2. Polyhydroxyalkanoate polymersDue to their previously discussed benefits, interest in biodegradable polymers produced from renewable resources has increased significantly in recent years. Polyhydroxyalkanoate polymers are naturally pro- duced by bacteria in general cultivated on agricul- tural raw materials. They can be processed to make a variety of useful products, where their biodegrad- ability and naturalness are quite beneficial in partic- ular for application in single use packaging and agriculture.Poly(3-hydroxybutyrate) (PHB), Figure 2a, is a homopolymer of 3-hydroxybutyrate and is the most widespread and best characterized member of the polyhydroxy-alkanoate family. Other members of family are displayed in Figures 2b and 2c.Poly-3-hydroxybutyrate (PHB) is a linear polyester of D (-)-3-hydroxybutyric acid which was first dis- covered in bacteria by Lemoigne in 1925. It is accu- mulated in intracellular granules by a wide variety of Gram-positive and Gram-negative organisms under conditions of a nutrient limitation other than the carbon source [10]. The molecular weight of PHB differs depending on the organism, conditions of growth and method of extraction, and can vary from about 50 000 to well over a million. The poly- mer possesses the important properties of thermo- plasticity and biodegradability in compost and dif- ferent environments comprising marine water, and, in consequence, has attracted considerable com- mercial interest.
đang được dịch, vui lòng đợi..