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Tetradesmus is a microalgal genus with biotechnological potential due to its rapid production of biomass, which is plenty in proteins, carbohydrates, lipids, and bioactives. However, its morphology and physiology need to be determined to guide better research to optimize the species cultivation and biocompounds processing. Thus, this study describes the biochemistry and morphology of the strain Tetradesmus obliquus BR003, isolated from a sample of freshwater reservoirs in a Brazilian municipality. In the T. obliquus BR003 dry biomass, we identified 61.6% unsaturated fatty acids, and 3.4% saturated fatty acids. Regarding other compounds, 28.50 ± 1.47 g soluble proteins/100 g, 0.14 ± 0.009 g carotenoids/100 g, 0.76 ± 0.013 g chlorophyll a/100 g, and 0.42 ± 0.015 g chlorophyll b/100 g with a chlorophyll a/b ratio of 1.8 were detected. The main chemical elements found were S, Mg, and P. The cells of BR003 were elliptically curved at the ends and without appendages. Histochemical tests showed carbohydrates distributed in the cytoplasm and pyrenoids, some lipid droplets, and proteins. The cytoplasm is rich in vacuoles, rough endoplasmic reticulum, mitochondria, and chloroplasts. The nucleus has a predominance of decondensed chromatin, and the cell wall has three layers. Chloroplasts have many starch granules and may be associated with a spherical central pyrenoid. To the best of our knowledge, this was the first biochemical description combined with ultrastructural morphological characterization of the strain T. obliquus BR003, grown under standard conditions, to demonstrate specific characteristics of the species.

The fatty acid's contents of non-conform pooled human milk can be affected by different processing and storage operational conditions. Besides, the knowledge of changes in the human milk fatty acid profile can help indicate its use in a given storage period, according to each newborn's specific need. Thus, in the present work, changes in the fatty acid profiles of three types of human milk (raw; pasteurized at 62.5 °C for 30 min; homogenized at 40 oC for 30 s followed by pasteurization) were studied during storage for six months in a freezer at -18 oC. Large variations were observed in the concentrations of polyunsaturated fatty acids, particularly of docosahexaenoic acid, with a reduction of almost 50% of its total. Palmitic and stearic acid contents also changed according to the conditions of processing and storage. Correlations between the decrease of long fatty acid chains and the increase of medium and short chains were verified. Thus, we observe that operational conditions of processing and storing change human milk lipid profile, with some nutritional losses.

Many countries have been experienced an increase in protein consumption due to the population growth and adoption of protein-rich dietaries. Unfortunately, conventional-based protein agroindustry is associated with environmental impacts that might aggravate as the humankind increase. Thus, it is important to screen for novel protein sources that are environmentally friendly. Microalgae farming is a promising alternative to couple the anthropic emissions with the production of food and feed. Some microalgae show protein contents two times higher than conventional protein sources. The use of whole microalgae biomass as a protein source in food and feed is simple and well-established. Conversely, the production of microalgae protein supplements and isolates requires the development of feasible and robust processes able to fractionate the microalgae biomass in different value-added products. Since most of the proteins are inside the microalgae cells, several techniques of disruption have been proposed to increase the efficiency to extract them. After the disruption of the microalgae cells, the proteins can be extracted, concentrated, isolated or purified allowing the development of different products. This critical review addresses the current state of the production of microalgae proteins for multifarious applications, and possibilities to concatenate the production of proteins and advanced biofuels.

