Dietary supplementation of cattle manure in Scenedesmus acuminatus algae suspension in daphnia magna farming

The use of live food has been recommended in the larval stage of several species of fish, providing better survival and growth results when compared to those obtained with artificial diets. This study aims to evaluate the biomass and protein content of Daphnia magna submitted to three diets: Diet A (Scenedesmus acuminatus) at a concentration of 1.5x107 cells/mL per individual, diet B (cattle manure) at 6.5g/L, and diet C at the same diets and concentration as in diets A and B for a period of 21 days. The experiment was repeated three times, totaling 63 days of study with a completely randomized design, with three replicates in each treatment. The experimental unit consisted of polyethylene containers with 20L, containing 10 D. magna neonates. Every two days, temperature, pH, dissolved oxygen and saturation were measured. At the end of the experimental period, nutrient quantification of the culture water and diets (phosphorus, nitrate, ammoniacal nitrogen, total nitrogen, and organic nitrogen), determination of the final biomass and protein content of the individuals were performed. Diet C provided a higher mean biomass value, followed by diet A and B, with values ​​of 344.12 g, 157.71 g and 81.93 g, respectively. The D. magna fed with diet B had a higher protein content, with 2.56%, followed by those fed diets C and A, with 2.17 and 1.32%, respectively. At the end of the experiment, it was found that the organisms fed diet C had a larger reproduction rate when compared to the other diets.

Statistical study of growth kinetics and lipid content of microalgae grown in brackish waters for bioenergetic purposes

This study aimed to statistically prove the influence of salinity on growth kinetics and intracellular lipid accumulation in microalgae. The species Chlorella sp., Scenedesmus acuminatus, Nannochloropsis sp., Monoraphidium contortum and Pediastrum tetras were studied, which were isolated in the Brazilian semi-arid region and cultivated in synthetic media with the addition of NaCl. From the crops, growth kinetics, dry biomass production and lipid content were analyzed, using the experimental planning for one factor as a tool, with the NaCl concentration as an independent variable. The kinetic parameters maximum growth speed (µmax) and generation time (tg), as well as lipid concentration were the response variables studied. The results showed that, in the species Scenedesmus acuminatus, Nannochloropsis sp. and Pediastrum tetras, salt stress contributed to the increase in µmax and the consequent decrease in tg. The highest levels of lipid accumulation were obtained in Nannochloropsis sp. (62.04%), in the medium with the highest salinity and Pediastrum tetras (54.04%) in the lowest. Dry biomass production was higher in Scenedesmus acuminatus (1,941.37 mg.L-1) and Nannochloropsis sp. (1237.05 mg.L-1), both at a concentration of 4.0 g.L-1. Therefore, saline stress acted directly on the cell growth and lipid content of the species, which can be used as a device to enhance lipid production for the purpose of producing biofuels.

Trophic Transition Enhanced Biomass and Lipid Production of the Unicellular Green Alga Scenedesmus acuminatus

Microalgal heterotrophic cultivation is an emerging technology that can enable producing high cell-density algal cell cultures, which can be coupled with photoautotrophic cultivation for valuable chemicals such as lipids manufacturing. However, how the heterotrophically grown algal cells respond to the lipid-inducing conditions has not been fully elucidated so far. In this study, when the heterotrophically grown Scenedesmus acuminatus cells were subjected to the high light (HL) and nitrogen-limited (NL) conditions, both the biomass and lipid productivity were enhanced as compared to that of the photoautotrophically grown counterparts. The chlorophyll a fluorometry analysis showed that the Fv/Fm and Y(II) of the heterotrophically grown cells subjected to the HL and NL conditions was recovered to the maximum value of 0.75 and 0.43, respectively, much higher than those of the photoautotrophically grown cells under the same stress conditions. Transcriptomic analysis revealed that heterotrophically grown cells fully expressed the genes coding for the photosystems proteins, including the key photoprotective proteins D1, PsbS, light-harvesting-complex (LHC) I and LHC II. Meanwhile, downregulation of the carotenoid biosynthesis and upregulation of the glycolysis/gluconeogenesis, tricarboxylic acid (TCA) cycle and oxidative phosphorylation pathways were observed when the heterotrophically grown cells were subjected to the HL and N-limited conditions for lipid production. It was deduced that regulation of these pathways not only enhanced the light utilization but also provided the reducing power and ATP by which the biomass accumulation was significantly elevated. Besides, upregulation of the acetyl-CoA carboxylase/biotin carboxylase, digalactosyl diacylglycerol synthase and diacylglycerol acyltransferase 2 encoding genes may be attributable to the enhanced lipid production. Understanding the cellular responses during the trophic transition process could guide improvement of the strength of trophic transition enhancing microalgal biomass and lipid production.

