Synthetic Biology Approaches To Enhance Microalgal Productivity

The major bottleneck in commercializing biofuels and other commodities produced by microalgae is the high cost associated with phototrophic cultivation. Improving microalgal productivities could be a solution to this problem. Synthetic biology methods have recently been used to engineer the downstream production pathways in several microalgal strains. However, engineering upstream photosynthetic and carbon fixation metabolism to enhance growth, productivity, and yield has barely been explored in microalgae. We describe strategies to improve the generation of reducing power from light, as well as to improve the assimilation of CO2 by either the native Calvin cycle or synthetic alternatives. Overall, we are optimistic that recent technological advances will prompt long-awaited breakthroughs in microalgal research. The high cost of microalgal cultivation has hindered exploitation of their advantages for sustainable production of green chemicals and biomass. Nevertheless, recent advances in the field of synthetic biology could help to overcome the associated bottlenecks.Improving reducing power generation and carbon influx will be crucial for attaining an overall improvement in microalgal productivity.Enhancing light absorption, in conjunction with techniques to swiftly channel electrons through the electron transport chain, could enhance the generation of reducing power.The Calvin–Benson–Bassham (CBB) cycle might not be the best CO2 fixation pathway, and other natural and synthetic pathways may outperform the CBB cycle. However, implementing these entire pathways in new hosts will be very challenging.Mixotrophic cultivation and microbial electrosynthesis could be implemented as an additional source of energy and carbon to improve microalgal productivity.