RESUMO
Arthrospira platensis was cultivated in tubular photobioreactor in order to evaluate growth and biomass production at variable photosynthetic photon flux density (PPFD = 60, 120, and 240 µmol photons m(-2)s(-1)) and employing three different systems for cell circulation, specifically an airlift, a motor-driven pumping and a pressurized system. The influence of these two independents variables on the maximum cell concentration (X(m)), cell productivity (P(x)), nitrogen-to-cell conversion factor (Y(X/N) ), photosynthetic efficiency (PE), and biomass composition (total lipids and proteins), taken as responses, was evaluated by analysis of variance. The statistical analysis revealed that the best combination of responses' mean values (X(m) = 4,055 mg L(-1), P(x) = 406 mg L(-1)day(-1), Y(X/N) = 5.07 mg mg(-1), total lipids = 8.94%, total proteins = 30.3%, PE = 2.04%) was obtained at PPFD = 120 µmol photons m(-2)s(-1); therefore, this light intensity should be considered as the most well-suited for A. platensis cultivation in this photobioreactor configuration. The airlift system did not exert any significant positive statistical influence on the responses, which suggests that this traditional cell circulation system could successfully be substituted by the others tested in this work.
Assuntos
Técnicas de Cultura de Células/instrumentação , Fotobiorreatores , Spirulina/crescimento & desenvolvimento , Spirulina/metabolismo , Análise de Variância , Carga Bacteriana , Biomassa , Cinética , Luz , FotossínteseRESUMO
Arthrospira platensis was cultivated in tubular photobioreactor using different photosynthetic photon flux densities (PPFD) and protocols of (NH4)2SO4 fed-batch supply. Results were evaluated by variance analysis selecting maximum cell concentration (X(m)), cell productivity (P(x)), nitrogen-to-cell conversion factor (Y(X/N)) and biomass, protein and lipid contents as responses. At PPFD of 120 and 240 µmol-photons/m² s, a parabolic profile of (NH4)2SO4 addition aiming at producing biomass with 7% nitrogen content ensured X(m) values (14.1 and 12.2 g/L, respectively) comparable to those obtained with NaNO3. At PPFD of 240 µmol-photons/m² s, P(x) (1.69 g/Ld) was 36% higher, although the photosynthetic efficiency (3.0%) was less than one-half that at PPFD of 120 µmol-photons/m² s. Biomass was shown to be constituted by about 35% proteins and 10% lipids, without any dependence on PPFD or kind of nitrogen source. These results highlight the possible use of (NH4)2SO4 as alternative, cheap nitrogen source for A. platensis cultivation in tubular photobioreactors.