Plants are large and thirsty. They require a lot of space and if you want to extract something from them you’ll have to find a way to efficiently extract it from the smorgasbord of chemicals in each and every plant cell. And for that matter plant cells are not all equal, and you may find plenty of product in one cell type but precious little in others.
With all that in mind it seems a pretty great idea to take desirable metabolic pathways out of plants and get them working in friendly microbes such as E. coli and budding yeast. And that is precisely what many synthetic biology/ metabolic engineering groups do as their bread and butter. If this is news to you just check out some of the articles below:
and of course there was the flagship synbio project, taking the enzymes for the biosynthesis of anti-malarial drug Artemisinin from Artemisia annua into yeast. That work spawned a company, Amyris, in California. Whilst over on the East Coast of the USA Ginko Bioworks follow a similar strategy.
So if microbes are so great, why use plants at all?
Well, perhaps to extract the power for metabolism from photosynthesis?
Still no dice. There are plenty of photosyntheic mircoorganisms (Cyanobacteria and unicellular eukaryotic algae such as Chlamydomonas).Birger Lindberg Møller’s group at the University of Copenhagen are turning the chloroplasts of microalgae and mosses into biorefineries.
So what are the advantages of leafy plants?
Actually there are several. But here are the three most currently relevant:
You can eat them. Think Golden Rice and Purple Tomatoes.
They are cheap to grow. Sunlight and rainwater are free. So is soil, and if you nurture it properly and grow nitrogen fixers in rotation expenditure on fertilizers can be kept down. By contrast, micro-organisms need constantly aerated (or artificially anoxic) environments, that need to be supplied with the right nutrients whilst being protected from contamination. All that adds up to running costs, which have been a major stumbling block in the way of algal biofuel production, for example. So if you want to produce vast amounts of a relatively low-value product plants are likely the best way to go.
Tobacco is an efficient soluble protein producing machine. This has spawned a huge amount of research focus into harnessing tobacco for the production of bio-pharmaceuticals and ‘plantibodies’.
Taking plant pathways into microbes is a neat trick, and one that definitely makes sense. But there is still plenty of reason to hold on to our leafy friends.