Effect of organic carbon and nutrient supplementation on the digestate-grown microalga, Parachlorella kessleri.

Digested effluents are usually deprived of the appropriate levels of organic carbon or macro- and micro-nutrients to effectively sustain microalgal growth. In this regard, Parachlorella kessleri was cultivated in an agro-waste digestate supplemented with different glucose concentrations, magnesium and trace metals and alternatively with cheese whey (CW), with view to enriching digestate with organic and inorganic constituents and decreasing freshwater demand. Between the conditions tested, CW addition resulted in the highest biomass concentration, 2.68 g L-1 within 18 days of cultivation. Chlorophyll content significantly decreased under 5 g L-1 glucose addition, in contrast to MgSO4 co-addition and CW supplementation. The latter also induced high photosynthetic activity and better-preserved vitality of the photosynthetic apparatus, compared to sole glucose addition. Concerning lipid accumulation, in the presence of high glucose concentration, % of total fatty acids decreased, and the saturated fraction increased over polyunsaturated fatty acids (PUFAs).