RESUMO
The present research evaluates the effects of three different lighting intensities, 60 (control), 30 and 120 µmol photons m- 2 s- 1 on Messastrum gracile growth. The observations indicated that a light intensity of 60 µmol photons m- 2 s- 1 resulted in higher cell density during experimental period. The light intensity of 120 µmol photons m- 2 s- 1 had a strong negative impact on M. gracile growth. Parameters such as lipid and protein content, cell density, chlorophyll-a and biomass were lower compared to the other light intensities. On the 14th and 21st growth days, the biomass, lipid and protein content were higher at 60 µmol photons m- 2 s- 1 with 800 mg L- 1, 5.7% and 34.4% biomass dry weight, respectively. The study also highlighted the economic aspects of M. gracile cultivation. The light intensities 30 and 60 µmol photons m- 2 s- 1 were found to be more advantageous than 120 µmol photons m- 2 s- 1 in terms of biomass, unit cost, lipid and protein content. Based on these findings, it was concluded that the light intensities of 30 and 60 µmol photons m- 2 s- 1 are more viable for M. gracile cultivation in laboratory under conditions used.
RESUMO
A laboratory culture of Ankistrodesmus gracilis algae was evaluated by studying the biology of the species and its chemical composition in a traditional medium (CHU12) and in two alternative culture media, NPK (20-5-20) and macrophyte (Eichhornia crassipes) + NPK, in three different types of recipients (fiberglass, carboy and plastic bag). First peak in the growth curve of Ankistrodesmus gracilis occurred on the ninth day in macrophyte + NPK medium (74.16 x 105 cells mL-1) in a fiberglass recipient. However, highest density (p < 0.01) was reported in medium CHU12 (122.87 x 105 cells mL-1) in a plastic bag on the twelfth day. Cell density was over 70 x 105 cells mL-1 starting on the twelfth day. Growth rate of A. gracilis was similar (p > 0.05) in culture media in the three recipients. Protein and fiber were similar (p > 0.05) in the treatments, but lipids were higher (p < 0.05) in NPK. Nitrate, ammonia, total phosphorus and orthophosphate contents were over 1 mg L-1 in NPK (p < 0.01). Results show that alternative media, such as NPK and macrophyte + NPK, are possible for large-scale culture of A. gracilis cultured in three types of recipients. Costs are low, occupying less space when cultured in plastic bags and in the laboratory.
O objetivo do estudo foi avaliar os aspectos biológicos e a composição química da alga Ankistrodesmus gracilis em laboratório utilizando um meio tradicional (CHU12) e dois meios alternativos, NPK (20-5-20) e macrófita (Eichhornia crassipes) + NPK em três diferentes tipos de recipientes (cuba de fibra de vidro translúcido, garrafões e saco plástico). O primeiro pico de densidade celular de Ankistrodesmus gracilis ocorreu no nono dia da curva de crescimento em meio macrófita+NPK (74,16 x 105 células mL-1) no recipiente de fibra de vidro, porém a maior densidade (p < 0,01) foi observada no meio CHU12 (122,87 x 105 células mL-1) em saco plástico no décimo segundo dia, a partir do qual a densidade celular permaneceu acima de 70 x 105 células mL-1. A taxa de crescimento de A. gracilis foi similar (p > 0,05) nos três recipientes e meios de cultivo. Os teores de proteína e fibra foram similares (p > 0,05) nos tratamentos utilizados, já os de lipídios foram mais elevados (p < 0,05) no meio NPK. Os teores médios de nitrato, amônia, fósforo total e ortofosfato estiveram acima de 1 mg L-1 no meio NPK (p < 0,01). Os resultados obtidos neste estudo indicam a possibilidade do uso de meios alternativos como o NPK e macrophyte +NPK para o cultivo de A. gracilis em larga escala cultivados nos três tipos de recipientes, porém, em saco plástico o custo é baixo e ocupa menos espaço em cultivo de laboratório.
