Microalgae have been recently recognized as a promising alternative for the effective treatment of anaerobic digestion effluents. However, to date, a widely applied microalgae-based process is still absent, due to several constraints mainly attributed to high ammonia concentrations and turbidity, both hindering microalgal growth. Within this scope, the purpose of the present study was to investigate the performance of two Chlorella strains, SAG 211-11b and a local Algerian isolate, under different nitrogen levels, upon ammonia stripping. The experiments were performed on cylindrical photobioreactors under controlled pH (7.8 ± 0.2) and temperature (25 ± 2 °C). Cultures were monitored for biomass production and substrate consumption. After sampling at the beginning of the stationary phase of growth (12th day) and after the maturation of the cells (24th day), an analysis of the produced biomass was conducted, in terms of its biochemical components. The local isolate grew better than C. vulgaris 211-11b, resulting in 1.43 mg L⁻¹ biomass compared to 1.02 mg L⁻¹ under 25 mg NH₄-N L⁻¹, while organic carbon and nutrient consumption varied between the two strains and different conditions. Concerning biomass quality, a high initial NH₄-N concentration led to high protein content, while low nitrogen levels favored fatty acid (FA) accumulation, though the production of pigments was inhibited. In particular, the protein content of the final biomass was determined close to 45% of the dry weight in all experimental scenarios with adequate nitrogen, while proteins decreased, and the fatty acids approached 20% in the case of the local isolate grown on the substrate with the lowest initial ammonium nitrogen (25 mg NH₄-N L⁻¹). The novelty of the present work lies in the comparison of a microalga with industrial applications against a local isolate of the same species, which may prove to be even more robust and profitable.

This study investigates the use of cheese whey to enhance the microalgae cultivation for bioenergy and coproducts in the framework of circular economy and pollution attenuation. A local isolated indigenous Chlorella vulgaris strain using a growth medium containing BG11 and cheese whey (BG11/CW) was used. Algae density, dry weight, organic carbon consumption, biochemical composition, fatty acid profile, Total pigments were investigated. The best growth is obtained in the BG11/CW culture media, with a dry biomass and cell density of 2.5 g/L, 6.5×107 Cells/ml, respectively. This represents 5 times the dry biomass obtained in the BG11medium (0.45 g/L, 1.68×107 cells/ml). Indigenous Chlorella vulgaris growth is favored by glycose availability after lactose degradation with a consumption of 62% on the 7th day. Pigments content was improved with an average value of 34.5 mg/gDW and 9 mg/mgDW for total chlorophylls and carotenoids, respectively. Chlorella vulgaris cultivation on BG11/CW has showed a high protein content with a value of 46%. Indigenous Chlorella vulgaris was able to accumulate a suitable lipid content that could reach 23%, which are rich in C16:00, C18:00, C18:1. This strain is a potential candidate for a sustainable bioenergy and coproducts that could contribute efficiently to promote the circular economy.