Production and applications of crude polyhydroxyalkanoate-containing bioplastic from the organic fraction of municipal solid waste

Abstract

A considerable economic and environmental need exists for the further development of degradable plastic polyhydroxyalkanoates (PHAs), which are produced by bacteria. However, the production cost of this bioplastic, manufactured using conventional technologies, is several times higher than that of petrochemical-based plastics. This is a major obstacle for the industrial production of PHA bioplastic for non-medical use. The aim of this review is to evaluate suitable methods for the significant reduction in bioplastic production costs. The study findings are as follows: (1) The organic fraction of municipal solid waste can be used as a raw material through acidogenic fermentation; (2) non-aseptic cultivation using mixed bacterial culture can significantly reduce the production cost; (3) biotechnology of bacterial cultivation should ensure selection of PHA-accumulating strains; (4) applications of PHAcontaining material in both construction industry and agriculture do not require expensive extraction of PHAs from bacterial biomass. The implementation of the above findings in the current manufacturing process of PHAcontaining bioplastic would significantly reduce production costs, thereby rendering PHA-containing bioplastic an economically viable and environmentally friendly alternative to petrochemical-based plastics.Keywords Bioplastic Á Polyhydroxyalkanoates Á Municipal solid waste Á Construction material Biodegradable plastics Biodegradable plasticQuantity of plastics in municipal solid waste (MSW) in USA is 27 million tons (US EPA 2011). The major portion of these materials is incinerated or landfilled, which both are not-sustainable and environmentally not-friendly solutions. A considerable economic and environmental need exists for the further development of biodegradable plastics that will be transformed to carbon dioxide and water being landfilled or disposed in the environment. Additional advantage of biodegradable plastics is that many of them are produced biologically from renewable sources so the production of these bioplastics will increase environmental and economic sustainability. However, the production cost of the bioplastics, manufactured using conventional technologies, is several times higher than that of petrochemical-based plastics. Therefore, reduction in the bioplastic production cost due to the usage of cheap raw materials and technological innovations is essential for the bioplastic production and applications. Content of accumulated PHAs can be up to 80 % of dry biomass. These substances can be extracted from bacterial biomass and used in practice as a plastic with the melting temperature 160-180°C, tensile strength 24-40 MPa, and elongation at break 3-142 %. Lastly, elasticity of the PHA plastic depends on the content of PHV in PHAs. These properties are comparable with the properties of petroleum-based thermoplastics. The most common commercial PHAs consist of a copolymer PHB and PHV together with a plasticizer/softener and inorganic additives such as titanium dioxide and calciu...

Bioplastic recovery from wastewater: A new protocol for polyhydroxyalkanoates (PHA) extraction from mixed microbial cultures

“…Polyhydroxyalkanoates are completely biodegradable and have similar properties to conventional fossil-fuel plastics, making them suitable candidates for fossil-fuel based plastics substitution. These environmentally friendly bio-based bioplastics have a great potential; the main applications range from disposable items and food packaging to chemical synthesis, agricultural, construction, pharmaceutical and biomedical uses (Reddy et al, 2003;Ivanov et al, 2014).…”

“…Industrial processes for PHA production are based on the use of pure or genetically modified cultures of selected strains and of ad hoc designed unbalanced growth media (Chen, 2010). Hence, the costs of culture maintenance, substrate formulation and both, substrate and reactor sterilization (Villano et al, 2014;Ivanov et al, 2014) turn to be key factors affecting overall PHA production cost. As alternative, the use of mixed microbial cultures (MMCs) is promising because it will help to reduce the production costs of PHAs, since MMCs do not require sterile conditions and have a wider metabolic potential than single strains.…”

Statistical physical and nutrient optimization of bioplastic polyhydroxybutyrate production by Cupriavidus necator

“…In recent years, PHAs have attracted increasing attention because they could be substitutes for conventional plastics (such as polyolefins), which can reduce petroleum consumption and alleviate environmental impact caused by plastic waste (Ivanov et al 2014). These bioplastics have application in agriculture, medicine, pharmaceutical, and packaging (Chen and Qiong 2005;Wang et al 2005).…”

Overall process of using a valerate-dominant sludge hydrolysate to produce high-quality polyhydroxyalkanoates (PHA) in a mixed culture

“…Generally, even-carbon VFAs tend to generate 3-hydroxybutyrate (3HB) monomer, whereas odd-carbon VFAs yield 3-hydroxyvalerate (3HV) and other longer-chain monomers 1 , which has been clearly evidenced by studies employing simple substrates, such as sole VFA or a VFAs mixture 8 . The monomer composition of PHA subsequently determines the thermal and mechanical properties of the polymer, including its elasticity, crystallinity and rigidness 12 . The homopolymer poly(3-hydroxybutyrate) (PHB) is a very crystalline and stiff material with a high melting point, which hinders its processing and commercial applications 13 .…”