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Yutaka Tokiwa is a Senior Researcher at Okinawa Industrial Technology Center, who has published extensively on the biodegradability of plastics. [1] [2] [3] He has an h-index of 61 according to Google Scholar. [4]
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Yutaka Tokiwa is a Senior Researcher at Okinawa Industrial Technology Center, who has published extensively on the biodegradability of plastics. [1] [2] [3] He has an h-index of 61 according to Google Scholar. [4]
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradation occurs under a specific set of circumstances.
Polymer degradation is the reduction in the physical properties of a polymer, such as strength, caused by changes in its chemical composition. Polymers and particularly plastics are subject to degradation at all stages of their product life cycle, including during their initial processing, use, disposal into the environment and recycling. The rate of this degradation varies significantly; biodegradation can take decades, whereas some industrial processes can completely decompose a polymer in hours.
Plastic mulch is a product used in plasticulture in a similar fashion to mulch, to suppress weeds and conserve water in crop production and landscaping. Certain plastic mulches also act as a barrier to keep methyl bromide, both a powerful fumigant and ozone depleter, in the soil. Crops grow through slits or holes in thin plastic sheeting. Plastic mulch is often used in conjunction with drip irrigation. Some research has been done using different colors of mulch to affect crop growth. Use of plastic mulch is predominant in large-scale vegetable growing, with millions of acres cultivated under plastic mulch worldwide each year.
Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class that are of interest as bio-derived and biodegradable plastics. The poly-3-hydroxybutyrate (P3HB) form of PHB is probably the most common type of polyhydroxyalkanoate, but other polymers of this class are produced by a variety of organisms: these include poly-4-hydroxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO) and their copolymers.
Polyvinyl alcohol (PVOH, PVA, or PVAl) is a water-soluble synthetic polymer. It has the idealized formula [CH2CH(OH)]n. It is used in papermaking, textile warp sizing, as a thickener and emulsion stabilizer in polyvinyl acetate (PVAc) adhesive formulations, in a variety of coatings, and 3D printing. It is colourless (white) and odorless. It is commonly supplied as beads or as solutions in water. Without an externally added crosslinking agent, PVA solution can be gelled through repeated freezing-thawing, yielding highly strong, ultrapure, biocompatible hydrogels which have been used for a variety of applications such as vascular stents, cartilages, contact lenses, etc.
Polycaprolactone (PCL) is a synthetic, semi-crystalline, biodegradable polyester with a melting point of about 60 °C and a glass transition temperature of about −60 °C. The most common use of polycaprolactone is in the production of speciality polyurethanes. Polycaprolactones impart good resistance to water, oil, solvent and chlorine to the polyurethane produced.
Nylon 6 or polycaprolactam is a polymer, in particular semicrystalline polyamide. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization; this makes it a special case in the comparison between condensation and addition polymers. Its competition with nylon 6,6 and the example it set have also shaped the economics of the synthetic fibre industry. It is sold under numerous trade names including Perlon (Germany), Dederon, Nylatron, Capron, Ultramid, Akulon, Kapron, Rugopa (Turkey) and Durethan.
Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a thermoplastic polyester with backbone formula (C
3H
4O
2)
n or [–C(CH
3)HC(=O)O–]
n, formally obtained by condensation of lactic acid C(CH
3)(OH)HCOOH with loss of water. It can also be prepared by ring-opening polymerization of lactide [–C(CH
3)HC(=O)O–]
2, the cyclic dimer of the basic repeating unit.
Bioplastics are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch and rice starch, straw, woodchips, sawdust, recycled food waste, etc. Some bioplastics are obtained by processing directly from natural biopolymers including polysaccharides and proteins, while others are chemically synthesized from sugar derivatives and lipids from either plants or animals, or biologically generated by fermentation of sugars or lipids. In contrast, common plastics, such as fossil-fuel plastics are derived from petroleum or natural gas.
Biodegradable plastics are plastics that can be decomposed by the action of living organisms, usually microbes, into water, carbon dioxide, and biomass. Biodegradable plastics are commonly produced with renewable raw materials, micro-organisms, petrochemicals, or combinations of all three.
