On the Use of Agro-industrial Wastewaters to Promote Mixotrophic Metabolism in Chlorella vulgaris: Effect on FAME Profile and Biodiesel Properties

The increase of greenhouse gases into the atmosphere, mainly due to industrialization, has affected all the ecosystems. Current worldwide living standards are still heavily dependent on non-renewable fuels. The inevitable depletion of fossil fuels and the adverse climate changes push the scientific community to seek renewable and sustainable sources of fuel. In this scenario microalgae can be potentially exploited as renewable and environmentally friendly fuel resources. Wastewaters (WW) can be used as culture media minimizing the costs associated to their cultivation. Hence, the goal of this study was to examine the effect of agro-industrial WWs rich in organic nutrients on algal lipid content and fatty acid methyl esters (FAME) profile. For this purpose, the fresh water green algae Chlorella vulgaris was selected. This strain is able to thrive in a wide range of WWs with high biomass productivity and to shift its metabolism from autotrophic to hetero/mixotrophic one. C. vulgaris was cultivated in brewery (BWW), dairy (DWW), oil mill WWs and media supplemented with sugarcane molasses. High biomass yields were obtained when C. vulgaris was cultivated in BWW and DWW (1.76 g L-1 and 1.56 g L-1, respectively) compared to the control and the other WWs. The assessment of FAMEs composition (i.e. level of unsaturation) of algae cultivated under all the investigated conditions demonstrated that the former ones can be viably used as sources for producing biofuels.