The whole process of algae farming and biomass biorefining was evaluated on a pilot scale for the production of protein concentrate for poultry feeding and crude lipids. Scenedesmus obliquus was produced in open raceway ponds, and the cells were disrupted under low-pressure homogenization operating at 150 bar. Lipids were efficiently extracted using a hybrid multistage process based on a wet extraction using hexane and ethyl acetate, followed by dry extractions using hexane. The protein concentrate containing 43.1% of total proteins was recovered at low centrifugation of 400g and submitted to a desolventization process to remove residual hexane. The protein concentrate showed a similar composition of essential amino acids in comparison to soybean which is the main protein source used in feed formulation. Aspartic acid and glutamic acid were the main amino acids observed in the microalgal protein concentrate. As a feed supplement for broilers, the protein concentrate-based feed showed equal ingestion of the control, but the latter showed lower energy efficiency. The processing of 168 kg of wet biomass (14.8 kg on a dry weight basis) resulted in a production of 1.3 kg of crude lipids and 12.6 kg of protein concentrate, which corresponded to 93.7% of the total dry biomass.

Microalgae have attracted interest as a potential feedstock for biodiesel and valuable co-products such as bioethanol and protein. However, production at a commercial scale is still costly in part due to a lack of knowledge of their biology which in turn limits our ability to increase their overall growth rate or alter their metabolism and composition through changes in culture conditions or genetic engineering. We therefore isolated ten strains of freshwater microalgae (Chlorophyta) and characterized them at the morphological, molecular and biochemical level under autotrophic conditions. Two Scenedesmus strains (BR003 and BR024) differed from others strains in respect to their fatty acid profile, with high levels of C16 and C18:1 and low levels of polyunsaturated fatty acids. Interestingly, Chlamydomonas sp. BR020 and Chlorella vulgaris BR017 showed high levels of α-linolenic acid (C18:3), while BR017 also exhibited higher protein levels (14% of total dry weight), suggesting that these may be interesting strains to be used within the biorefinery concept. Furthermore, Monoraphidium sp. BR023 showed higher lipid content (29% of total dry weight), and transesterifiable fatty acid production (43.2 μg mg− 1 dry weight) and lower starch levels (164 μmol mg− 1 dry weight) while Chlamydomonas sp. BR020 exhibited the opposite trend. The results suggest that Scenedesmus bajacalifornicus BR024, Selenastrum capricornutum BR009 and Scenedesmus obliquus BR003 represent potential strains for biomass and biodiesel production, presenting 1.81, 1.73 and 2.14 mg mL− 1 dry weight of biomass, respectively, and 21.6, 16.4 and 17% of total dry weight of lipid, respectively. Additionally, the two Scenedesmus species showed the highest lipid productivity (23 mg L− 1 d− 1 and 24 mg L− 1d− 1). Overall we were able to access a new source of microalgal biodiversity and perform a robust characterization of native tropical microalgae strains leading to the identification of strains with high potential for biotechnological applications.

RESUMO: O desenvolvimento de equipamentos eficientes e específicos para a secagem de microalgas é essencial para a exploração comercial destes microrganismos que apresentam alta taxa de crescimento e grande potencial biotecnológico. Os custos de secagem da biomassa de microalgas ainda são elevados e precisam ser reduzidos para a produção de compostos com baixo valor agregado. Portanto, realizou-se o estudo da secagem da microalga Scenedesmus obliquus BR003 utilizando baixas temperaturas. S. obliquus BR003 é uma microalga robusta que apresenta alta produtividade de lipídeos. Em escala laboratorial, observou-se que a biomassa de S. obliquus BR003 foi rapidamente seca em baixas temperaturas entre 50 e 60 ºC. Um secador a gás foi utilizado para avaliar a secagem da biomassa de S. obliquus BR003 em escala piloto. A biomassa foi seca em menos de 24 h utilizando o secador a gás, entretanto, a elevada umidade da biomassa da microalga requereu uma maior renovação de ar na câmara do secador. A análise de fluidodinâmica computacional do secador a gás mostrou dois parâmetros importantes para se obter uma maior efetividade de transferência de calor e massa durante o processo de secagem da biomassa de microalga. Concluiu-se que um secador a gás adequado, para a biomassa de microalgas, deve possuir múltiplos pontos de injeção de ar, e um eficiente sistema de circulação e renovação de ar no interior da câmara de secagem. ABSTRACT: Development of efficient and specific equipment to dry microalgae is essential for commercial use of these microorganisms that show high growth rates and biotechnological potential. Drying costs of microalgae biomass are still high and they should be reduced for the production of compounds with low added value. Therefore, we evaluated the drying process of the microalga Scenedesmus obliquus BR003 using low temperatures. S. obliquus BR003 is a robust microalga that shows high lipid productivity. At laboratory scale, it was observed that the biomass of S. obliquus BR003 was rapidly dried at low temperatures between 50 and 60 ° C. A gas dryer was used to evaluate the drying of the biomass of S. obliquus BR003 on a pilot-scale. The biomass was dried in less than 24 h using the gas dryer; however, the high moisture of the microalga biomass required a higher air renovation in the drying chamber. Computational fluid dynamics analysis of the gas dryer showed two important parameters to achieve greater effectiveness of heat and mass transfer rates during the drying process of the microalga biomass. It was concluded that a gas dryer suitable for the microalgae biomass should have multiple air injection points, and an efficient circulation and renovation system of air inside the drying chamber.

