I read that Japanese researchers have developed very sensitive camera that recorded bioluminescence in humans; is it possible and if so what is the mechanism behind it?
From the article you linked:
virtually all living organisms emit extremely weak light, spontaneously without external photoexcitation. This biophoton emission is categorized in different phenomena of light emission from bioluminescence, and is believed to be a by-product of biochemical reactions in which excited molecules are produced from bioenergetic processes that involves active oxygen species
They reference these two works. The first is a 1988 review from Popp et al. (1988):
Biophoton emission - Experientia 44:543–600. (sorry, I cannot find the link to a full text...)
The second work they reference is by the same first author:
Finally, a search in Pubmed reveals various other articles by different authors studying different species.