Heterotrophic utilization of ethylene glycol and propylene glycol by Chlorella protothecoides

This study explored the possibility of heterotrophic algal treatment of waste ethylene glycol (EG) and propylene glycol (PG) with simultaneous biomass production. Five Chlorella species were fed with EG and PG. With glycol-utilizing Chlorella species, the effect of pH was evaluated with pH-static cultures adjusted at pH 4.0, 5.5, 7.0, 8.5, and 10. Chlorella protothecoides was found to assimilate both EG and PG. The pH level had greater effects on the treatment of EG than PG, and drastic reduction of pH was observed in cultures with EG, probably owing to proton and organic acid generation during EG degradation. When pH was controlled within the range of 5.5-8.5, high EG removal efficiency (86%) was achieved. Although PG removal efficiency was low (30%), biomass yield from PG (0.52 gDW gPG(-1)) was found to be higher than that from EG (0.081 gDW gEG(-1)). The present study evaluated algal glycol assimilation quantitatively for the first time, and the results suggested potential future application of algal heterotrophic culture on glycol. (C) 2015 Elsevier B.V. All rights reserved.