A genetically engineered strain of alga produces twice as much lipid as the wild parent, but can grow at a similar rate, reports a paper published online this week in Nature Biotechnology. These findings are a step along the path to eventual commercialization of sustainable microalgal-derived biofuels.

The idea of using fats and oils produced by phototrophic microalgae - microscopic organisms that can produce lipids when grown using light, water and CO2 - to produce biodiesel that can supplement petroleum-based transport fuels has been actively investigated since the late 1970s. To date, efforts to engineer microalgae to produce more lipids have been restricted to industrial strains that do not make sufficient amounts for commercialization. The industrial microalga Nannocholoropsis gaditana can make up to six times more lipid than lab strains, but despite decades of research, any improvements in lipid productivity of Nannocholoropsis sp. have been accompanied by crippled growth, and the commercial promise of this genus has remained unfulfilled.

Eric Moellering and colleagues used several engineering tools, including CRISPR-Cas9 gene editing, to identify ZnCys, which regulates accumulation of lipids in industrial strains of N. gaditana. The authors modified ZnCys and found that this doubled lipid productivity - to up to five grams per meter per day - while permitting growth at nearly equivalent rates to the parental, unmodified strain’s. Understanding how to increase lipid production of microalgae while retaining their ability to grow is an advancement toward a microalgal phototrophic production process for lipids that would remove the need for biodiesel to be reliant on sugars produced by land-grown plants.