Researchers at Tel Aviv University have found a way to increase the yield of hydrogen from unicellular algae 5 times for the vehicles of the future

The significance of the discovery: the potential of microalgae as a future source of energy is much greater than scientists thought until today

Researchers at Tel Aviv University discovered that single-celled algae emit hydrogen throughout the hours of daylight, and found an effective way to increase the output 5 times through genetic engineering. In doing so, they disproved a long-standing assumption - that these microalgae only emit hydrogen for a few minutes a day, at sunrise, and therefore only a tiny amount of hydrogen can be extracted from them. The discovery means that the potential of microalgae as a future energy source is much greater than scientists have thought until now. More than that: it is possible that in the future we will be able to grow microalgae by agricultural means, and extract from them all the energy we need. The research was published this month in the journals: Plant Physiology and Biotechnology for Biofuels.

The research was led by Dr. Yeftah Yacovi, head of the Renewable Energy Laboratory at the School of Plant Sciences and Food Security, in the Faculty of Life Sciences of Tel Aviv University. It was supported by the Prime Minister's Directorate for Petroleum Substitutes headed by Eyal Rosner, and was attended by a number of researchers from Dr. Yacovi's laboratory: PhD student Rinat Smiatitz, Dr. Oded Liran, Dr. Habiva Eilenberg and research student Ido Viner.

The hydrogen motor revolution
"Hydrogen is an energy source with tremendous advantages," says Dr. Yacovi. "First, its energy content is enormous: the driving range of a hydrogen-powered car is more than 500 km for 5 kg of hydrogen, and a bicycle will go over 100 km on only 30 grams of hydrogen; Secondly, hydrogen is not a pollutant at all: the process of utilizing it in the electric fuel cells only creates water vapor, and from the exhaust of a car powered by hydrogen only clean water will be emitted, even suitable for drinking!" And it's not just about dreams for the future: the hydrogen motor revolution is happening here and now. Already in 2015, the companies Toyota and Hyundai began serial production of 'Mirai' ('future' in Japanese) and 'Tucson' cars - electric vehicles powered by hydrogen gas; At the same time, electric bicycles are also converted to hydrogen; Hydrogen fueling stations are currently being built in Japan, Scandinavia, Germany and California; And scientists all over the world are looking for efficient and accessible methods to produce hydrogen on a large scale.

According to Dr. Yacovi, already in 1942, scientists discovered that microalgae - single-celled algae that are found in every pool of stagnant water, and give it its green color, emit hydrogen during photosynthesis. But the prevailing explanation until today was that the hydrogen emission is very little, and therefore the algae cannot provide us with energy in useful quantities.

"Hydrogen is produced in algae with the help of an enzyme called hydrogenase, which breaks down in the presence of oxygen," explains Dr. Yacovi. "At night, without sunlight, the microalgae does not produce oxygen, and when the amount of oxygen decreases, a large amount of hydrogen is produced in the cell. The assumption until now was that for a few minutes at sunrise, upon exposure to sunlight, the algae emits both oxygen and hydrogen; But soon the oxygen accumulates and paralyzes the hydrogenase, and hydrogen production stops. We decided to test this assumption."

To their surprise, the researchers discovered that even in daylight, when the process of photosynthesis in algae produces a large amount of oxygen, a tiny amount of hydrogen is also emitted alongside it. From this they concluded that inside the algae there are areas where oxygen is absent, where the hydrogenase can work. "Subsequently, we found three effective mechanisms in the algae, which work non-stop to remove the oxygen from the cell, and allow hydrogenase to produce hydrogen continuously, throughout the hours of daylight," says Dr. Yacovi. "The implication is that microalgae have enormous, so far untapped, potential for hydrogen fuel production."

In the next step, the researchers used known technologies of genetic engineering to intervene in the photosynthesis system of the microalgae. Their goal was to make the cell produce a greater amount of hydrogen, at the expense of other processes, such as sugar production, thus driving increased production of hydrogen. In this way, they were able to engineer microalgae in the laboratory that produce 400% more hydrogen than the original algae.

"Approximately 20,000 years ago, the agricultural revolution took place: man stopped being a hunter-gatherer, domesticated varieties of plants from nature, and began growing his own food," concludes Dr. Yacovi. "But as far as energy is concerned, we still collect from nature what it provides us - so far mainly polluting fossil fuels, which are rapidly running out.

"Our discoveries are an important step on the way to another agricultural revolution, which may change the future of humanity: the production of clean energy in sufficient quantity, which will meet all our needs. In the laboratory we have produced microalgae strains with the potential for mass production of hydrogen, and now the challenge is to transfer these abilities to more resistant microalgae strains that live in nature. In other words, the goal is to domesticate wild strains of microalgae - just like man domesticated wild wheat for his needs. Then we will be able to grow the domesticated microalgae agriculturally, and they will provide us with hydrogen to fuel vehicles, and later also to drive the wheels of industry."

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