The reaction catalyzed by bacterial luciferase is also an oxidative process:
* FMNH + O + RCHO → FMN + RCOOH + HO + light
In the reaction, molecular oxygen oxidizes flavin mononucleotide and a long-chain aliphatic aldehyde to an aliphatic carboxylic acid. The reaction forms an excited hydroxyflavin intermediate, which is dehydrated to the product FMN to emit blue-green light.
Nearly all of the energy input into the reaction is transformed into light. The reaction is 80% to 90% efficient.  In comparison, the incandescent light bulb only converts about 10% of its energy into light and a 150 lumen per Watt (lm/W) LED converts 20% of input energy to visible light.