Haematococcus pluvialis cultivation and astaxanthin production using different nitrogen sources with pulse feeding strategy

The microalga Haematococcus pluvialis has astaxanthin as the most economically valuable compound. However, there are challenges related to its cultivation and low biomass productivity. Therefore, the present study proposes a change in the nitrogen supply mode, through the pulse feeding strategy, and the use of different N sources to increase the biomass of H. pluvialis and astaxanthin production. The two-factor experimental design had factor 1 (three sources of nitrogen-NaNO3, NH4NO3, and (NH2)(2)CO) and factor 2 (nitrogen feeding strategy-pulse feeding (PF) and without pulse feeding (WPF)). Nitrogen source of the BBM (NaNO3) was replaced by NH4NO3 or (NH2)(2)CO, maintaining the original [N] in WPF, while in PF, N sources were added by pulses. The results of growth variables showed a significant difference for maximum cell density, with higher values for NaNO3-PF (176 x 10(4) cell mL(-1)) and (NH2)(2)CO-PF (165 x 10(4) cell mL(-1)). Yield and biomass productivity in the vegetative and cystic phases were higher for cultures in PF. Higher N content was found in the PF medium, providing greater cell reproduction; however, excess of nitrogen after the exponential growth phase limits carotenogenesis. The contents and concentrations of total carotenoids and astaxanthin, in general, were higher in NH4NO3-WPF (astaxanthin content similar to 23 mg g(-1)) being influenced by nitrogen depletion and pH variation. Thus, nitrogen pulse feeding strategy provided higher biomasses of H. pluvialis, and the decrease in the pulses concentrations can result in higher astaxanthin production due to the lower N residue.