Researchers at the UCLA Henry Samueli School of Engineering and Applied Science, in Los Angeles have developed a way to utilise proteins, one of the most abundant biomolecules in the world, as a raw material for biorefining and biofuel production. Currently only carbohydrates and lipids are used for the production of respectively bioethanol and biodiesels.

In nutrient rich conditions, proteins are the most abundant component in fast-growing microorganisms. The accumulation rate of proteins is faster than that of any other raw material. But to effectively convert proteins to fuels and chemicals, complex cellular regulation in nitrogen metabolism has to be rewired.

Normally microorganisms use proteins from their environment to build their own proteins. To enable protein-based biorefining, the microorganisms’ protein utilization system has to be redirected to instead convert proteins to other compounds.

Proteins contain both ammonia and carbon. The research team removed the ammonia and recycled it back as a fertilizer for the algae they work with. The algae were used only as a carrier to assimilate carbon dioxide and produce protein, which results in more CO₂ fixation and growth.

Nitrogen fertilizers used in agriculture and biofuel production have become a major threat to many of the world’s ecosystems. On top of that the nitrogen-containing residuals in biofuel production can eventually turn into nitrous oxide, which is about 300 times more potent as a greenhouse gas than CO₂.

However, the production method used here not only eliminates the use of expensive photo-bioreactors for the growth of the algae, but also effectively recycles nitrogen back to the biofuel production process, thus approaching nitrogen neutrality.

© Jorn van Dooren | www.bitsofscience.org