A research team in the USA has developed a new sorghum variant that outperforms soyabeans in oil production.To meet growing demand for renewable fuels like sustainable aviation fuel (SAF) and renewable diesel, research has been undertaken into creating new sustainable sources of vegetable oils, known as triacylglycerols (TAG).The research team at the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI) said most TAG was currently provided by oil palm and oilseeds, such as soyabeans, but these sources could not meet future global consumption.
To address this, high-biomass grasses like sorghum - which are highly efficient at photosynthesis and can grow in tough climates - have been engineered to produce oil. In their new study, published in Plant Biotechnology Journal, CABBI scientists focused on a lab-to-field pipeline to deliver sorghum high in TAG.
The team developed sorghum which could accumulate up to 5.5% dry weight TAG in its leaves and 3.5% dry weight in its stems under field conditions – 78 times and 58 times higher levels than in unmodified sorghum, respectively.
With this level of production, the sorghum variety could provide about 1.4 times more oil/ha than soybeans, the researchers said.“This work … demonstrates how fundamental research can be used to develop new crop feedstocks to address global energy demands,” Edgar Cahoon, director of the Center for Plant Science Innovation at the University of Nebraska and one of the corresponding authors on the paper, said.
Unlike oil-rich seeds and fruit from plants like oil palm, TAG typically only accumulates in a plant’s vegetative organs (leaves and stems) as a stress response to membrane damage. To develop sorghum for vegetative oil accumulation, the researchers used a ‘push-pull-protect’ strategy, which CAABI researchers had used previously to increase vegetative oil accumulation in other plants.
The team then introduced genes to ‘push’ more carbon from photosynthesis into oil production, ‘pull’ fatty acids into TAG molecules and ‘protect’ the stored oil from breaking down.
This approach built on the team’s previous work with other crops, focusing on sorghum for its heat and drought tolerance and well-understood genome.
Using advanced gene transfer methods, CABBI scientists engineered sorghum lines that maintained stable oil production over multiple generations and also avoided the biomass reductions seen in similar studies with other biomass crops.
The research team said they would continue to study ways to further increase oil yields to meet CABBI’s goal of growing crops that are 10% TAG by dry weight.“Further improvement of TAG yields will depend on in-depth analysis of the effects of the ‘push-pull-protect’ metabolic engineering approach applied in the study,” Jörg Schwender, senior scientist of the Plant Science Group at Brookhaven National Laboratory and corresponding author on the paper, said.
