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Almonte, Spain

Gomez-Jacinto V.,University of Huelva | Garcia-Barrera T.,University of Huelva | Garbayo-Nores I.,University of Huelva | Vilchez-Lobato C.,University of Huelva | And 2 more authors.
Chemical Papers | Year: 2012

The microalga Chlorella sorokiniana has been used to accumulate selenium and iodine from culture media enriched with these elements as a first stage in the production of supplemented foods. The microalgal colony was grown in a conventional culture medium containing iodine (KI) at concentrations in the range of 150-4000 μg mL-1. Similar experiments were performed with selenium (SeO 4 2- ) at concentrations in the range of 20-500 μg mL-1. The concentration of iodine and selenium in the culture medium was analytically monitored daily and the viability of the colony was checked by biomass concentration measurement and by evaluation of the total content of chlorophyll and carotenoids. In addition, photosynthetic activity and the number of cells were also monitored. Iodine accumulation in the algal biomass increased rapidly with time and reached a steady state after 4 h of exposure. With Se exposure the colony viability decreased, although the culture grew well with concentrations of the element of 50 μg mL-1 in the culture medium; this experiment produced Se-enrichment in the alga (3 μg g-1) within 100 h. Sequential extraction of an algal pellet was performed in order to separate Se compounds according to their affinity with the following solvents: hot water to recover low molecular mass Se species, enzymatic extraction with driselase for species associated with the cell wall, sodium dodecyl sulphate (SDS) for water insoluble selenoproteins and, finally, enzymolysis with lipase and pronase that release and fragment residual selenoproteinsproducing compounds with low molecular mass. Size-exclusion chromatography (SEC) coupled with an ICP-MS detector showed the preponderance of Se-containing molecules with low molecular mass, possibly seleno-amino acids. Only a peak of low intensity located at 10 min was observed in the SDS extract that could be associated with a protein with molecular mass of 67 kDa. Finally, analysis of the aqueous extract of alga by reverse-phase chromatography with inductively-coupled plasma mass-spectrometry (RPC-ICP-MS) detection revealed the presence of selenocysteine (SeCys2), selenomethylselenocysteine (SeMetSeCys), selenomethionine (SeMet), and Se(VI), particularly the last two species. © 2012 Institute of Chemistry, Slovak Academy of Sciences.

Gojkovic Z.,Brno University of Technology | Gojkovic Z.,University of Huelva | Garbayo-Nores I.,University of Huelva | Gomez-Jacinto V.,University of Huelva | And 4 more authors.
Process Biochemistry | Year: 2013

This article describes the enrichment of the fresh-water green microalga Chlorella sorokiniana in selenomethionine (SeMet). The microalga was cultivated in a 2.2 L glass-vessel photobioreactor, in a culture medium supplemented with selenate (SeO4 2-) concentrations ranging from 5 to 50 mg L-1. Although selenate exposure lowered culture viability, C. sorokiniana grew well at all tested selenate concentrations, however cultures supplemented with 50 mg L-1 selenate did not remain stable at steady state. A suitable selenate concentration in fresh culture medium for continuous operation was determined, which allowed stable long-term cultivation at steady state and maximal SeMet productivity. In order to do that, the effect of dilution rate on biomass productivity, viability and SeMet content of C. sorokiniana at several selenate concentrations were determined in the photobioreactor. A maximal SeMet productivity of 21 μg L-1 day-1 was obtained with 40 mg L-1 selenate in the culture medium. Then a continuous cultivation process at several dilution rates was performed at 40 mg L-1 selenate obtaining a maximum of 246 μg L-1 day-1 SeMet at a low dilution rate of 0.49 day -1, calculated on total daily effluent volume. This paper describes for the first time an efficient long-term continuous cultivation of C. sorokiniana for the production of biomass enriched in the high value amino acid SeMet, at laboratory scale. © 2013 Elsevier Ltd. All rights reserved.

