iGEM SORBONNE
NAWI
Description
Nutritive Algae for World Improvements
NAWI
Today, several global factors are compromising the sustainability of agricultural and food systems, the main one being population growth.
There are currently 7.7 billion people on Earth, and with a growth rate of 1.07% per year, we would reach 10 billion people by 2050.
An increase in population would coincide with an increase in food needs, and therefore the overexploitation of our natural resources, leading to an increase in deforestation, water consumption, and greenhouse gas emissions, of which agriculture contributes 25%.
In fact, it is crucial to develop new cultivation techniques, more efficient than the last ones, allowing us to feed the planet without destroying it.
Food production capacity is not the same around the globe, and we already dedicate 38% of the world's land to agriculture. Today's food system is a notorious contributor to environmental problems and economic inequality and is highly inefficient given the significant amount of food that is wasted. The United Nations has adopted a sustainable development goal to reduce food waste by half by 2030, both at the consumer and industry levels [1]. Nevertheless, an irreducible part of it is the non-edible parts of the food: more than 30 Mt of non-edible food waste were generated by European production in 2011 [2]. Thanks to its homogeneity, food waste could be included in an innovative approach to achieve a more sustainable agriculture.
Moreover, the intensification of agriculture damages the quality of the soil and crops. This leads to less diversified food sources and to nutritional deficiencies. We have chosen to focus on iron deficiency. Iron deficiency can result from inadequate diets, particularly in infants and young children, who need more iron as they grow. Similarly, pregnant women are at high risk of developing iron deficiency because the fetus requires large amounts of iron to develop. In developed countries, it has also been reported that people on a vegan diet are more likely to suffer from it. The main complication of iron deficiency is anemia which is an abnormal decrease in the hemoglobin level in the blood. Worldwide, 614 million women and 280 million children are anemic so it is a real challenge to ensure that iron deficiency is addressed around the world [3].
The use of new and innovative food sources is, therefore, a crucial issue to preserve food systems. These new food sources will need to meet a high nutritional standard, while reducing their impact on the environment.
Chlamydomonas reinhardtii has 12 THBs, which are homologs of truncated hemoglobins. Our research was focused on THB1, expressed in the cytosol. To improve the iron content of this microalgae, we decided to overexpress the THB1 gene. The THB1 protein is regulated by the transcription factor Nit2, which is the major transcription factor in nitrate assimilation. This hemoglobin is up-regulated by nitrate. The idea would be to use a Nit2- strain and put the THB1 transgene under a light-inducible promoter to have complete control over its expression. The growth of our algae will be done in two conditions: first, they will grow in the dark until they achieve the exponential phase and after, we will expose them to light and induce the expression of THB1. This choice of culture avoids the disruption of normal cell growth as the overexpression could cause metabolic overload.
Another part of our project will be to work with insulators. These DNA sequences allow genes to be isolated from the genomic context in eukaryotes, making them ideal for transgene expression. Insulators from a variety of eukaryote species have been tested and shown to be functional in humans or plants. Several insulator transposons have been characterized. Among these, we have decided to focus on the gypsy sequence found in the Drosophila melanogaster genome, which was shown to exhibit enhancer-blocking activity in Arabidopsis thaliana, and also to have an homolog in this plant species (Atgypsy). The gypsy insulators work with zinc finger proteins such as (Su(Hw)). With this system, we will have complete control on the expression of THB1.
Our project could benefit from taking inspiration from classic agriculture techniques like the mesoamerican’s lake-culture of Spirulina and biotechnological advances in cell culture, in order to create a large-scale and economically viable bioreactor for the production of NAWI.
Chlamydomonas can grow using both the autotrophic and heterotrophic pathways, but chlorophyll is a major contributor to bad taste. Therefore the latter, growing in the dark and using an external carbon source is preferable as it reduces chlorophyll concentration in the cells. Using food waste as the external carbon source could be the outcome of our project. Indeed, food waste represents up to a third of global food production, using it as a nutritional base for our cell culture would also assist in reducing misuse and provide an affordable solution for our growth medium.
The idea of our project came up two times. We already had a chassis as Sorbonne University teams use Chlamydomonas reinhardtii since 2018.
We brainstormed together as we wanted to find an innovative idea, proposing very complex projects like using our algae to remove the heavy metals from water or to cure some kind of diseases. And suddenly, someone said "We can eat it!”.
