Oskar Fields, Elsie Cunliffe, Ellis C O'Neill
Until now, only five photoactive pigments have been identified in Euglena gracilis and there has been contradictory reporting of the major carotenoid. The impact of various environmental factors on the carotenoid content of E. gracilis has not been well studied. Using an improved HPLC UV-VIS method, combined with mass spectrometry, we have now identified 12 photoactive pigments from E. gracilis extracts and confirmed diadinoxanthin as the major carotenoid produced in E. gracilis. After testing cultivation media and major carbon sources (addition of glucose-2-20 g/L, ethanol-0.2%-2.0% w/v), we found that EG: JM with 0.8% ethanol increased diadinoxanthin relative production by 361% (4.29 mg/L) when compared to standard cultivation (EG media, 24 h light, PPFD 25.9 μmol/m2/s and 25°C). This investigation also tested a range of light intensities (PPFD 0-41.7 μmol/m2/s) and found that increasing light intensity (PPFD to 41.7 μmol/m2/s) increased diadinoxanthin production by a further 36% (5.82 mg/L), giving an increase of 489% over the standard cultivation conditions.