Led by Szilvia Tóth, the Momentum Molecular Photobioenergetics Group of the ELKH Biological Research Centre in Szeged (BRC) has developed a new and trend-setting process for the sustainable production of hydrogen using hydrogen-producing green algae. A paper presenting their recent results was published in Bioresource Technology, a leading biotechnology journal.

The transition to a carbon neutral and circular economy has recently become one of the main strategic directions of the European Economic Area. The use of hydrogen as an energy source is at the heart of developing a net zero CO2 economy. Today, hydrogen is largely produced from natural gas, which inevitable causes huge CO2 pollution. In the future, it is expected that the excess energy produced by solar and wind power plants will be stored in the form of hydrogen obtained from water splitting through electrolysis.

However, hydrogen gas can also be produced directly from the energy of sunlight. Green algae are able to produce hydrogen as a by-product of photosynthesis, using their hydrogenase enzymes found in chloroplasts. The hydrogenases in green algae are very efficient, but they are sensitive to the oxygen produced during photosynthesis, so in nature, the process of hydrogen production lasts only for a few minutes. This specificity has been a major obstacle to the economic exploitation of biohydrogen production. Over the past 30 years or so, researchers have tried a number of methods to lengthen the process of hydrogen production, but it was possible only with significant cell damage.

Research into the efficiency and sustainability of hydrogen production from green algae has made significant progress in recent years. The BRC Momentum Molecular Photobioenergetics Group has developed a new, trend-setting method that is much more efficient and sustainable than the previous ones, and it is promising for industrial-scale applications, thanks to its simplicity.

Recent developments involve the placement of a thin layer of highly concentrated algal culture in a suitable photobioreactor (Nagy et al. 2021). The culture is kept in the dark for a few hours to express hydrogen-producing enzymes, and then it is exposed to light. Thereafter, the algae produce hydrogen gas from water over a period of several days.

From a bio-industrial point of view, it is important to point out that hydrogen production can be sustained at sunlight intensities without significant damage to algae cultures. The new process has increased output by a factor of around ten compared to previous methods. In certain photosynthetic mutants, the hydrogen production process is even more stable and the output is significantly higher. A by-product is the formation of economically valuable biomass, and the algae use carbon dioxide during their growth phase.

The researchers aim to further increase output, as well as design a prototype of a photobioreactor capable of producing H2 in the field. Previous research results are protected by a European patent (Nagy V and Tóth SzZ PCT/EP2018/053115).

Publication:

Valéria Nagy, Anna Podmaniczki, André Vidal-Meireles, Soujanya Kuntam, Éva Herman, László Kovács, Dávid Tóth, Alberto Scoma, Szilvia Z. Tóth (2021) Thin cell layer cultures of Chlamydomonas reinhardtii L159I-N230Y, pgrl1 and pgr5 mutants perform enhanced hydrogen production at sunlight intensity. Bioresource Technology 333: 125217.