Hybrid nano-organisms consume CO2 and produce fuels and plastics

The bioreactor (left) after producing the first gram of biodegradable plastic using only sunlight as the energy source. [Image: Nagpal Lab / University of Colorado Boulder] 

Living factories

Researchers have developed nano-bio-hybrid organisms capable of capturing carbon dioxide (CO2) and nitrogen from atmospheric air to produce a variety of plastics and fuels.

It's still an early-stage research, but it's a promising first step for low-cost carbon sequestration and the environmentally-friendly manufacture of chemicals, the so-called green chemistry.

These true "living factories" use quantum dots, inorganic semiconductors, to energize enzymes inside bacteria.

In the initial experiments, bacterial cells produced biodegradable plastic, gasoline, ammonia and biodiesel.

"Innovation is a testament to the power of biochemical processes. We are looking for a technique that can improve CO2 capture to combat climate change and one day even replace the carbon-intensive manufacture of plastics and fuels," said Prashant Nagpal of University of Colorado, USA.

Spark plug for bacteria

The quantum dots are of the same type as those semiconductors used as pixels of some TVs. They can be passively injected into the bacteria and are designed to attach to the desired enzymes and then activate these enzymes using specific wavelengths of light.

The goal is for quantum dots to act as a spark plug for firing enzymes into microbial cells, which have the means to convert CO2 and nitrogen into other products, but do not do so naturally due to lack of photosynthesis.

It worked. Exposure to even small amounts of indirect sunlight activates the CO2 appetite of microbes without the need for any source of energy or food to perform the biochemical conversions.

"Each cell produces millions of these chemicals and we show that they can exceed their natural yields by about 200 percent," said Nagpal.

Biofactory

The bacteria, which remain in solution, release the resulting product, which then floats, and can be collected from the surface.

Different combinations of quantum dots and light produce different products: Green wavelengths cause bacteria to consume nitrogen and produce ammonia, while more red wavelengths make the microbes feast on CO2 to produce plastic.

The focus now is to confirm that everything works on a large scale and try to optimize the yield of bio-hybrid organisms.

Bibliography: Nanorg microbial factories: Light-driven renewable biochemical synthesis using quantum dot-bacteria nano-biohybrids Yuchen Ding, John R. Bertram, Carrie Eckert, Rajesh Reddy Bommareddy, Rajan Patel, Alex Conradie, Samantha Bryan, Prashant Nagpal Journal of the American Chemical Society DOI: 10.1021 / jacs.9b02549