Arthrospira platensis biomass with high protein content cultivated in continuous process using urea as nitrogen...

Arthrospira platensis has been studied for single-cell protein production because of its biomass composition and its ability of growing in alternative media. This work evaluated the effects of different dilution rates (D) and urea concentrations (N(0)) on A. platensis continuous culture, in terms of growth, kinetic parameters, biomass composition and nitrogen removal.

Arthrospira platensis was continuously cultivated in a glass-made vertical column photobioreactor agitated with Rushton turbines. There were used different dilution rates (0·04-0·44 day(-1)) and urea concentrations (0·5 and 5 mmol l(-1)). With N(0) = 5 mmol l(-1), the maximum steady-state biomass concentration was 1415 mg l(-1), achieved with D = 0·04 day(-1), but the highest protein content (71·9%) was obtained by applying D = 0·12 day(-1), attaining a protein productivity of 106·41 mg l(-1) day(-1). Nitrogen removal reached 99% on steady-state conditions.

The best results were achieved by applying N(0) = 5 mmol l(-1); however, urea led to inhibitory conditions at D ≥ 0·16 day(-1), inducing the system wash-out. The agitation afforded satisfactory mixture and did not harm the trichomes structure.

These results can enhance the basis for the continuous removal of nitrogenous wastewater pollutants using cyanobacteria, with an easily assembled photobioreactor.