Gojkovic Z.,University of Huelva | Gojkovic Z.,Brno University of Technology | Vilchez C.,University of Huelva | Vilchez C.,Algal Biotechnology Group | And 7 more authors.
The Scientific World Journal | Year: 2014

The aim of this work was to study the effect of Se(+VI) on viability, cell morphology, and selenomethionine accumulation of the green alga Chlorella sorokiniana grown in batch cultures. Culture exposed to sublethal Se concentrations of 40 mg·L-1 (212 M) decreased growth rates for about 25% compared to control. A selenate EC50 value of 45 mg·L-1 (238.2 M) was determined. Results showed that chlorophyll and carotenoids contents were not affected by Se exposure, while oxygen evolution decreased by half. Ultrastructural studies revealed granular stroma, fingerprint-like appearance of thylakoids which did not compromise cell activity. Unlike control cultures, SDS PAGE electrophoresis of crude extracts from selenate-exposed cell cultures revealed appearance of a protein band identified as 53 kDa Rubisco large subunit of Chlorella sorokiniana, suggesting that selenate affects expression of the corresponding chloroplast gene as this subunit is encoded in the chloroplast DNA. Results revealed that the microalga was able to accumulate up to 140 mg·kg-1 of SeMet in 120 h of cultivation. This paper shows that Chlorella sorokiniana biomass can be enriched in the high value aminoacid SeMet in batch cultures, while keeping photochemical viability and carbon dioxide fixation activity intact, if exposed to suitable sublethal concentrations of Se. © 2014 Živan Gojkovic et al.

Gojkovic Z.,University of Huelva | Gojkovic Z.,Brno University of Technology | Garbayo I.,University of Huelva | Ariza J.L.G.,University of Huelva | And 3 more authors.
Algal Research | Year: 2015

The complex role of selenium (Se) in living organisms can be assessed by studying physiological, biochemical and molecular aspects of its effects on lower organisms. This review aims to summarise the impact of Se on green algae (Chlorophyta), with regard to its uptake, bioaccumulation and toxicity. It will provide a better insight into the cellular response of algae to Se stress. The biochemical steps involved in the metabolism of accumulated Se are discussed based on the literature currently available on Se assimilation pathways in higher plants and marine phytoplankton. Se toxicity-discussed here using EC50 values-depends on its chemical form and concentration and it is species-specific in the case of algae. Most of the studies are particularly focussed on intracellular Se accumulation and biotransformation to Se-amino acids as a part of the detoxification process. Better understanding of the overall effect of Se on green algae is needed to help develop new technological applications for the production of Se-enriched biomass and valuable organic Se compounds from algae. © 2014 Elsevier B.V.

Vaquero I.,Algal Biotechnology Group | Vazquez M.,Algal Biotechnology Group | Ruiz-Dominguez M.C.,Algal Biotechnology Group | Vilchez C.,Algal Biotechnology Group
Journal of Applied Microbiology | Year: 2014

Aims: This study was aimed at increasing productivity of a novel lutein-rich acidic environment microalga, Coccomyxa onubensis, based on efficient inorganic carbon use. Methods and Results: Productivity was determined based on dry weight data; inorganic carbon concentration mechanisms were determined by means of carbonic anhydrase activity; carotenoids were extracted with methanol and measured by HPLC techniques. The existence of carbon concentration mechanisms and conditions that might lead to use them for addressing increased productivity of C. onubensis was studied. Best growth and carbon uptake capacity occurred at acidic pH, proving acid-tolerant behaviour of C. onubensis. Incubation in air followed by shift to high carbon conditions enhanced carbon-use efficiency in terms of growth rate and biomass productivity, based on the action of both carbonic anhydrase activities. Lutein accumulated in the microalga at high concentrations above 5-6 g kg-1 dry weight and did not depend on inorganic carbon conditions. Conclusions: Consequently, repeated cycles of air incubation and high CO2 incubation of C. onubensis might become a suitable tool to perform production processes of lutein-enriched biomass. Significant and Impact of the Study: This study intends to show that acidic environment microalgae can be produced at similar productivities of nonextreme microalgae, with the added advantage of their growth in highly selective culture medium. Particularly, it is applied to C. onubensis which accumulates lutein at commercially relevant concentrations. © 2013 The Society for Applied Microbiology.

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