Waste to bioplastics: How close are we to sustainable polyhydroxyalkanoates production? (original) (raw)
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Bacterially Produced Polyhydroxyalkanoate (PHA): Converting Renewable Resources into Bioplastics
Dependence on conventional plastics and their boundless usage have resulted in waste accumulation and greenhouse gas emissions. Recent technologies are directed towards the development of bio-green materials that exert negligible sideeffects on the environment. A biologically-synthesized plastic, polyhydroxyalkanoate (PHA), has been attracting major interests due to its similar physical properties to synthetic plastics. Unlike synthetic plastics, PHA is produced from renewable resources and is degraded aerobically by microorganisms to CO 2 and H 2 O upon disposal. The selections of suitable bacterial strains, inexpensive carbon sources, efficient fermentation and recovery processes are important aspects that should be taken into consideration for the commercialization of PHA. This chapter discusses economical strategies to reduce production costs of PHA as well as its applications in various fields.
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Accumulation of non-biodegradable plastic has shown adverse impacts on the environment and calls for a dire need for a sustainable alternative. Various microbial strains can produce bioplastics in the form of Polyhydroxyalkanoates (PHAs) as energy reserves. Many bacteria, fungi and microalgae have been studied to produce such biopolymers. PHAs are biodegradable and meet the basic requirements of life cycle environmental impact or life cycle assessments for proper disposal. They are also biocompatible and renewable. They have high Elastic modulus, Tensile modulus, melting temperature, and crystallinity with many other properties similar to synthetic plastics currently in use, making them a more reliable and sustainable substitute. Bioplastics produced from PHAs have found a myriad of applications in medicine, pharmaceuticals, agriculture and the packaging industry. This review emphasizes the structure of PHAs, their biosynthesis and relevant microbial strains employed, including gene...
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Petrochemical plastics are nonbiodegradable synthetic organic polymers. It has various applications and become an essential part of our daily lives. However, the improper disposal of plastics results in the deaths of millions of animals annually and the reduction of soil fertility and also causes severe environmental pollution. The vast consumption and accumulation of plastics have become one of the major problems throughout the world. In response to these problems, there has been considerable interest in the development and production of biodegradable microbial bioplastics which can serve as a potential alternative to petrochemical plastics. Polyhydroxyalkanoates (PHAs) are microbial bioplastics that belong to a family of biopolyesters, primarily composed of R-3-hydroxyalkanoic acid monomers unit. Wide varieties of microorganisms have been reported to synthesize polyhydroxyalkanoate (PHA) and its copolymers as intracellular inclusion under carbon-rich and other nutritional limiting conditions. PHA and its copolymers have attracted researchers and industries because of their potential use as biodegradable and biocompatible thermoplastics. It has remarkable applications in the field of tissue engineering, drug delivery, pharmaceutical, and packaging industry. The development of microbial bioplastics and their products would help to maintain the sustainability of the environment and to reduce the emission of greenhouse gases. This chapter is focused on the updated information on microbial bioplastic (PHA) production and its progress in biotechnological and other industrial applications.
The EuroBiotech Journal, 2019
The benefit of biodegradable “green plastics” over established synthetic plastics from petro-chemistry, namely their complete degradation and safe disposal, makes them attractive for use in various fields, including agriculture, food packaging, and the biomedical and pharmaceutical sector. In this context, microbial polyhydroxyalkanoates (PHA) are auspicious biodegradable plastic-like polyesters that are considered to exert less environmental burden if compared to polymers derived from fossil resources. The question of environmental and economic superiority of bio-plastics has inspired innumerable scientists during the last decades. As a matter of fact, bio-plastics like PHA have inherent economic drawbacks compared to plastics from fossil resources; they typically have higher raw material costs, and the processes are of lower productivity and are often still in the infancy of their technical development. This explains that it is no trivial task to get down the advantage of fossil-b...
