Biopol is made in industrial fermentor by bacteria that converts sugars (refined from corn or beet) into polymer. But US scientists recently announced an important step towards making biodegradable plastic directly in plants. Genetically engineered Arabidopsis thaliana a type of cress was used for the purpose. Costs can be reduced tenfold if the plastics are produced by plants. With transgenic plants producing PHA pr ice comes to US 20 cents per kg. which is close to that of starch. Potatoes can be genetically engineered to make and store plastics instead of starch in their tubers. The idea of producing PHAs in transgenic plants was first described by MIT researchers in a 1989 patent application. By the mid-1990s several research groups had successfully produced PHB in various plants, ranging from Arabidopsis thaliana, an experimental research plant to commercial oilseed crops and even cotton. Full scale commercial dev e lopment of transgenic PHA crops is still 5-7 years away. The cost of plant-derived PHAs will depend upon several factors, such as plant crop used, content of PHAs, price of crop, location, scale, ease of extraction. If yields of PHAs are 20-50% of the crop then price of PHAs can be competitive with synthetic plastics. 1 m hectares ( 10 X 10m2) of farmland would produce 375000t of plastic. This quantity of plastic is only 5% of the US demand of plastic packaging market. Metabolic engineering efforts are on for Arabidopsis, Canola, Brassica, soybeans, corn and potato.
Chris Somerville of the US Department of Energy's plant research laboratory at Michigan state University led a team collaborating with the James Madison University in Virginia to modify the cress. The investigators inserted two foreign genes into cress, taken from bacteria Alcaligenes eutrophus which makes PHB naturally. Agrobacterium tumefaciens is used as Trojan horse bacterium to transfer two genes to cress plant Arabidopsis thaliana. Plants produced 20-100 mcg / gram of plant tissue , PHB. Production should be raised 100 fold to com mercialize it. One potential problem is plants become sick. This is perhaps because new genes divert carbon away from the essential metabolites to PHB production. But if these genes are introduced in beet, potato plants which have too much excess of energy-storing carbon such as starch, such diversion of carbon to PHB is not damaging. However, USA only can think of PHB instead of starchy food. Genetically-engineered Arabidopsisplants so far have produced small amounts of pure PHB. But it is expected that co-polymers of PHB-HV can be made directly in crops.
Oilseed crops are most amenable targets for seed-specific PHA production. Since both oil and PHA are derived from acetyl-CoA, it is diversion of acetyl CoA to PHB accumulation. Plastids of plants are targeted for PHB synthesis by engineered genes. Arabidopsis thaliana is closely related to oil producing crop rapeseed which in fact is a target crop for PHB production on agricultural scale. Rapeseed, Sunflower and soyabean are the crops which can be genetically transformed to produce PHA. ZENECA Seeds and Monsanto are working on it. Monsanto will commercialise it by 2003 AD. Monsanto is trying to improve the performance of this bioplastic. The bioplastic will be initially used to produce paper coating and a film for food packaging.
Although PHB can be made by plants with little genetic work, for making PHBV four genes of bacterial origin were needed to be engineered into the rapeseed plant to make them produce PHBV by modification of two separate metabolic pathways. This was because, plants do not produce valeric acid which is required to produce PHBV. Gruys and his team from Monsanto, in St. Louis, Missouri have done this state-of-the-art work. Three genes are used from Ralstonia eutropha (formerly named as Alcaligenes eutrophus) and accomplish three final steps in the polymer pathway. Fourth gene for making valeric acid comes from E.coli.
The Monsanto team estimate that polymer concentration need to be around 15% dry weight to make extraction and processing economic. While today it is just 3%. Thus lot of research is needed before final commercialisation.
In a surprise move Monsanto also declared to its shareholders that it had no plans to produce bioplastics in genetically engineered plants though there were impressive successes. They are ready to give their technology to others on license.
The Forest Genetics Research Institute (Suwon, Korea), a subsidiary of the South Korean Ministry of Agriculture and Forestry, has developed a process to produce PHB in the chloroplasts of genetically engineered aspen trees (poplars). Two genes from Alcaligenes eutrophus have been transferred to poplar plant cells. PHB present in chloroplasts can be obtained from leaves. Leaves are dried, crushed to fine powder and then bioplastic is extracted with chloroform.
The Massachusetts Institute of Technology (MIT) has been awarded two patents in USA covering the production of biodegradable plastics in plants. These are seventh and eighth in a series exclusively to Metabolix (Cambridge, Mass). Metabolix is developing a range of technologies for PHA production including enzyme catalysed polymerisation and fermentation routes.
