Towards Increasing the Global Supply of Oil from Terrestrial Plants for Industrial Applications

Randall J. Weselake

Alberta Innovates Phytola Centre, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5

The current global production of vegetable oil is about 177 million metric tonnes with demand at close to 173 million metric tonnes. The top four oil-producing crops include palm, soybean, oilseed rape (including canola) and sunflower. As our global population steadily increases, we will be challenged to provide sufficient plant oil for food, feed and industrial applications. In terms of terrestrial plants, seeds and mesocarp tissue are currently the major sources of plant oils. Triacylglycerol (TAG), which is the major component of plant oil, represents one of the most energy-rich forms of reduced carbon suitable for use in lubricants and the production of a range of industrial chemicals and polymers. Although plant breeding has led to steady increases in the seed oil content of major oilseed crops, recent metabolic engineering studies have demonstrated that modest increases in seed oil content can be obtained by up-regulation and/or down-regulation of specific biochemical reactions in lipid biosynthesis and processes involved in carbon-partitioning (Weselake et al., 2009, Biotechnol Adv 27:866-878; Woodfield et al., 2015, Inform 26:78-83). Typically vegetative tissues produce only very low levels of TAG, although there are some examples of plant species which accumulate substantial TAG in stems and tubers. Within the last decade, great advances were made in reprogramming vegetative tissue to accumulate substantial levels of TAG which could potentially provide new sources of plant biomass for industrial applications and high-energy animal feed. Recently, tobacco was engineered to produce more than 15% (dry weight) TAG in leaves without severe effects on plant development (Vanhercke et al., 2014, Plant Biotechnol J 12:231-239). When extrapolated to a field situation, this level of oil from vegetative tissue would exceed the oil yield per acre typically obtained from conventional oilseed crops. Metabolic engineering of high biomass C4 crops such as sugarcane or switchgrass to produce increased TAG in vegetative tissue, or poplar to produce TAG in stems, has the potential to produce even greater levels of oil for industrial applications.