The 1o3;1o6-E-D-glucan chrysolaminaran with molecular weight 8.5 kDa and 3.6:1 ratio of 1o3:1o6 bonds was isolated from cultivated diatom alga Synedra acus and characterized. It was shown that the isolated chrysolaminaran inhibited growth and colony formation of human colon tumor cells.Keywords: diatom alga, chrysolaminaran, 1o3;1o6-E-D-glucan, antitumor activity. Diatom algae are unicellular or colonial eukaryotic organisms that inhabit seas, oceans, and freshwaters and have adapted to habitats of plankton and benthos. Diatom algae and terrestrial plants are responsible for about 40% of the primary production on Earth [1]. Polysaccharides make up from 10 to 80% of the organic mass of diatoms [2, 3] and play an important role in their metabolism. Polysaccharides of diatom algae are divided into three groups depending on their location in the cell: storage, structural, and extracellular [4,5]. Each of these fulfills its own specific function.Storage polysaccharides are localized in vacuoles and represent the final photosynthesis products [6]. They are E-D-glucans, are called chrysolaminarans, and consist of short chains of 1o3-bonded E-D-glucopyranoses (n = 20-60) with branching at C6 and/or C2 [7-9].The study of polysaccharides from diatom algae is important for both an understanding of the functional processes of these organisms and their practical use. Analogs of chrysolaminarans, 1o3;1o6-E-D-glucans, isolated from yeast, fungi (lentinan), and culture filtrates of Schizophyllum commune (schizophyllan) have been used in cancer immunotherapy [10,11], act as immunomodulators, and increase the resistance to infections [12]. This makes them an attractive alternative to cytotoxic drugs. In contrast with other natural biopolymers, purified E-1,3-glucans retain their biological activity over time so that the mechanism of their action on the cellular and molecular level can be studied. It is currently known that the biological action of E-1,3-glucans is mediated through two membrane receptors, CR3 [13] and Dectin-1 [14].The biological activity of algae polysaccharides (laminarans and chrysolaminarans) has been studied less than that of glucans from yeast and fungi.Our goal was to isolate chrysolaminaran from cultivated diatom alga Synedra acus and to study its structure and antitumor activity.A chrysolaminaran preparation consisting of a polysaccharide-protein complex with a 1:8 protein:carbohydrate ratio was isolated from S. acus cultivated under laboratory conditions by extraction with hot water. According to the literature, the protein:carbohydrate ratio in similar complexes can vary from 0.33 to 6.5 depending on the physiological condition of the cell [15]. Removal of protein from the S. acus complex by the Sevage method [16] did not completely free the polysaccharide from the protein. A sample of the chrysolaminaran without protein could be obtained using hydrophobic chromatography over Polykhrom-1. The chrysolaminaran yield was 0.35% of the moist alga weight.

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Polycyclic aromatic hydrocarbons (PAHs) were detected in different types of PAH-containing samples collected in Lake Baikal during wildfires in the adjacent areas. The set of studied samples included the following: (i) water from the upper layer (5 m); (ii) water from the surface microlayer; (iii) water from the lake tributaries; (iv) water from deep layers (400 m); and (v) aerosol from the near-water layer. Ten PAHs were detected in the water samples: naphthalene, 1-methylnaphthalene, 2-methylnaphthalene acenaphthylene, acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene, and chrysene. The total PAH concentrations (ƩPAHs) were detected in a wide range from 9.3 to 160 ng/L, characterizing by seasonal, intersessional, and spatial variability. In September 2016, the ƩPAH concentration in the southern basin of the lake reached 610 ng/L in the upper water layer due to an increase in fluorene, phenanthrene, fluoranthene, and pyrene in the composition of the PAHs. In June 2019, ƩPAHs in the water from the northern basin of the lake reached 290 ng/L, with the naphthalene and phenanthrene concentrations up to 170 ng/L and 92 ng/L, respectively. The calculation of back trajectories of the atmospheric transport near Lake Baikal, satellite images, and ƩPAH concentrations in the surface water microlayer of 150 to 960 ng/L confirm the impact of wildfires on Lake Baikal, with which the seasonal increase in the ƩPAH concentrations was associated in 2016 and 2019. The toxicity of PAHs detected in the water of the lake in extreme situations was characterized by the total value of the toxic equivalent for PAHs ranging from 0.17 to 0.22 ng/L, and a possible ecological risk of the impact on biota was assessed as moderate.

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