An overview on the production methods of polyhydroxyalkanoate natural polymers relying on productivity optimization

Today, plastics are one of the most widely used materials in human life. The physical and chemical properties of these polymers are increasingly expanding their range of applications. However, they cannot be degraded in the environment for a long time and produce toxic substances during their prolonged degradation processes. Replacing oil-based plastics by biodegradable plastics with sustainable sources could be an environmentally friendly solution. An important group of biopolymers are polyhydroxyalkanoates, which are naturally produced by some microorganisms under nutrient stress conditions and act as carbon and energy reserve. Many studies have used different methods such as genetic engineering, optimization of production conditions and utilization of inexpensive culture media such as waste waters, to produce, increase the amount, or reduce the production costs of these biopolymers by organisms. In this paper, the production of polyhydroxyalkanoates in wild and transgenic organisms and the economic aspects of replacing chemical plastics with these natural polymers are reviewed. Cost is a critical and limiting factor in the biopolymer production industry. Therefore, their production is not yet able to compete with the chemical plastics industry. Efforts by researchers and craftsmen around the world to reduce production costs continue. Undoubtedly, in the near future, due to the high pollution caused by chemical plastics and also the decline of fossil fuels consumption, the cost of producing these natural plastics will be justified.