Chlorella vulgaris as a lipid source: Cultivation on air and seawater-simulating medium in a helicoidal photobioreactor

The freshwater microalga Chlorella vulgaris was cultured batchwise on the seawater-simulating Schl\uf6sser medium either in a 1.1-L-working volume helicoidal photobioreactor (HeP) or Erlenmeyer flask (EF) as control and continuously supplying air as CO2 source. In these systems, maximum biomass concentration reached 1.65 +/- 0.17 g L-1 and 1.25 +/- 0.06 g L-1, and maximum cell productivity 197.6 +/- 20.4 mg L-1 d-1 and 160.8 +/- 12.2 mg L-1 d-1, respectively. Compared to the Bold\u2019s Basal medium commonly employed to cultivate this microorganism on a bench-scale, the Schl\uf6sser medium ensured significant increases in all the growth parameters, namely maximum cell concentration (268% in EF and 126% in HeP), maximum biomass productivity (554% in EF and 72% in HeP), average specific growth rate (67% in EF and 42% in HeP) and maximum specific growth rate (233% in EF and 22% in HeP). The lipid fraction of biomass collected at the end of runs was analyzed in terms of both lipid content and fatty acid profile. It was found that the seawater-simulating medium, despite of a 56-63% reduction of the overall biomass lipid content compared to the Bold\u2019s Basal one, led in HeP to significant increases in both the glycerides-to-total lipid ratio and polyunsaturated fatty acid content compared to the other conditions taken as an average. These results as a whole suggest that the helicoidal photobioreactor configuration could be a successful alternative to the present means to cultivate C. vulgaris as a lipid source