Fibroin is an insoluble protein present in silk produced by numerous insects, such as the larvae of Bombyx mori, and other moth genera such as Antheraea, Cricula, Samia and Gonometa. Silk in its raw state consists of two main proteins, sericin and fibroin, with a glue-like layer of sericin coating two singular filaments of fibroin called brins. Silk fibroin is considered a β-keratin related to proteins that form hair, skin, nails and connective tissues.
Poly(3-hydroxybutyrate) depolymerase (EC 3.1.1.75, PHB depolymerase, systematic name poly[(R)-3-hydroxybutanoate] hydrolase) is an enzyme used in the degradation processes of a natural polyester poly(3-hydroxyburate). This enzyme has growing commercialization interests due to it implications in biodegradable plastic decomposition.
Oxo-degradation, refers to the process by which plastics that contain additives that accelerate its breakdown into smaller fragments, called microplastics, when exposed to heat, light or oxygen. This is in contrast to biodegradable or compostable plastics, which break down at the molecular or polymer level. Oxo-degradable plastics are currently banned in the EU, but still permitted in other jurisdictions such as the UK.
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be molded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to their widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.
Biodegradable additives are additives that enhance the biodegradation of polymers by allowing microorganisms to utilize the carbon within the polymer chain as a source of energy. Biodegradable additives attract microorganisms to the polymer through quorum sensing after biofilm creation on the plastic product. Additives are generally in masterbatch formation that use carrier resins such as polyethylene (PE), polypropylene (PP), polystyrene (PS) or polyethylene terephthalate (PET).
Polybutylene succinate (PBS) is a thermoplastic polymer resin of the polyester family. PBS is a biodegradable aliphatic polyester with properties that are comparable to polypropylene.
Poly(ethylene succinate) (PES) is an aliphatic synthetic polyester with a melting point from 103–106 °C. It is synthesized from dicarboxylic acids; either by ring-opening polymerization of succinic anhydride with ethylene oxide or by polycondensation of succinic acid and ethylene glycol. Thermophilic Bacillus sp. TT96 is found in soil and can degrade PES. Mesophilic PES degrading microorganisms were found in the Bacillus and Paenibacillus species; strain KT102; a relative of Bacillus pumilus was the most capable of degrading PES film. The fungal species NKCM1003 a type of Aspergillus clavatus also degrades PES film. The solubility of lithium salts (e.g. lithium perchlorate, LiClO4) in PES made it a good alternative to poly(ethylene oxide) (PEO) during early development of solid polymer electrolytes for lithium ion batteries.
Poly(hexamethylene carbonate) (PHC) is an organic polymer. It can be biodegredated to form adipic acid and di(6-hydroxyhexyl) carbonate by Roseateles depolymerans 61A. PHC can be synthesized to terminate in primarily hydroxyl groups or methyl carbonate groups depending on the concentrations of monomers during synthesis. PHC with the hydroxyl end groups has less thermal stability than PHC with methyl carbonate end groups. The hydroxyl group allow for an unzipping reaction to take place in which the polymer chain bends back on itself and the hydroxyl group reacts with an acetyl mid chain, resulting in a shorter chain and a looped molecule. This type of degradation quickly shorten the length of the PHC.
Synthetic microbial consortia or Synthetic microbial communities are multi-population systems that can contain a diverse range of microbial species, and are adjustable to serve a variety of industrial, ecological, and tautological interests. For synthetic biology, consortia take the ability to engineer novel cell behaviors to a population level.
Plastic degradation in marine bacteria describes when certain pelagic bacteria break down polymers and use them as a primary source of carbon for energy. Polymers such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) are incredibly useful for their durability and relatively low cost of production, however it is their persistence and difficulty to be properly disposed of that is leading to pollution of the environment and disruption of natural processes. It is estimated that each year there are 9-14 million metric tons of plastic that are entering the ocean due to inefficient solutions for their disposal. The biochemical pathways that allow for certain microbes to break down these polymers into less harmful byproducts has been a topic of study to develop a suitable anti-pollutant.
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