In conditions of excess nutrients, many microorganisms usually assimilate and store those nutrients for future consumption. Polyhydroxyalkanoates (PHAs) are lipidic material accumulated by a wide variety of microorganisms in the presence of abundant carbon source. The assimilated carbon sources are biochemically processed into hydroxyalkanoate monomer units, polymerized, and then stored in the form of water insoluble inclusions (or granules) in the cell cytoplasm.
The ability to perform this polymerization process is dependent on the presence of PHA synthase. The product of this enzyme is a high molecular weight, optically active crystalline polyester. The latter is intriguingly maintained in an amorphous state in vivo. Upon isolation however, this microbial polyester is a crystalline thermoplastic with properties comparable to that of petrochemical based plastics such as polypropylene. PHAs have been the focus of attention as a potential substitute for non-biodegradable petrochemical-based plastics due to its biodegradable nature. PHAs are also biocompatible materials, thereby has potential applications in the biomedical and biopharmaceutical fields. Research is focused on the design and synthesis of various types of PHAs using locally isolated microorganisms that are capable of utilizing renewable resources such as palm oil. Novel approaches are used to identify new PHA-producing microorganisms from diverse tropical environment. Potential new isolates are subjected to genetic studies to further understand and manipulate the molecular mechanisms of PHAs biosynthesis. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) can be employed to investigate the intracellular formation and degradation processes of PHA granules.
Cyanobacteria have the potential in providing a cost effective means of producing PHAs. These are oxygen-evolving photosynthetic prokaryotes that thrive in tropical climates, some of which are known to produce PHAs. To further reduce PHAs production cost, various agricultural and domestic wastes are also being tested for their potential as suitable carbon raw materials. Given the many plantations of oil palm and rubber trees throughout the country, these plants hold tremendous potential as transgenic plants producing PHAs.
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