Meet the Startup Bringing Lighting to Life

When many a Parisian tourist goes on a late-night walk through the streets of Rambouillet, a small town 44 kilometres south of Paris known for its 14th century castle, a series of cylindrical tubes lining the cobbled streets may distract them from the town’s iconic ancient landmarks with their conspicuous turquoise sheen. Juxtaposing the historical sites which define the region, these tubes, which started appearing near the end of the Covid-19 pandemic, emanate a neon-esque glow that helps animate the many streets and parks in the town. Those who had just received a Covid vaccine would be invited to immerse themselves in the light as they waited in the recovery room. In fact, these tubes were installed by the Rambouillet tourism agency, and have drawn the attention of many, from said Parisian tourists to BBC news reporters. However, what surprises them is that while these flickering lights dance soulfully in the night as if they are alive, the reason for this is because the lights are, in fact, alive. 

Glowee is a Paris-based startup which is experimenting with using bioluminescent bacteria as a means for illuminating cities. Bioluminescent organisms are those which are able to naturally emit light due to internal chemical reactions, such as fireflies. Glowee uses bioluminescent bacteria mixed with a culture solution to fill up tubes, which are then installed to act as a light source at night. In 2022, Glowee partnered with the local authority of Rambouillet to trial their bioluminescent street furniture and signage panels. The town hall pledged to turn it into ‘a full-scale bioluminescence laboratory’. Glowee also has projects elsewhere in the country, including Charles-de-Gaulle airport, and in 2017, it became the first company to develop commercial products using fluorescent bacteria. The startup aims to provide a more sustainable alternative to LEDs which does not consume as much energy from fossil fuels, therefore reducing greenhouse gas emissions.

Scientists believe that bioluminescent bacteria first came into existence 540 million years ago, during the Cambrian Explosion (a period during which many of the first complex marine organisms, including trilobites and tubeworms, started appearing and evolving rapidly to develop new senses such as vision, and eventually evolve into existing animals such as jellyfish). This led to the spectacular phenomena of glowing tidal waves and fireflies, which drew the attention of many of our ancestors. Records of such bioluminescent activity date back to thousands of years ago, and these phenomena have influenced the folklore of many regions, including Scandinavia and parts of the Indian subcontinent. While several influential thinkers, such as Aristotle, correctly suspected that bacteria were responsible, only 30 years ago did scientists discover the biochemical process behind them. Now, several organisations are taking advantage of this discovery, from medical researchers to startups such as Glowee. 

Bacteria evolved bioluminescence mainly for the purpose of self-dispersal, which helps reduce competition and increase variation. By emitting light, they draw the attention of larger organisms, such as fish, which consume the surface on which these bacteria lie. The bacteria then inhabit this organism and survive off its cellular processes, until they get egested in the organism’s faeces. The bacteria’s bioluminescence then prompts other larger organisms to consume these faeces, and the cycle continues, ensuring the survival and reproduction of the bacteria.

Conversely, other organisms use bioluminescent bacteria to deter predators either through camoflage or sudden and intense flashing. This can startle the predator or convey the existence of this predator as potential prey to larger predators, which may in turn feed on that predator. Bioluminescence also helps organisms attract mates and prey. Therefore, bioluminescent bacteria have formed symbiotic relationships with many multicellular organisms, such as the Anglerfish.

The bacteria used by Glowee are called Aliivibrio fischeri, a bioluminescent species found in marine animals such as the Hawaiian bobtail squid which gives them the ability to glow with a blue-green light. The biochemical process that produces the light involves a pair of proteins (more specifically, an aliphatic aldehyde and a reduced flavin mononucleotide) reacting together with oxygen to emit a photon of light. The reaction is fast, taking only about 20 miliseconds. It is catalysed by the enzyme luciferase (an enzyme produced specifically for bioluminescence that exists in all bioluminescent organisms) and results in the oxidation of the aldehyde to form a carboxylic acid and a non-reduced flavin mononucleotide. The equation is:

\( \text{Reduced Flavin Mononucleotide (FMNH}_2\text{)} + \text{Oxygen (O}_2\text{)} + \text{Aliphatic Aldehyde (RCHO)} \rightarrow \text{Oxidised Flavin Mononucleotide (FMN)} + \text{Fatty Acid Chain (RCOOH)} + \text{Water (H}_2\text{O)} + \text{Light} \)

Or:

\[ \text{FMNH}_2 + \text{O}_2 + \text{RCHO} \rightarrow \text{FMN} + \text{RCOOH} + \text{H}_2\text{O} + \text{Light} \]

 Aliphatic aldehydes are soluble, polar molecules containing the R-CH=O functional group (R means any stable arrangement of carbon and hydrogen atoms. It essentially means ‘rest of molecule’). They are often found in perfumes or alcoholic beverages due to their aroma. In bacteria, they can serve as a source of energy during anaerobic respiration, a deterrent to competing microorganisms or host cells defence mechanisms, or an agent in lipid decomposition, as well as a reactant for bioluminescence.

Flavin mononucleotide is a biological molecule used by bacteria mainly in respiration (specifically, it forms part of the electron transport chain, a collection of proteins bound to the inner membrane of mitochondria through which electrons pass in a series of energy-releasing reactions which eventually lead to the formation of ATP). A reduced flavin mononucleotide simply has two more electrons and protons than the non-reduced version, and the two types constantly convert to and from each other during reactions. Flavin mononucleotide is also used for DNA repair, decomposing toxic substances, and forming parts of enzymes.

To stimulate this reaction, the bacteria are first grown in a gel which provides the nutrients needed to keep the bacteria alive and allow the reaction to occur. Then, they are nurtured in saltwater aquariums before being packaged into transparent tubes for instalment.

These bacteria-powered lights have several advantages over traditional street lamps and glowsticks; firstly, they are, in theory, endlessly renewable. These bacteria can be cultivated in labs through controlled binary fission (asexual reproduction), creating a virtually infinite supply of them. Secondly, the culture is fully biodegradable, meaning it can serve as an alternative to glowsticks. Finally, the water and energy consumption is significantly lower than that required by LEDs.

While the bacteria are not harmful at all, there are still many challenges to the use of bacteria as a light source in cities. Firstly, the bacteria do not last very long – the need for a constant supply of nutrients means that once the gel runs out of nutrients, the bacteria die and stop glowing. Glowee is attempting to offset this through genetic modification to ensure the nutrients are used as efficiently as possible. For example, they developed a phenotype where bioluminescence only occurs at night, meaning reduced energy consumption during the day. Currently, they are able to last a few weeks before needing a resupply of nutrients. However, it will be difficult to maintain these cultures in the long term due to their constant need of resupplies. Another issue as that the bioluminescence is not yet bright enough to meet the target of 25 lumens per square meter for public installations (currently, the brightness reaches 15 lumens). Finally, there are concerns about whether the bacteria will be able to survive strong temperature fluctuations. Glowee has acknowledged these challenges and continues to develop their bacteria to overcome them.

Despite the skepticism, Glowee’s project managed to win the approval of the European Union as part of its Horizon 2020 program, and the European Commission has provided $1.9m of funding for it. Furthermore, France’s Institute of Health and Medical Research is providing technical support. Glowee is currently in negotiations with 40 cities across Europe and hopes the project will help promote a sense of harmony and coexistence with the environment, as well as protect the environment. With all this government support, if the trial in Rambouillet is successful and the project wins the support of the public, we may see a transformation in urban landscapes in the coming decades.