Photosynthesis is one of the universally known terms from biology. Almost everyone is able to say that “That is the thing plants do.”, but there is much more to photosynthesis than one might think. But why is photosynthesis so important? Well, it was behind the Great Oxygenation Event, which made the development of life as we know it possible, and to this day, it is responsible for maintaining the oxygen levels in the atmosphere. This is often attributed to plants and trees – rainforests are called “the lungs” of the planet, after all. However, more than half of the atmospheric oxygen comes from phytoplankton – microscopic algae and cyanobacteria. Additionally, they form the foundations of the food chain, which makes them crucial for the survival of our ecosystems.
For millennia, algae have been present in the human diet around the globe. Be it in the native American or the South-East Asian populations, where algae are widely popular. Our Western culture is a bit behind in the algae-eating business, but for example, sushi has already entered into our diet. Well, at least into mine. Some microalgae strains have also found their way into our diets as dietary supplements. Chlorella and Spirulina are probably the most known examples of commercially available products you can start your day with, be it as a tablet, a shot or a powder for your morning smoothie.
Algae and cyanobacteria are not only used as a food, but show tremendous potential in other industrial applications. Various pigments, such as beta-carotene or astaxanthin, can be produced by microalgae. Oleaginous strains (high content of lipids) are explored as a means to replace fossil fuels or as a source of polyunsaturated fatty acids in fish feed and dietary supplements for humans. Extensive research is also being done in the area of bioactive compounds, which can exhibit antimicrobial, antifungal or anticancer activities. Biostimulants and biofertilisers are yet another example of microalgae products possibly replacing fossil-based products currently available on the market.
During my first year of my Bachelor’s degree back at Masaryk University (CZ), I jokingly said that I would surely end up working with algae despite not being super happy with the course we had. Little did I know that this would become my reality only three years later when I joined Czech Globe – Department of Adaptive Techniques to work on my Master’s thesis. There I dived into adaptive laboratory evolution of microalgae as one of the approaches to strain improvement for lipid content. But with the international mindset I had, I knew I couldn’t spend my whole Master’s in only one lab and decided to pursue an internship at Wageningen University (NL). I dedicated one year to developing screening techniques and engineering microalgae for high lipid production in an effort to make microalgal biofuels a reality. Those three years and my three supervisors solidified my interest in algae and put me on the path I’m walking today. A holistic approach to a challenging task is my jam.
Our project – FuturoLEAF – is focusing on a different application. We aim to use microalgae as “cell factories”. What does that mean? Contrary to the biorefinery approach, in which you grow biomass and extract your target compounds, our approach relies on engineered algal cells operating as long-term catalysts producing our targeted molecules and secreting them into the growth media. We can engineer the cells to produce for example hydrogen using already present metabolic pathways or introduce new enzymes to construct a brand-new metabolic pathway producing our desired compound. However, this requires a deep understanding of metabolism and, you guessed it, photosynthesis since it is the primary source of energy in all photosynthetic organisms.
That is where our group – Photosynthetic Microbes – is the strongest. We have expertise in photosynthetic research, deciphering the various regulatory and protective mechanisms in Synechocystis sp. and Anabaena sp. and engineering production systems in thin biofilms. Every process in the cell requires energy, and in microalgae, photosynthesis supplies NADPH and ATP for the cell’s metabolism. Of course, in our ideal cell, most of the energy would go towards producing our target molecule. But that is a fight against millions of years of evolution – the cell wants to survive and reproduce, and for that, it needs a lot of energy. It is a tight balance between how much energy we can divert and when the cell will no longer survive. In our approach, biomass is an unwanted side product; therefore, we are finding solutions to prevent biomass formation while keeping the cells happy and productive.
An integral part of our project is the immobilisation – entrapment of cells into a porous matrix. This allows us to move away from suspension cultivation and decrease the energy and water demands. Not only can we lower the cost but also make the downstream processing easier. In addition, it improves the light availability for the cells, a common hindrance in suspension cultures. Unfortunately, it does not come without its own problems. The porosity of the carrier matrix is an essential characteristic as nutrients in the media need to reach the cells and photosynthetically evolved oxygen needs to be released. If this is not met, the cells won’t perform well, and we’re back to the drawing board.
I believe that the bioeconomy is the way forward. However, the long-term sustainability of the bioeconomy cannot be guaranteed only by plant biomass and by improving the way to refine conventional biomass. Instead, novel and truly sustainable platforms and advanced technologies for carbon capture are needed. This would be possible by using photosynthetic machinery and biotechnology. It’s not only us researchers, though, but we also need strong collaborations with industry and public players in order to challenge the status quo and hasten the transformation. As Sir David Attenborough said at the recent COP26 in Glasgow: “A new industrial revolution, powered by millions of sustainable innovations, is essential, and is indeed already beginning.”. I am happy to be part of this transformation through this very project and contribute to a better future.
This article was written by Michal Hubacek, PhD candidate at University of Turku