The genus Scenedesmus harbors around 120 species, and some strains have been successfully used for mass culture and biotechnological applications. Considering the potential of this genus as a promising feedstock for production of biofuels, mainly biodiesel, it was evaluated the combined effects of trace elements, salinity stress and different cultivation modes (single batch, semi-continuous, and two-stage batch) on lipid productivity of the freshwater strains S. obliquus BR003 and S. bajacalifornicus BR024. Cultivation of BR003 and BR024 applying culture medium supplemented with trace elements and salt stress sustained a higher production of lipids. However, S. obliquus BR003 and S. bajacalifornicus BR024 showed different concentrations of neutral and total lipids when cultivated in batch-based and semi-continuous modes, and the batch-based modes were preferred for the production of lipids and carbohydrates. Consequently, different cultivation strategies coupled with slight salt stress improve the lipid productivity in Scenedesmus strains.

Experimental equilibrium data were obtained for aqueous two-phase systems composed of polyethylene glycol 400 g·mol–1 + sodium phosphate, and polyethylene glycol 400 g·mol–1 + sodium citrate, at T = (298.2, 308.2 and 318.2) K. For the system formed by sodium phosphate, at the studied range, the temperature effect on the position of the binodal curves was not relevant. For the system composed of sodium citrate, the temperature increase caused an expansion of the biphasic region. The efficacy of the salts in inducing phase segregation follows the order sodium phosphate > sodium citrate at temperatures of (298.2 and 308.2) K. Energy interaction parameters for the NRTL and UNIQUAC models were estimated, and the mean deviations between experimental and calculated compositions were 0.46 % and 0.32 %, respectively. These results show that both models, NRTL and UNIQUAC, are able to represent the phase behavior of polymer–salt aqueous two-phase systems evaluated.

The objective of this paper is to compare the lipid content and composition ofbiomass produced by a consortium of microalgae and bacteria, cultivated under different solar radiation intensities and tropical conditions in pilot-scale high-rate ponds (HRPs) using domestic sewage as culture medium. The treatment system consisted of an upflow anaerobic sludge blanket reactor followed by UV disinfection and six HRPs covered with shading screens that blocked 9%, 18%, 30%, 60% and 80% of the solar radiation. The total lipid content does not vary significantly among the units, showing a medium value of 9.5%. The results show that blocking over 30% of the solar radiation has a negative effect on the lipid productivity. The units with no shading and with 30% and 60% of solar radiation blocking have statistically significant lipid productivities, varying from 0.92 to 0.96 gm(-2) day(-1). Besides radiation, other variables such as volatile suspended solids and chlorophyll-a are able to explain the lipid accumulation. The lipid profile has a predominance of C16, C18:1 and C18:3 acids. The unsaturation of fatty acids increases with the reduction in solar radiation. On the other hand, the effect of polyunsaturation is not observed, which is probably due to the presence of a complex and diverse biomass.