微生物聚羥基脂肪酸酯pha

1、<p>　　The Application and Industrialization of Bio-based Degradable Materials--PHA</p><p>　　Chen Guoqiang</p><p>　　(Department of Biology, Tsinghua University, Beijing)</p><p>

2、　　Introductions </p><p>　　Polyhydroxyalkanoates (PHA), using microorganisms as carbon sources and energy reserves, is generally found in the forms of inclusion bodies in microbial cells. Because of the diffe

3、rent monomer structures, there is a great variety of PHA, including not only the PHA composed of short-chain monomers and long-chain monomers, but also the copolymers formed of different monomers.</p><p>　　P

4、HA is a bio-polymer family comprising varied polyesters. As a kind of thermoplastic materials, it can be fully degraded into carbon dioxide and water in natural environment in 3-6 months without composting. More than 20

5、companies related to the mass production of PHA have been established in the world. PHA and some relevant technologies are now being formed a commercial and industrial chain covering the fields of fermentation, materials

6、, resources and medical science. The good news is that unde</p><p>　　The industrial chain of PHA in fermentation, biomedical materials, pharmaceutics, bio-fuels, fodder and plastics now is being formed. <

7、/p><p>　　PHA Applications</p><p>　　Based on the particular polymer properties, PHA with different structures and characteristics has been extensively studied and used as bio-plastics, fibres, medic

8、al implants and drug release carrier, etc. </p><p>　　At the first beginning, PHA was designed for making daily supplies and packaging materials by Wella AG Co.,Ltd from Germany. PHA is developed by P&G,

9、Biomers, Metabolix and many other companies for packing film, which is mainly used in shopping bags, coating material of containers and paper as well as disposable goods such as razors, household utensils, napkins, lady

10、cares, cups, operation clothing, carpets, composting bags, etc. Collaborating with Beijing Chemical Technology University and Shan</p><p>　　As medical material, the application of PHA has been widely researc

11、hed in sutures, restoration apparatus, bandages, blood vessel patches, bone pegs, frames, muscle tendon restoration apparatus, spinal cord bearing frame, histology restoration, nerval catheters, artificial oesophagus, wo

12、und dressings, etc. Recently research showed that PHBHHx has been successfully used in skeleton reviving because of its excellent piezoelectricity. Meanwhile, PHBHHx also has been used in the application in nerve </p&

13、gt;<p>　　Shishatskaya discovered that the cellfiber seaming of PHB and PHBV hasn’t caused any untoward effect in implantation region in one more year’s experimental stage. The researchers from Beijing also discove

14、red similar appearances in PHBHHx studies. One of PHBHHx’s most significant characteristics is that as implanted biomaterial, it is innoxious, non-immunity stimulated. The degradation outcomes of PHBHHx include monomers

15、and low polymers, they can even activate calcium ion passage and promote the</p><p>　　There’s much research on the application of PHA in the aspect of drug release. The existing release administration produc

16、ts, such as PLA, the homopolymer of lactic acid and glycolic acid, are degraded through hydrolysis. Therefore, it can’t fully realize the long-term control of drug release. At the beginning of 1990s, PHA became a candida

17、te material of drug carrier because of its biodegradability, biocompatibility and surface-erosion degradation.</p><p>　　So far, the researchers in and abroad have just researched on PHB and PHBV in drug rele

18、ase application. It is expected that the PHA of different characteristics will have more controlled property of drug release. And this is still an area to be developed.</p><p>　　Industrialization of PHA</

19、p><p>　　There is a trend to use environment-friendly non-petrochemical plastic—biodegradable plastic, green plastic or ecological plastic because of the prising rising of oil since 1980s. Lots of companies, esp

20、ecially many domestic enterprises are trying to produce various kinds of PHA experimentally or industrially. Metabolix in the U.S.A. and GreenBio in Tianjin China will respectively reach the annual production capacity of

21、 50,000 tons and 10,000 tons from 2009. There will be enough PHA material for </p><p>　　The massive supply of PHA can improve the development of itself as a kind of new stable plastic. The production costs o

22、f PHA will be continually decreasing, mainly because the synthesis of PHA is completed in aqueous phase in which PHA can be produced by the fermentation of microorganisms using any carbon resources. Unlike PLA, PBS and o

23、ther bio-plastic, the polymerization of PHA is totally a biological process. The high molecular weight, various properties and applications make PHA have a bette</p><p>　　Worldwide Enterprises Engaged in Res

24、earching and Producing PHA </p><p>　　The construction of GreenBio’s Plant</p><p>　　With the capacity of 10,000 ton/year</p><p>　　So far, numerous types of PHA, including PHB, PHBV,

25、P3HB4HB, PHBHHx and mcl PHA is ready to enter massive production.</p><p>　　The production of PHA includes strain construction, shaking flask, and pilot-scale fermentation experiment and industrialization lev

26、el fermentation. The effective microbial production of PHA depends on several factors, such as the final cell density, bacterial growth rate, the dry weight percentage of PHA in cells, the required time to the highest ce

27、ll density, conversion efficiency between substrates and products, the substrate price and the purification methods. In different development stages</p><p>　　In addition, towards the specific use, PHA should

28、 have more appropriate characteristics, including the right molecular weight, the mechanical property and thermodynamic property determined by the monomer structure, composition and PHA’s production conditions. Genetic e

29、ngineering, molecular evolution, synthesis biology and control of PHA’s production condition should be used in producing the PHA with particular structures and extra high molecular weight. </p><p>　　Market P

30、rospect of PHA</p><p>　　Owing to the various kinds and structures, PHA has the property from rigidity material to elasticity, the application of which has almost covered all the current plastic field. PHA ha

31、s incomparable advantages in environment protection, biocompatibility and drug-release property.</p><p>　　Therefore, with the continual improvements of its industrialization process and technology, the more