Production cost of PLA is low. However, its application is limited by performance mutation around 70‿such as soften, strong gas permeability, etc. These shortcomings can’t be overcome home and abroad after a number of efforts without cost increase.

      In addition, injection molding machine used to process PLA currently can’t meet demand because thermodynamic properties of PLA is quite different from that of traditional plastics. Therefore, many manufacturers are developing copolymer of D- lactic acid and L- lactic acid, aimed to control thermodynamic properties of PLA by adjusting ratio of D- lactic acid and L- lactic acid. As fermentation production process of D- lactic acid is not mature yet, future direction will focus on developing bacteria and progress of producing D- lactic acid in large scale.

      PHA has many advantages over PLA in thermodynamic properties. Though current production cost of PHA is much higher than that of PLA, PHA has many advantages in application compared with PLA, due to diversified structure and performances.

      The key technology of PHA production is acquiring microbial strains with high yield and high conversion rate; meanwhile, theses strains must be able to make use of cheap carbon source such as glucose, starch, vegetable oil, etc. Specifically speaking, it is: accumulation rate of PHA is best to be more than 80% of cell dry weigh; conversion from carbon source to PHA is best to be more than 50%; recovery rate of PHA is best to be more than 90%; cell culture density is best to be more than 150g/l; fermentation time is less than 48 hours. PHA produced in this condition is competitive.

      Sustainable development of PBS can be achieved with succinic acid as its production material produced by efficient and cheap fermentation process and strains.

       research status of application

      Biodegradable material finds application in many fields attributing to its properties of non-toxic, biodegradable, biocompatibility, etc.

      (1) application in packaging, food and beverage industry

      It is anticipated that demand of plastic packaging polymer material will reach 5 million tons in the 21st century in food packaging (restaurants, supermarket, vegetable base, etc.) and industrial products packing (household appliances, instrumentation, medical and public health, etc.). If 30% of them are difficult to ingather, the waste will reach 1.5 million tons. If biodegradable polymer material is substituted for those nom-degradable plastics, it will open up a huge market in packaging industry.

      In addition, huge market demand of disposable dishware also provides biodegradable polymer material with huge market space. For example, consumption of lunch boxes is 15 billion in 2000 in China and consumption of noodle bowls is more than 15 billion; besides, there are disposable cups, bowls, plates, etc. Particularly, after disposable dishware is forbidden to be manufactured, sold and used, biodegradable material’s market space is broadened further.

      Currently, biodegradable polymer materials used in packaging, food and beverage industry are chitin/ chitosan and its derivatives, PHB and its copolymer PHBV, etc. Products developed mainly include package, food bags, fast food dishware, cups, etc.

      (2) application in agriculture

      Biodegradable polymer material’s second largest application lies in agriculture. It can be mixed fertilizer through the process of organic degradation or mixed compost with organic waste under appropriate condition. Particularly, degradation product of biodegradable polymer material produced from chitin/ chitosan or containing chitin/ chitosan not only contributes to plant growth, but also improves soil environment.

      As a large agricultural country, annual consumption of agricultural films, mulch plastic films, cling films, rice bowl, fertilizer package and so on is a huge number. In 2000, cover area of mulch plastic films exceeds 100 million mu demanding 500000 tons of mulch plastic films, with an annual growth rate of 20-30%; annual consumption of fertilizer package totals to 230000 tons. It brings on abundant non-biodegradable waste so that making environment polluted and polymer material wasted.

      If using biodegradable polymer material instead, mulch plastic films automatically degrade to nutrients absorbable by animals and plants. In this condition, it not only relieves environmental pollution, does good to plant growth, but also achieves the purpose of recycling.

      Products developed in agriculture mainly include mulch plastic films, rice bowl, fertilizer package, compost package, etc.

      (3) application in medicine field

      An important application of biodegradable polymer material in medicine is controlled drug release. Generally speaking, polymer material serves as drug carrier in system of drug control release, which can be used in different controlled release system such as gel controlled release, microsphere and microcapsule controlled release, in-body embedded controlled release, targeted controlled release, etc. Compared with non-biodegradable drug carrier polymer, these polymers have following advantages because of its function of absorption and metaboly: slow-release rate has little dependence on drug properties; it adapts release of instable drug more; release rate is more stable, etc.

      Currently, biodegradable polymer material used as drug controlled release carrier and extensively studied includes PLA, lactic acid- caprolactone copolymer, glycollide-lactide copolymer and other aliphatic polyester, chitin/ chitosan and its derivatives.

      Another important application of biodegradable polymer material in medicine is used as bone fixtures. It includes two aspects: one is bone fixtures such as bone splint, bone screw and so on, which require implanted polymer degraded slowly in the process of healing; the other is polymer material on which cells and tissues are cultured and grown to be tissues and organs (cartilage, liver, blood vessels, skin, etc.) in some time requiring degraded slowly in quite a long time.

      For a long time, stainless steel metal polymer material is used as bone fixture polymer material home and abroad. In this case, it may bring on osteoporosis and need second surgery. If use biodegradable material instead, it can degrade automatically after completing its mission in body without second surgery.

      In addition, other applications of biodegradable polymer material in medicine include surgical suture, tissue repair, wound dressings, and so on.

      (4) application in other industries

      Besides aforesaid industries, biodegradable polymer material finds potential market in many other areas, such as one-time daily necessity, fishnet tackle, diapers, sanitary napkins, cosmetics, gloves, shoe covers, head covers, tablecloths, gardening, etc.