The first reaction was laughter but then after a little bit of research we realized all the potential behind this idea as it also reminded us of all the challenges of sustainable agriculture and soil depletion, hence the need to diversify our food sources.
Then, one day, within our team, the matter of effectiveness of food supplements was raised. In France, some packages sold in drugstores are not informative enough. Someone around us told us a story : she is vegan and wanted to buy an iron supplement at the pharmacy, but it contained lactose, which she was allergic to.
She was not aware of this information as it was lacking in the composition. After this talk, the idea of turning our alga into a food supplement came out, especially for iron deficiency. Afterwards, we did some bibliographic research and this idea became our iGEM project. We wanted to go further, and we started to think as we were going to make a start-up with a sellable product. We thought of how to make it appetizing (by changing its taste) and the different shapes it could take: candies, cake, condiments, drinks or even jelly. We have plenty of possibilities.
Microalgae are eukaryotic and unicellular organisms found in marine systems, soil environments, or freshwater. They are really important in the food chain [4]. For years and due to the agricultural challenges we face, the market for microalgae has been growing rapidly. Although they were used as food in ancient civilisations, their potential has never been fully exploited until recently.
We truly believe that microalgae have a huge potential in the innovation of future food. They are a rich source of crucial nutrients such as vitamins, proteins, fibers and minerals, have antioxidant properties, present fatty acids and natural pigments within them and hence are beneficial for human health, especially for gastrointestinal, immunological and cardiovascular health [5]. They are used in the production of superfoods and dietary supplements across the world making them a good alternative for animal husbandry. They have a short generation time and can multiply exponentially under favorable environmental conditions. As microalgae perform photosynthesis using CO2, the production of biomass can be combined with carbon fixation, therefore reducing the atmospheric CO2 concentration [4]. Finally, efficient, cost-effective and ecofriendly technologies such as bioreactors are being developed for large-scale cultivation of microalgae [5]. This avoids the use and depletion of soils. Spirulina and Chlorella are the two significant microalgae species that are widely used in the food industry. They hold the major market share in the global microalgae food markets [5].
We decided to use Chlamydomonas reinhardtii as a potential superfood.
But how could it compete with Spirulina and Chlorella in the microalgae food market?
Chlamydomonas reinhardtii is a green microalga used as a model organism associated with biotechnological applications. It is recognized as Generally Recognized As Safe for human consumption by the USA Food and Drug Administration. Moreover, a study shows that the consumption of 1 or 3g of whole-cell Chlamydomonas reinhardtii daily for 30 days had a beneficial impact on gastro-intestinal function [6]. Meaning that we can consume it and it has positive side-effects on human health. Another article points out that, because of its composition, Chlamydomonas reinhardtii has the capacity to outperform Chlorella and Spirulina as a potential superfood [7].
“C. reinhardtii outperformed them in several nutritional factors [...] regarding the lipid content and the quality of its fatty acid profile [...]. In addition, C. reinhardtii compared well with Spirulina and Chlorella in terms of its protein content and the quality of the amino acids. Even though the three species showed a high concentration of pigments (chlorophyll a and b and total carotenoids), C. reinhardtii contained significantly higher amounts of these high-value chemicals. Furthermore, C. reinhardtii contained 10 μg/g of selenium, revealing a new source of such rare and vital nutritional elements. Furthermore, C. reinhardtii contained significantly lower heavy metal load than the commercially grown Chlorella and Spirulina, which eliminates the risk of heavy metals accumulation imposed by high dosage of microalgae and seaweeds generally.”[7]
In addition, because C.reinhardtii is a model organism for the biotechnology industries, it can be easily modified to meet market needs. C.reinhardtii has a huge potential that only needs to be exploited by us. Indeed, C. reinhardtii has several advantages: haploid genome (which facilitates genetic analysis); all its three genomes have been sequenced (chloroplastic, mitochondrial, genomic); facultative phototrophic organism; fast generation rate. It is therefore possible that improvements in nutritional and/or growth qualities could one day be transposed to higher plants such as rice, wheat or corn.
However, further experiments on digestibility have to be done: “This is to complete the picture in terms of its nutrient’s bioavailability upon human and animal consumption and establish the optimal dose and way of consumption”. [7]
