Using Microbial metabolism to produce bioplastics and biopolymers

what are biopolymers?

Natural polymers produced by living organisms, such as polysaccharides and proteins, which can be used to create biodegradable plastics and materials.

*Biobased doesn’t equate to biodegradability

how are biodegradable polymers degraded?

By microbes and their enzymes that break down the polymer chains into smaller molecules.

what are some examples of biobased materials produced by terrestrial plants & their associated uses?

• Natural fibres for construction

• Cellulose for adhesives

• Hemicellulose for paper

• Lignin for fibres

• Starch for biodegradable plastic bags

what are the 3 main biobased polymers?

• Cellulose (from plants and microbes)

• Polyhydroxyalkanoates (PHA) (from microbes)

• Lignin (from plants)

what can the metabolic intermediates lactic acid and succinic acid be exploited for?

They can be used to produce biodegradable plastics, solvents, and various chemicals.

what are some biobased starting materials?

• Cellulose derived sugars (glucose, arabinose, xylose…)

• Starch derived glucose and maltose

• Waste - food waste, food processing side streams, agricultural waste

what are the 3 fermentation products generated by microbial metabolism and what are their associated plastics?

1. Lactic acid → Lactide → Polylactate

2. Ethanol → Ethylene → Polyethylene

3. Isobutanol → Isobutylene → Polyisobutene

what is succinate used to make?

Polybutylene succinate (PBS), a biodegradable polymer used in packaging and other applications.

how are PHAs (polyhydroxyalkanoates) produced by fatty acid oxidation by microbes?

Fatty acid oxidation into acyl-CoA → 3-hydroxyacyl-CoA → PHA - polyhydroxyalkanoate

what are some examples of starting materials used to make biopolymers?

Corn, corn stalks, grass/ wood can be converted into PLAs or PHAs

what are examples of bacteria that produce cellulose?

• Acetobacter xylinum, Gluconacetobacter, and Agrobacterium, Aerobacter, Salmonella.

• These bacteria synthesise cellulose as an extracellular polysaccharide.

what makes bacterial cellulose different to plant cellulose?

• Microfibrils (strong threads made of long cellulose chains running parallel to one another, joined together by H bonds forming strong cross linkages) are 100x thinner than plant cellulose fibres

• High tensile strength and greater water retention capacity.

• Bacterial cellulose is also biodegradable and can be produced in a pure form, making it useful for various applications like wound dressings and food products.

what is the pathway for bacterial cellulose synthesis?

• Conversion of glucose to glucose-6-phosphate (hexokinase)

  

• G6P into G1P using PGM (phosphoglucomutase)

• G1P into UDPGlc (uridine diphosphate glucose)

• UDPGlc into cellulose

which bacterial biopolymers take the longest to compost?

Biopolyesters such as polyhydroxyalkanoates (PHAs) or microbial polyesters. These typically require specialized conditions for biodegradation.