Synthetic biology for improved hydrogen production in <i>Chlamydomonas reinhardtii</i>
Samuel J. King, Ante Jerkovic, Louise J. Brown, Kerstin Petroll, Robert D. Willows
Abstract
Summary Hydrogen is a clean alternative to fossil fuels. It has applications for electricity generation and transportation and is used for the manufacturing of ammonia and steel. However, today, H 2 is almost exclusively produced from coal and natural gas. As such, methods to produce H 2 that do not use fossil fuels need to be developed and adopted. The biological manufacturing of H 2 may be one promising solution as this process is clean and renewable. Hydrogen is produced biologically via enzymes called hydrogenases. There are three classes of hydrogenases namely [FeFe], [NiFe] and [Fe] hydrogenases. The [FeFe] hydrogenase HydA1 from the model unicellular algae Chlamydomonas reinhardtii has been studied extensively and belongs to the A1 subclass of [FeFe] hydrogenases that have the highest turnover frequencies amongst hydrogenases (21,000 ± 12,000 H 2 s −1 for Ca HydA from Clostridium acetobutyliticum ). Yet to date, limitations in C. reinhardtii H 2 production pathways have hampered commercial scale implementation, in part due to O 2 sensitivity of hydrogenases and competing metabolic pathways, resulting in low H 2 production efficiency. Here, we describe key processes in the biogenesis of HydA1 and H 2 production pathways in C. reinhardtii . We also summarize recent advancements of algal H 2 production using synthetic biology and describe valuable tools such as high‐throughput screening (HTS) assays to accelerate the process of engineering algae for commercial biological H 2 production.