on an industrial scale, but its brittle nature, its poor mechanical properties and its high production cost limited its application potential. In the early 1990s, Imperial Chemical Industries [ICI] started the production of poly[3-hydroxybutyrate-co-3-hydroxyvalerate] [P3HB3HV] under the trade name Biopol . This material showed lower degrees of crystallinity and superior mechanical properties. Later on, the production of Biopol was continued by Monsanto and subsequently followed up by Metabolix. PHAs were originally intended as bio-based alternatives for polyolefins used in plastic containers, films and bottles. Despite the large interest in PHAs, their application remains, however, limited due to their narrow processing window [84, 85]. 

During the process of biotechnical synthesis - usually a fermentative process - polymers primarily composed of micro-organisms are derived (one product, e.g. is Biopol). These polymers serve as energy storage for the micro-organisms. In comparison, starch fulfills the task of energy storage in plants. The most important example of fermented biopolymers to be mentioned here is polyhydroxy butyric acids and their copolyesters (one product is, e.g., Biopol). ... 

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