Влияние различных источников азота в питательной среде на рост зеленой микроводоросли Chromochloris zofingiensis в накопительной культурестатья
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Дата последнего поиска статьи во внешних источниках: 10 июня 2020 г.
Аннотация:The effect of three nitrogen (N) sources in the nutrient medium – sodium nitrate (NaNO₃), urea
(CO(NH₂)₂), and ammonium chloride (NH₄Cl) – on the morphological and physiological characteristics
of the green microalga Chromochloris (Chlorella) zofingiensis, a potential commercial producer of lipids and of a ketocarotenoid astaxanthin, was studied. The alga was batch-cultivated in glass conical flasks from starting cell density (n) around 2.3·10⁶ per mL and dry weight (DW) content of 0.06 g·L⁻¹ in all variants at 120 μmol·m⁻²·s⁻¹ PAR, +20…+21 °C, and air bubbling at a rate of 0.3 L·min⁻¹·L⁻¹. The concentration of nitrogen sources (as elemental N) in the modified BBM nutrient was 8.83 mmol·L⁻¹, the cultivation duration was 17 days. The dynamics of n and cell volumes, DW content, chlorophylls a and b (Chla and Chlb), total carotenoids (Car), and lipids (Lip) in the cultures, concentration of N sources in the nutrient medium and its pH were recorded. It was shown that the growth rate, size distribution of the cell populations and the biomass chemical composition depended significantly on the nitrogen source in the nutrient medium. Using NH₄Cl as N source caused on the second day growth inhibition, cell swelling, aggregation, and discoloration and, by the seventh day, culture crash. The cells of C. zofingiensis took up NaNO₃ and CO(NH₂)₂ from the medium at a similar rate (0.626 and 0.631 mmol N·L⁻¹·day⁻¹, respectively), but the growth of the culture fed with CO(NH₂)₂ lagged, its cell volume and Chla, Chlb,and total Car contents declined profoundly. The average dry matter productivity (PDW) in the culture grown on CO(NH₂)₂ [(0.086 ± 0.004) g·L⁻¹·day⁻¹] was 32.6 % lower than in the culture grown on NaNO₃ [(0.114 ± 0.005) g·L⁻¹·day⁻¹]. At the same time, lipid productivity (PLᵢ) of the urea-fed culture was comparable with that of the nitrate-fed culture (PLᵢ = 28 and 26 mg·L⁻¹·day⁻¹, respectively). The lipid DW percentage of the former exceeded significantly that of the nitrate-fed culture (31.6 % vs 23.1 %, respectively). From the standpoint of profitability, the lag in biomass accumulation recorded in the urea-fed culture on PDW is not critical since it is compensated by lowering the cost of nitrogen source for the nutrient medium (approximately by 230 %) and a higher biomass lipid content. C. zofingiensis grown in media
with urea as the only N source deserves further investigation.