Knowledge atlas Nature

Polyhydroxybutyrate PHB (bioplastic)

Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a bio-derived and biodegradable bioplastic. It is a product of carbon assimilation in bacteria formed in limited nutrient conditions as an energy storage molecule which is metabolized when other energy sources are not available. Reference links: https://www.sciencedirect.com/science/article/abs/pii/S0045653521004744?via%3Dihub https://www.frontiersin.org/articles/10.3389/fbioe.2021.696040/full

Name of Material in the local and Latin language: Bioplastika
Type of Material: Organic
Commonly Found Locations: Laboratory environment
Major Industrial Producers or Suppliers: GreenBio Materials, Shenzhen Ecomann Technology, MHG, P&G Chemicals, Metabolix, Tian'an Biopolymer, Kaneka, Biomer, Biotrend, Bioplastech and Newlight Technologies

Colour: Gradient of light yellow
Density: 1400 kg/m³ (min 1300 – max 1500 kg/m³)
Hardness: In its 'raw' state, PHB is stiff and breakable due to the high level of crystallinity
Melting/Boiling Point: 175° C
Solubility: Water insoluble
Chemical Composition: (R)-3-hydroxybutyc acid (monomer unit): C4H8O3 PHB is poly(3-hydroxybutyrate), a homopolymer of (R)-3-hydroxybutyc acid units. These monomer molecules are produced naturally by bacteria and polymerized during the process of fermentation.

Industrial and Crafts Applications: PHB finds its applications as a biomedical, pharmacological, and veterinary material, mainly used for the production of implants, controlled encapsulation of medicines, veterinary products and fertilizers. Also, it is used in food-production industry as packaging material, but there is additionally a significant potential for using it in different sectors, for example, as a protective layer due to its water insoluble properties.
Environmental Impact: The intent behind developing a wider use of PHB is based on the notion that, on the one hand, PET plastics can be degraded in its production process, and on the other hand that the production of biopolymers creates significantly reduced carbon footprint. Bioplastics can be reused for making the same object several times, and is thus fully recyclable. However, mass application of bioplastics is still not achieved, and therefore the actual ecological impact is not determined, especially due to the dynamics and speed of the degradation of bioplastic itself, which remains underexplored.
Innovative or Emerging Applications: One possible application of bioplastics (PHAs, PHB, bacterial nanocellulose) is the production of cell phones, as a mass everyday product – from protection foils to constructive elements, making some of their components fully biodegradable and recyclable.

Extraction Methods: In the Group for Eco-Biotechnology and Drug Development, PHB (and other bioplastics) is produced through several steps: degradation – depolymerization of plastic and other materials containing PET through green processes; biofiltration – creating smaller monomer parts which are used as raw material or “food” for the microorganism. When the monomer feedstock is prepared, the microbial culture is researched, selected, and enriched so that it can process the monomer material. Depending on the used culture(s), different types of bioplastics are produced. The next step is the extraction of valuable biopolymers from the cells, and PHB of high purity is extracted, which can be done by means of different enzymes.
Processing Techniques: Depolymerization, biofiltration, fermentation, extraction, purification, moulding
Sustainability and Environmental Considerations: The tendency in the development of bioplastics is to produce fully biocompatible materials, i.e., materials that are not harmful to living tissues.
Recycling and Waste Management: New prototypes (and the new generation of bioplastic) are to be fully recyclable, making it possible for them to be reused for production of the same materials and products for a considerable, if not unlimited, number of times.

Current Research and Developments: Current developments have identified microorganisms and enzymes that can accelerate the process of composting plastic waste, and projects such as EcoPlastiC, a Horizon Europe Pathfinder project, test daring and visionary ideas for new technologies which have the potential to be commercialized and find their wide application in diverse industries.
Regulations or Restrictions: EU Bioeconomy Strategy (2018), EU Plastics Strategy (2018), EU Green Deal (2019), Single-Use Plastics Directive (2019) incl. restrictions on oxo-degradable plastics, New EU Circular Economy Action Plan (2020), EU Climate Law (2021) & EU Taxonomy (2020), Sustainable Carbon Cycles (2021), Packaging & Packaging Waste Directive (revision 2022), EU Regulation on recycled plastic materials and articles intended to come into contact with foods (2022), Substantiating Claims on environmental performance (2022), Sustainable Products Initiative (2022) / Proposal for a new Ecodesign for Sustainable Products Regulation, Policy Framework for biobased, biodegradable and compostable plastics (2022), Waste Framework Directive (revision 2023).
Relevant Organizations, Associations, Producers: (Bio)Plastic producers, Packaging industry, https://www.gopha.org/gopha