They then have nowhere to put all the light energy they are absorbing, and the resulting breakdown of biochemical pathways creates toxic oxygen-containing molecules known as free radicals.
The next trick, which Exxon's money will help pay for, is to tweak the biochemical pathway that makes the algal oil (which is known, technically, as a triglyceride, and has oxygen atoms in it as well as carbon and hydrogen) so that the oxygen-containing parts of the molecules are snipped off and a pure hydrocarbon is left.
In 96 tiny wells robotic arms mixed variations of molecules containing nitrogen, oxygen and sulphur with metals such as zirconium, titanium and hafnium.