Kinetic and thermodynamic investigation of Arthrospira (Spirulina) platensis fed-batch cultivation in a tubular photobioreactor using urea as nitrogen source JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY, HOBOKEN, v. 87, n. 11, pp. 1574-1583, NOV, 2012 BACKGROUND: Fed-batch culture allows the cultivation of Arthrospira platensis using urea as nitrogen source. Tubular photobioreactors substantially increase cell growth, but the successful use of this cheap nitrogen source requires a knowledge of the kinetic and thermodynamic parameters of the process. This work aims at identifying the effect of two independent variables, temperature (T) and urea daily molar flow-rate (U), on cell growth, biomass composition and thermodynamic parameters involved in this photosynthetic cultivation.

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The effects of ultraviolet (UV) radiation on the skin, arising from sun exposure, have been explored since the previous century. Sunlight consists mainly of infrared (IR), visible, and UV radiation. UV region is divided into three subcategories, that is, UVC, UVB, and UVA. UVC (200-280 nm) is absorbed by the ozone layer in the stratosphere, while UVB and UVA (290-320 and 320-400 nm, respectively) reach the Earth's surface and influence human life and ecosystems. Consequently, human health may be affected under UV exposition. 1,2 In fact, UV exposure leads to health benefits such as production of cholecalciferol (vitamin D3), that is involved in functions

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“Vegan” and “sustainable” characteristics are strong claim trends behind the development of innovative skincare, fragrances, and makeup products. This created a need in the market for compliant ingredients. To date, there have been no records evidencing the use of the microalgae Neochloris oleoabundans (NA) in dermocosmetics. Therefore, we studied the applicability of such a natural compound in this context. NA was cultivated, and the scavenging activity (SA) of the NA extracts was evaluated. The highest SA was from the aqueous extract (54.8% ± 2.1%), being higher than that of the positive control. Two hydrogels were prepared with 1.0% ammonium acryloyldimethyltaurate/VP copolymer: (1) control gel; and (2) gel with a 1.0% NA aqueous extract. In vivo experiments were performed in healthy male and female volunteers with skin phototypes of II–IV. The stratum corneum (SC) hydration and the transepidermal water loss (TEWL) were measured in the forearm of participants to determine their biocompatibility. This parameter was determined by skin bioengineering measurements, confirming that SC hydration and TEWL were not affected by the samples. The laser Doppler measurements results showed a delayed erythema onset in the sites, where the NA hydrogel was applied. The results confirmed the biocompatibility and the anti-inflammatory activity of an innovative ingredient derived from microalgae suitable for a natural and vegan lifestyle.

Since cultivations of Arthrospira platensis have a high water demand, it is necessary to develop treatment methods for reusing the exhausted medium that may prevent environmental problems and obtaining useful biomass. The exhausted Schlösser medium obtained from A. platensis batch cultivation in bench-scale mini-tanks was treated by varying concentrations of different coagulants, ferric chloride (6, 10, and 14 mg L) or ferric sulfate (15, 25, and 35 mg L) and powdered activated carbon (PAC, 30 and 50 mg L). Such treated effluent was restored with NaNO and reused in new cultivations of A. platensis performed in Erlenmeyer flasks. Reusing media through the cultivation of A. platensis showed satisfactory results, particularly in the medium treated with ferric chloride and PAC. The maximum cell concentration obtained in the flasks was 1093 mg L, which corresponded to the medium treated with ferric chloride (6 mg L) and PAC (30 mg L). This cellular growth was higher than in the medium treated with ferric sulfate and PAC, in which values of maximum cell concentration did not exceed 796 mg L. The cultures in the media after treatment did not modify the biomass composition. Thus, combined coagulation/adsorption processes, commonly used in water treatment processes, can be efficient and viable for treating exhausted medium of A. platensis, allowing the production of such biomass with the reduction of production cost and saving water.

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Arthrospira platensis cultivation produces a saline spent medium that must be treated to allow its reuse, thus saving water and avoiding environmental pollution. This study evaluates the association of flocculation followed by adsorption to treat the spent medium by applying different concentrations of granular activated carbon (GAC) and ferric chloride (F), and using different residence times (T). The simultaneous optimization of the independent variables GAC, F, and T was performed using both a 23 central composite design and a response surface methodology. The cells cultivated in the medium obtained after the optimal conditions of treatment (GAC = 54.2 g L−1, F = 10.0 mg L−1, and T = 30.8 min) provided the highest maximum cell concentration, Xm = 3140 ± 77 mg L−1 in 0.5 L Erlenmeyer flasks with the highest protein biomass content (44.9%). The treated medium in such conditions was also used in a 3.5 L tubular photobioreactor (PBR), reaching Xm = 4033 ± 110 mg L−1 and biomass with high contents of both protein (47.3 ± 2.6%) and chlorophyll (9.7 ± 0.3 mg g dry cell−1). Therefore, this study can contribute to diminishing costs of A. platensis production by reusing its culture medium and improving its biomass quality in PBRs.