It has also been shown by Metabolix Inc. that transfer of the proprietary PHA genes into plants results in accumulation of PHA polymers in the new host. Current research aims to optimize expression of these genes and target polymer synthesis to easily processable tissues like the seeds or tubers. Polymer extracted from these sources is expected to compete directly on a price-performance basis with current nonrenewable pl astics. Full scale plant crop production is expected in four to ten years.
The polymers produced in plants are structurally identical to those from bacteria, so that processors can develop applications using fermented material in expectation of using plant- derived PHAs in the future. PHAs are also a useful industrial source of chiral building blocks for the chemical industry. Stereochemically pure monomers (R -3-hydroxyacids and their derivatives) are readily available by depolymerization of the PHA polymer s. Monomer derivatives have been supplied to customers by Metabolix under research agreements.
Chris Somerville of the US Department of Energy's plant research laboratory at Michigan state University led a team collaborating with the James Madison University in Virginia to modify the cress. The investigators inserted two foreign genes into cress, taken from bacteria Alcaligenes eutrophus which makes PHB naturally. Agrobacterium tumefaciens is used as Trojan horse bacterium to transfer two genes to cress plant Arabidopsis thaliana. Plants produced 20-100 mcg / gram of plant tissue , PHB. Production should be raised 100 fold to com mercialize it. One potential problem is plants become sick. This is perhaps because new genes divert carbon away from the essential metabolites to PHB production. But if these genes are introduced in beet, potato plants which have too much excess of energy-storing carbon such as starch, such diversion of carbon to PHB is not damaging. However, USA only can think of PHB instead of starchy food. Genetically-engineered Arabidopsisplants so far have produced small amounts of pure PHB. But it is expected that co-polymers of PHB-HV can be made directly in crops.
Oilseed crops are most amenable targets for seed-specific PHA production. Since both oil and PHA are derived from acetyl-CoA, it is diversion of acetyl CoA to PHB accumulation. Plastids of plants are targeted for PHB synthesis by engineered genes. Arabidopsis thaliana is closely related to oil producing crop rapeseed which in fact is a target crop for PHB production on agricultural scale. Rapeseed, Sunflower and soyabean are the crops which can be genetically transformed to produce PHA. ZENECA Seeds and Monsanto are working on it. Monsanto will commercialise it by 2003 AD. Monsanto is trying to improve the performance of this bioplastic. The bioplastic will be initially used to produce paper coating and a film for food packaging.
Although PHB can be made by plants with little genetic work, for making PHBV four genes of bacterial origin were needed to be engineered into the rapeseed plant to make them produce PHBV by modification of two separate metabolic pathways. This was because, plants do not produce valeric acid which is required to produce PHBV. Gruys and his team from Monsanto, in St. Louis, Missouri have done this state-of-the-art work. Three genes are used from Ralstonia eutropha (formerly named as Alcaligenes eutrophus) and accomplish three final steps in the polymer pathway. Fourth gene for making valeric acid comes from E.coli.
The Monsanto team estimate that polymer concentration need to be around 15% dry weight to make extraction and processing economic. While today it is just 3%. Thus lot of research is needed before final commercialisation.
In a surprise move Monsanto also declared to its shareholders that it had no plans to produce bioplastics in genetically engineered plants though there were impressive successes. They are ready to give their technology to others on license.
The Forest Genetics Research Institute (Suwon, Korea), a subsidiary of the South Korean Ministry of Agriculture and Forestry, has developed a process to produce PHB in the chloroplasts of genetically engineered aspen trees (poplars). Two genes from Alcaligenes eutrophus have been transferred to poplar plant cells. PHB present in chloroplasts can be obtained from leaves. Leaves are dried, crushed to fine powder and then bioplastic is extracted with chloroform.
The Massachusetts Institute of Technology (MIT) has been awarded two patents in USA covering the production of biodegradable plastics in plants. These are seventh and eighth in a series exclusively to Metabolix (Cambridge, Mass). Metabolix is developing a range of technologies for PHA production including enzyme catalysed polymerisation and fermentation routes.
It has also been shown by Metabolix Inc. that transfer of the proprietary PHA genes into plants results in accumulation of PHA polymers in the new host. Current research aims to optimize expression of these genes and target polymer synthesis to easily processable tissues like the seeds or tubers. Polymer extracted from these sources is expected to compete directly on a price-performance basis with current nonrenewable pl astics. Full scale plant crop production is expected in four to ten years.
The polymers produced in plants are structurally identical to those from bacteria, so that processors can develop applications using fermented material in expectation of using plant- derived PHAs in the future. PHAs are also a useful industrial source of chiral building blocks for the chemical industry. Stereochemically pure monomers (R -3-hydroxyacids and their derivatives) are readily available by depolymerization of the PHA polymer s. Monomer derivatives have been supplied to customers by Metabolix under research agreements.
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