ABSTRACT
Monogalactosyldiacylglycerols (MGDGs) from microalgae containing a high proportion of polyunsaturated fatty acids (PUFAs) have enormous potential applications in various industries. In this study, the productivity and fatty acid composition of MGDGs from three microalgae in commercialized production, Chlorella sorokiniana GT, Nannochloropsis oceanica IMET1, and Arthrospira platensis, were evaluated under nitrogen-sufficient (+N) and nitrogen-deficient (-N) conditions. Under +N conditions, higher productivities of MGDGs from C. sorokiniana GT1, N. oceanica IMET1, and A. platensis were obtained with 16.3, 4.3, and 1.3 mg/L/day, respectively. In agreement with a high ratio of PUFAs in MGDGs, they accounted for 56%, 66%, and 47% of the total fatty acids in MGDG correspondingly. α-linoleic acid (ALA), eicosapentaenoic acid (EPA), and γ-linoleic acid (GLA) were the specific PUFAs of the three microalgae. The proportions of the specific PUFAs in MGDG accounted for 26%, 44%, and 63% of total specific PUFAs, respectively. Considering the production, cost of microalgae biomass and price of MGDG, the commercialized microalgae C. sorokiniana GT1 and A. platensis showed great potential to produce MGDGs with a high content of PUFAs, in contrast to N. oceanica IMET1, with its high biomass cost and low production. This study provides basic data for the extraction and separation of microalgae lipids from commercialized microalgae, which is helpful to promote the commercialization of microalgae.
Subject(s)
Chlorella/chemistry , Fatty Acids, Unsaturated/chemistry , Galactolipids/chemistry , Microalgae/chemistry , Spirulina/chemistry , Biomass , Biotechnology , Carbohydrates/chemistry , Fatty Acids , Lipids , Oryza/chemistry , Solid Phase Extraction , Spinacia oleracea/chemistryABSTRACT
Tetraselmis subcordiformis, a marine green alga, can produce hydrogen by photobiologically hydrolyzing seawater with hydrogenase. In this study, the preliminary purification of the enzyme was explored by ammonium sulfate precipitation, and the impact of sodium dithionite, beta-mercaptoethanol and glycerol on the enzyme stability during the process was investigated. The experimental results illustrated that sodium dithionite provided significant protection on the hydrogenase by depleting oxygen, while glycerol, a protectant against the structure instability of the enzyme, also presented protection. Crude enzyme with specific activity of 0.557 U/mg protein was extracted using 60%-70% saturated ammonium sulfate solution supplemented with 200 mmol/L sodium dithionite and 5% glycerol, and the hydrogenase recovery yield was about 30%.
Subject(s)
Ammonium Sulfate , Chemistry , Chemical Precipitation , Chlorophyta , Enzyme Stability , Hydrogen , Metabolism , Hydrogenase , Metabolism , SeawaterABSTRACT
Sponges (Porifera) are the oldest living metazoan in the world, among which most of them (Demospongia) can produce silicic skeleton from orthosilicic acid in the seawater under the natural enVironmental conditions. These biosilicic materials exhibit good mechanical and optical properties as well as good biocompatibility. During the biosilicification process of sponges, a protein, named as silicatein, plays an important role and has attracted great attention from biologist, chemists and material scientists. This mini review highlights the discovery of silicateins and its function as both an enzymatic catalyst and an organic template for biosilicification. The studies since 1999 were briefly introduced on the application of silicatein as a biocatalyst and template for synthesis of silica-based and other inorganic materials. It is expected to stimulate the interests in the related researches in China.
Subject(s)
Animals , Biocatalysis , Biocompatible Materials , Cathepsins , Chemistry , Porifera , Silicon Dioxide , MetabolismABSTRACT
Selenium is a trace element found in freshwater and the marine environment. We show that it plays a major role in spicule formation in the demosponge Suberites domuncula. If added to primmorphs, an in vitro sponge cell culture system, it stimulates the formation of siliceous spicules. Using differential display of transcripts, we demonstrate that, after a 72-h exposure of primmorphs to selenium, two genes are up-regulated; one codes for selenoprotein M and the other for a novel spicule-associated protein. The deduced protein sequence of selenoprotein M (14 kDa) shows characteristic features of metazoan selenoproteins. The spicule-associated protein (26 kDa) comprises six characteristic repeats of 20 amino acids, composed of 10 distinct hydrophobic regions ( approximately 9 amino acids in length). Recombinant proteins were prepared, and antibodies were raised against these two proteins. Both were found to stain the central axial filament, which comprises the silicatein, as well as the surface of the spicules. In the presence of selenium, only the genes for selenoprotein M and spicule-associated protein are up-regulated, whereas the expression of the silicatein gene remains unchanged. Finally we show that, in the presence of selenium, larger silica aggregates are formed. We conclude that selenium has a stimulatory effect on the formation of siliceous spicules in sponges, and it may be involved in the enzymatic synthesis of biosilica components.
