About this Research Topic
The plastics industry has been one of the fastest growing sectors of the world economy, because plastics are widely utilized in almost every manufacturing industry. Being synthetic polymers, the strength and shape of plastic structures can be chemically manipulated. It is estimated that nearly 150 million tons of plastics are produced every year. Currently, most petroleum-derived plastics that are widely used by humans in daily lives are non-biodegradable. However, with the increase in population and industrialization, there is now increasing awareness about the impact of these non-biodegradable plastics on the environment. Thus, a lot of efforts are now geared towards developing various biodegradable plastics. Polyhydroxyalkanoates (PHAs) are microbial polymers that are completely biodegradable, biocompatible and possess properties like various synthetic thermoplastics. PHAs are synthesized as a carbon and energy source by bacteria under conditions of limiting nutrients in the presence of excess carbon source. PHA can be converted to a wide range of finished products for application in industry, agriculture and medicine. One of the major drawbacks for commercialization is the high production cost, in which feedstock accounts for 50% of the overall price. Hence, there is a big interest in the use of cheap renewable resources.
Poly-3-hydroxybutyrate (PHB), the most widely studied member of PHA is promising as a biodegradable plastic because of its material properties which are comparable to those of the polypropylene. Furthermore, PHB has attracted much ecological interests since it can undergo rapid degradation under various environmental conditions. For instance, several reports have clearly demonstrated that PHB can be degraded under environmental conditions, such as aerobic, anaerobic and thermophilic conditions. It was also reported that rapid biodegradability of PHB would help in solving the problem of vanishing landfill space, which is one of the fastest and least expensive ways to deal with the disposal of polymers. The rate of biodegradation was found to be influenced by several factors in each environment such as microbial population, temperature, moisture level, pH and nutrient supply besides the composition, crystallinity, additives and surface area of PHA itself.
Among the hydroxy alkanoic acids, 3-hydroxybutyric acid (3-HB) is considered important and widely used in industrial and biomedical applications. Studies have shown that 3-HB exhibit anti-microbial, insecticidal, and antiviral activities, and serve as chiral building blocks for synthesis of fine chemicals including antibiotics, vitamins, and pheromones. Attempts were made to produce (R)-3-HB, however methods to prepare pure chiral 3-HB are not economically feasible. Microbial bioconversion to produce the 3-HB monomer in PHB producing bacteria with intracellular depolymerase has been used to synthesize 3-HB directly. For production of 3-HB, pathways leading to PHB production and degradation must be exploited. For instance, high yield of 3-HB can be produced in naturally PHA producing bacteria by providing the environmental condition in which cells possess high activity of intracellular depolymerase.
This Research Topic welcomes articles that specifically, addressing recent developments about problems with synthetic plastics, methods & advantages of bioplastics production, degradation methods of PHAs, and applications of 3-HB.
Keywords: Environmental pollution, global warming, bioplastics; polyhydroxyalkanoates (PHA), 3-hydroxy butyrate (3-HB)
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