Since the last time we spoke with Yield10 Bioscience, the company has continued to advance its work on scaling plant-based PHA production through the Camelina platform. Sustainable Plastics had a quick chat with Yield10’s Chief Science Officer & VP of research, Kristi Snell, about the latest paper the company published in the Plant Biotechnology Journal describing a new technology solution for deploying the PHB pathway in Camelina.
Kristi, can you briefly explain the advancement described in the new paper?
Yes, so, basically, we have substantially improved the viability of the polymer producing plants. In previous work that we've done, which was also published in the same journal back in 2015, we reported great success in producing very high levels of polymer in the plants - up to 15% of the seed - but the seedlings were very impaired. They were unable to thrive once planted in the soil.
In the present paper, we show how we have re-engineered the polymer synthesis in the Camelina plant so that we can get both good levels of polymer production and viable seeding seedlings. These plants will actually grow in the field and seeds with polymer can be harvested. This is a pretty big step in the commercialisation of biopolymer production in plants.
It’s a pretty unique approach, isn’t it?
Well, 15 years ago, maybe, there were a lot of people working on biopolymer synthesis and plants, and specifically PHA synthesis and plants. While most were in academia, there were a few companies working in the field as well. However, it is quite difficult to do, and there really not that many people doing it anymore. We've stuck with it. We have the metabolic engineering capabilities to really figure out what the issues are, and to systematically go and solve them. We are now getting results.
If I understand correctly, you’ve now re-engineered the plants so that the polymer granules produced don’t interfere with other processes in the plant?
Yes: the polymers consists of small, discrete granules and the idea is that they can sequester themselves and not interfere with anything in the plant. That is probably what went wrong before. The seed has different compartments, called organelles, and so with our new strategy, we changed compartments, so, the site, of polymer synthesis. And I think we had less interference when we did that. In our previous attempts, we had been producing it in the same compartment that photosynthesis occurs, and that was probably an issue.
You now have plants that actually are viable in the field. Can they survive in summer and winter?
We have done this in both winter and spring lines. We did our first field testing winter lines relatively recently, but both lines are doing well. However, we still have some further technology development to do before commercialising this. We want to increase the level of polymers in the plants and we want to even make them even better economically. But we are on the right track.
When you say increase the levels, what levels are you at now and where do you want to be?
in the greenhouse, we showed 10% production. That was the level that we produced and reported in the paper. We would like to get up to 20% in the seed. We need to perform a little bit more metabolic engineering: metabolic pathway engineering to really reroute carbon to try to get the levels up. So we're still some ways off.
Is it easy for farmers to grow camelina?
Camelina grows very well, both in the spring and in the winter. It grows on marginal soils and it's incredibly drought tolerant. We have started our first commercial planting - so just normal Camelina -to get growers used to growing the crop. The feedback has been excellent. Ultimately, we want our polymer producing lines to be just as easy to grow as conventional Camelina, so, eventually, we want to engineer herbicide tolerance into the lines, to ensure the farmer has a crop that is just like everything else that he's used to growing. Once it is also able to tolerate herbicides, the farmer can just integrate into his current crop rotations and be able to grow it like a normal crop,
Can you indicate any kind of timeline – so when do you expect to be able to commercialise PHA?
I don't think I can publicly give you a timeline right now. But, as I said, we do have another round of engineering to improve the polymer levels in the plants and achieve herbicide tolerance. That in itself will take a couple of years. We still consider this project in to be in the research and development phase, which means we're still a bit off from producing commercial levels of polymer.
The market is waiting impatiently for an affordable PHA polymer - with affordable referring to well under the eight euros per kilo it costs now. It might be too early to ask about that now, but – do you think this will be possible?
We believe it will, with especially with PHB, which would be our first product. PHB -polyhydroxybutyrate – is the simplest PHA. We think it could easily be used as a cheap source of polymer that could be blended with other polymers to improve their properties. That would really be the first target of our program: blending with other polymers, creating a very cheap source of a renewable completely biodegradable polymer on the market.
Kristi Snell, Ph.D. is an industry-recognized expert in metabolic engineering of plants and microbes for the production of novel products and increased plant yield.