Screening and optimisation of hydrogen production by newly isolated nitrogen-fixing cyanobacterial strains

Abstract

Recently, there has been a propensity to postpone dealing with the world's climate concerns until later, resulting in a 1.5 °C rise in temperature over the last century. Therefore, interest in biologically derived, inexhaustible energy sources based on solar energy is growing. Cyanobacteria have the potential to produce clean, renewable fuels in the form of hydrogen (H<inf>2</inf>) gas, derived from solar energy and water. The current study reports the screening 11 cyanobacterial strains isolated from rice paddies and hotsprings for efficient H<inf>2</inf> producers. According to our findings, H<inf>2</inf> concentrations in the species ranged from 3.6 to 48.9 μmol mg−1 Chl a h−1. H<inf>2</inf> production by isolated species was shown to have a 2% positive influence on oxygen (O<inf>2</inf>) and carbon dioxide (CO<inf>2</inf>) concentrations and a 2% negative effect on all nitrogen gas (N<inf>2</inf>) concentrations. It was discovered that at high CO<inf>2</inf> concentrations, photosynthesis is enhanced but H<inf>2</inf> production is suppressed. Anabaena variabilis BTA-1047 was found to be the most active H<inf>2</inf>-producing species, with an H<inf>2</inf> production activity of 21.3 μmol mg−1 Chl a h−1. Moreover, a 1% O<inf>2</inf>: 2% CO<inf>2</inf> gas mixture doubled the strain activity of H<inf>2</inf> production. The findings of the study called into the question the notion that only an anaerobic environment is required for H<inf>2</inf> production by N<inf>2</inf>-fixing cyanobacterial species and explored whether H<inf>2</inf> productivity can be increased by stimulating the micro-anaerobic environment with a carbon source. © 2023 Elsevier B.V., All rights reserved.