The search is on to find biodegradable plastics that can be made from renewable materials at reasonable costs. Now, researchers in Germany have reported a method for rapidly producing poly-3-hydroxybutyrate (PHB) in microalgae.
PHB is renewable and biodegradable polyester with thermoplastic properties. PHB is produced naturally in bacteria such as Ralstonia eutropha and Bacillus megaterium without petroleum feedstock. And it degrades to carbon dioxide and water, unlike other plastics that may never degrade.
Researchers are exploring various ways to use algae for making more environmentally friendly and sustainable plastic, as shown in the video. Companies have produced PHB, but the bacterial fermentation methods are expensive, and plant systems grow slowly and occupy agricultural land area.
Bacteria synthesize PHB from acetyl-CoA using the enzymes ß-ketothiolase, acetoacetyl-CoA reductase, and PHB synthase. The bioplastic accumulates in the cytosol of the bacterial cells. The European researchers made PHB by introducing R. eutropha genes into a diatom called Phaeodactylum tricornutum. They confirmed with light and electron microscopy that the diatoms produced PBH in their cytosol. After only seven days, PHB comprised about 10% of the dried weight of the diatoms, according to a journal article.
The European researchers elaborated in their article on the significance of their work:
This study has demonstrated that microalgae like the diatom P. tricornutum have a great potential not only as biosynthetic factory for recombinant proteins but also as photosynthetically fueled bioreactors for synthesizing biotechnologically relevant polymers like PHB.
The researchers also noted in their article that PHB yield may be increased in the future by optimizing the enzymes or the diatoms, or using other subcellular compartments such as plastids for PHB synthesis.
Source: “Microalgae as bioreactors for bioplastic production,” Microbial Cell Factories, 10/17/11
Source: “Plastic fantastic — the future of biodegradables,” BioMed Central press release, 10/16/11
Source: “YPO Prize: Biodegradable Plastics from Algae,” YouTube
Rachel Petkewich is a freelance science writer and editor. She has worked as a research scientist in the chemical industry and spent eight years as a staff writer and editor at various science journals and magazines, including Chemical & Engineering News.