Bacterial polyhydroxyalkanoates: Opportunities, challenges, and prospects
Journal of Cleaner Production, 2020
Excessive utilization of synthetic plastics has led to a major detrimental impact on the environment. Plastic pollution and accumulation in water bodies have threatened the survival of marine life. Plastic pollution can be prevented by using biopolymers that are eco-friendly and can be naturally produced by certain living organisms. The biopolymers have environmental advantages over synthetic plastics, such as biodegradability and biocompatibility. In comparison to plants and other microbial systems, bacteria can accumulate a high amount of polyhydroxyalkanoates (PHAs). However, the major stumbling block in the production of bacterial PHAs is its low cost-effectiveness due to costs associated with fermentaion and down-stream processing. In consideration with the above properties, opportunities and challeges associated with bacterial PHAs, this review focuses on structural diversity of PHAs, biosynthesis mechanism in bacteria, biodegradation, life cycle analysis, and environmental impact of bioplastic production. It further enumerates the advanced tools and techniques for bacterial PHA production, along with various factors affecting the commercialization of bioplastics. Extraction methods, down-stream processing, and biomedical applications of PHAs are also discussed. The opportunities and challenges in the commercialization of bacterial PHAs along with future scenario and environmental sustainability are presented for the purpose of fostering sustainable development.
Production of Polyhydroxyalkanoates from Renewable Sources Using Bacteria
Journal of Polymers and the Environment, 2018
Plastics play a very important role in our daily life. They are used for various purposes. But the disposal of these petrochemical-derived plastics causes a risk to the human and marine population, wildlife and environment. Also, due to the eventual depletion of petrochemical sources, there is a need for the development of alternate sources for the production of plastics. Biodegradable polymers produced by microorganisms can be used as substitutes for conventional plastics derived from petrochemical sources since they have similarity in their properties. Polyhydroxyalkanoate (PHA) is one such biopolymer that will be accumulated inside the cells of microorganisms as granules for energy storage under limiting conditions of nutrients and high concentration of carbon. Research on the microbial production of PHA should focus on the identification of costeffective substrates and also identification of a suitable strain of organism for production. The major focus of this review is the production of PHA from various cost-effective substrates using different bacterial species. The review also covers the biosynthetic pathway of PHA, extraction method, characterization technique, and applications of PHA in various sectors.
2018
Polyhydroxyalkanoates (PHA) are microbial biopolyesters utilized as “green plastics”. Their production under controlled conditions resorts to bioreactors operated in different modes. Because PHA biosynthesis constitutes a multiphase process, both feeding strategy and bioreactor operation mode need smart adaptation. Traditional PHA production setups based on batch, repeated batch, fed-batch or cyclic fed-batch processes are often limited in productivity, or display insufficient controllability of polyester composition. For highly diluted substrate streams like it is the case for (agro)industrial waste streams, fed-batch enhanced by cell recycling were recently reported as a viable tool to increase volumetric productivity. As emerging trend, continuous fermentation processes in single-, two-, and multi-stage setups are reported, which bring the kinetics of both microbial growth and PHA accumulation into agreement with process engineering, and allow tailoring PHA´s molecular structure....
2022
Diminishing sources of synthetic plastics and their unsustainable production processes have increased the demand for alternative biodegradable and sustainable polymers. Bacterial biopolymer-producing factories can carry out large-scale production of such alternatives using improved fermentation techniques, such as fed-batch and pulsed feeding of inducers, that can increase bacterial biopolymer accumulation. However, the successive downstream processing (DSP) techniques still pose challenges in making the production process both economically and environmentally sustainable. These challenges are mostly associated with biomass pre-treatment, the use of solvents, and the embedded parameters of the DSP techniques. Conventional halogenated/chlorinated solvents can be substituted with green solvents to yield PHAs of high purity (98%) for high-end applications and to establish a sustainable circular economy. As an economically and environmentally sustainable approach, the use of recycled waste as a substrate and greener extraction solvents for bacterial biopolymer production should be further explored for the efficient replacement of synthetic plastic production.