Draft Genome Sequence of the Green Alga Scenedesmus acuminatus SAG 38.81

ABSTRACT Scenedesmus acuminatus, also known as Tetradesmus acuminatus, is a promising green microalga for sustainable production of microalga products, including valuable compounds such as astaxanthin, β-carotene, and lutein, polysaccharides such as β-glucan, and polyunsaturated fatty acids. Here, we report the draft whole-genome sequence of Scenedesmus acuminatus SAG 38.81.

BIOTECHNOLOGICAL POTENTIAL OF PSEUDOKIRCHNERIELLA SUBCAPITATA, SCENEDESMUS SPINOSUS, AND SCENEDESMUS ACUMINATUS

Microalgae are promising alternatives to sequestration of carbon and reduction of environmental problems, e.g. the greenhouse effect and industrial water pollution. Depending on the growth conditions, microalgae can differ in their metabolism products, leading them to grow at different rates. Intracellular reactions and nutritional requirements from cell metabolism, as well as biomass composition, may vary in function of the temperature. In this study, the biotechnological potential of three microalgae strains from the species was evaluated in terms of growth, biomass composition, fatty acid profile, and chlorophyll and carotenoids contents. Each of the three species demonstrated different potential depending on their metabolisms: Scenedesmus spinosus presented fastest growth and had the highest protein content (52.99%), Pseudokirchneriella subcapitata presented the highest content of lipid extracted (26.51%), and Scenedesmus acuminatus showed increased production of chlorophyll (5.25 mg l–1) and carotenoid (1.02 mg l–1) pigments.

Manejo de macrófitas proveniente de infestação em ambientes naturais como suplemento para produção da microalga de interesse econômico Scenedesmus acuminatus

Este estudo avaliou a influência de seis meios de cultura alternativos (um a base de NPK, dois contendo extrato de Pistia stratiotes e Eichhornia crassipes enriquecido de NPK, e outros três com diferentes diluições de extrato puro de E. crassipes, (Eic 40, Eic 85, Eic 130) em comparação ao meio de cultura comercial ASM-1, no desenvolvimento da microalga Scenedesmus acuminatus. Foram avaliados taxa de crescimento (K), densidade, volume celular, biovolume e qualidade nutricional dos meios de cultura. Os meios de culturas testados apresentaram concentração de nutrientes suficiente para o crescimento da microalga. As taxas de crescimento de ASM-1 (0,439) foram similares (p>0,05) a NPK, Pis + NPK e Eic + NPK. Eic 85 e Eic 130 apresentaram os valores mais baixos (0,201; 0,150, respectivamente) e similares entre si. Os volumes dos tratamentos não diferiram de ASM-1 (135,427 μm3), somente o Eic NPK e Eic 130 apresentaram valores menores (86,780 e 100,401 μm3, respectivamente). O maior biovolume e densidade celular foram encontrados em Eic NPK (1,273 mm3.L-1 e 1047 x 104 cél.mL-1). Os tratamentos apresentaram capacidade de nutrição muito similar ao ASM-1, podendo substitui-lo no cultivo de S. acuminatus, em especial Eic + NPK que apresentou maior densidade e biovolume. Os tratamentos com extrato puro, apesar de apresentarem resultados mais baixos, ainda assim possibilitaram o desenvolvimento da alga.