Biostimulant Capacity of and Species Produced Using Wastewater and Centrate.

The aim of the present study was to assess the potential of producing four microalgal strains using secondary-treated urban wastewater supplemented with centrate, and to evaluate the biostimulant effects of several microalgal extracts obtained using water and sonication. Four strains were studied: UAL-1, sp. UAL-2, UAL-3, and UAL-4. The highest biomass productivity was found for , with a value of 0.38 ± 0.01 g·L·day. UAL-1 achieved a biomass productivity of 0.31 ± 0.03 g·L·day (the highest for the genus), while the N-NH, N-NO, and P-PO removal capacities of this strain were 51.9 ± 2.4, 0.8 ± 0.1, and 5.7 ± 0.3 mg·L·day, respectively. UAL-1 showed the greatest potential for use as a biostimulant-when used at a concentration of 0.1 g·L, it increased the germination index of watercress seeds by 3.5%. At concentrations of 0.5 and 2.0 g·L, the biomass from this microalga promoted adventitious root formation in soybean seeds by 220% and 493%, respectively. The cucumber expansion test suggested a cytokinin-like effect from UAL-1; it was also the only strain that promoted the formation of chlorophylls in wheat leaves. Overall, the results of the present study suggest the potential of producing UAL-1 using centrate and wastewater as well as the potential utilisation of its biomass to develop high-value biostimulants.