Nifty episode... I could bio-engineer myself to go way, way beyond being a vegan. I did get hung up on the terminology of the Janists being being classified as autotrophs. Sigh, no.
I was trying to figure out where the protagonist was getting her supply of Carbon (as she's a C-based life-form). She's utilizing photons water, and carbon dioxide. Okay. And she's excreting oxygen (or perhaps her body metabolizes the oxygen in some kind of cellular respiration feedback loop) & carbon-containing-high-energy compounds.
My author's creation must have figured out how to unlink photosynthesis, respiration, and even the Carbon cycle (a biogeochemical cycle).