Engineering oilseeds to synthesise designer wax esters

Waxes are a type of lipid which have useful properties, specially as lubricants. The modern industrial world is dependent (literally) on the smooth running of millions of machines and processes, all of which require lubricants to reduce friction and wear & tear. Currently, most lubricants are made from crude oil by chemical transformations, a process which consumes this deminishing natural resource both as a feedstock and as a source of energy to drive the reaction. In other words, petrochemically-derived lubricants are unsustainable. Whilst plant seeds produce oils, these are not very effective as lubricants as they are prone to oxidising which makes them sticky. However, one particular plant, jojoba, makes a different class of oil to that found in all other plant seeds. Jojoba seeds accumulate wax esters, rather than triacylglycerols, and waxes have far superior lubricating properties compared with the normal seed oils. Unfortunately, jobaba plants only grow in American deserts, which precludes their use in European agriculture. To circumvent this problem, we propose to transfer the genes for wax biosynthesis from jojoba (and other organisms which make wax esters) to suitable plant species for evaluation and testing. It is proposed to use Arabidopsis as a model system to identify the best combination of genes to make waxes with the most useful properties, and having determined these, introduce them into a dedicated industrial oilseed crop, Brassica carinata (Ethiopian mustard). Importantly, by using a crop species that is not used to produce food, this will ensure that our waxes (to serve as biolubricants) will not enter the human food chain. Overall, this project aims to demonstrate the feasablity of substituting plant-derived wax esters for petrochemically-derived lubricants, providing a new green, sustainable source of these important compounds.

The aim of this project is to synthesise novel wax esters in the seeds of transgenic plants. Wax esters have superior lubricant properties to plant-derived triacylglycerols, and could therefore serve as a green replacement for the chemical esters derived from mineral oil which are currrently extensively used as industrial lubricants. Only one plant species (jojoba) is known to synthesise wax esters in seeds, though the aerial surface of higher plants is normally covered with epicuticular waxes. This project proposes to reciprocally express a small panel of wax biosynthetic genes (from a range of organisms) to generate novel wax esters. We will also seek to generate wax esters with enhanced chemical diversity. This will be achieved by the co-expression of the primary wax biosynthetic genes (fatty acyl-CoA reducase, wax synthase) with enzyme activities which will modulate the common substrate pool (acyl-CoAs) for these two enzymes. Such activities will include a thioesterase to generate medium chain fatty acyl-CoAs, an elongating activity to synthesise very long chain acyl-CoAs and a fatty acyl hydroxylase to introduce hydroxyl groups into the substrates. Thus, this project is taking a limited synthetic biology approach to the generation of novel waxes which could serve as new and improved biolubricants. Such as source of novel lipids could also serve as chemical feedstocks for other applications. Importantly, demonstration of the accumulation of seed wax esters in a (GM) oilseed crop will be carried out in the non-food (industrial) crop Brassica carinata, precluding the possibility that these novel lipids could enter the human food chain.

As described in the Impact Plan, there is a well-established route at Rothamsted for maximising exploitation and impact of our research. The PI has considerable experience in this area, specifically in the field of plant lipid metabolism and biotechnology. It is recognised that within the terms of the IBTI Club conditions that there are some restrictions on the use and exploitation of results and IP outside the Club, and this is recognised in the Impact Plan and by the appropriate officers within Rothamsted