The effect of 0.3 and 0.7 M NaCl on biomass yield, total nitrogen content, intracellular lipid content, and fatty acid profile of the lipids of the alga Botryococcus braunii IPPAS H-252 in different phases of the culture cycle was studied. The presence of sodium chloride in the medium inhibited the growth of algal cells for the first 3 days of the experiment, causing a decrease in total nitrogen, enhanced synthesis of triacylglycerols, and considerable changes in the lipid fatty acid profile: decreases in polyenoic acid contents (from 68.34% to 29.38% and 12.8%) and proportions of long-chain saturated acids (from 0.53% to 5.3% and 14.13% of the total fatty acids) at 0.3 M NaCl and 0.7 M NaCl, respectively. In later phases of the culture, at 0.3 M NaCl, the content of polyenoic acids rose to the values characteristic of the active growth phase of this alga. At 0.7 M NaCl, the proportion of polyenoic acids grew less significantly, but biomass concentration and total nitrogen increased, similarly to the experiment with 0.3 M NaCl.

INTRODUCTIONThe green alga Botryococcus braunii attracts attention because of its surprising ability to form a considerable amount of liquid hydrocarbons. Their composition is determined by the nature of a respective algal race (A, B, or L), and their content is believed to depend also on growth conditions [1]. Provision of biogenic elements, mainly nitrogen, is one of the main factors affecting algal metabolism. The change in the carbon/nitrogen ratio in a medium is known to result in a change in the directionality of metabolism. In many algae, an increase in this ratio results in an accumulation of neutral lipids, mainly triacylglycerols and/or carbohydrates [2][3][4][5] and is accompanied by considerable rearrangements in FA composition. These rearrangements consist in an increase in the content of saturated acids and a decrease in polyenoic acids [4,6,7]. Moreover, a decrease in the concentration of chlorophyll a accompanied by an increase in the content of carotenoids were noticed under the conditions of nitrogen limitation [8].Unfortunately, studies devoted to investigating the effect of nitrogen concentration on the biochemical composition of B. braunii are few in number and are mainly related to the production of hydrocarbons. For instance, a study showed that an increase in the nitrate content in a growth medium resulted in an increase in the duration of exponential phase of growth [9] and, consequently, in an increase in algal yield. In this case, the relative hydrocarbon content decreased; however, their total yield increased by 25% due to a higher biomass yield. On the contrary, culturing of the alga in a medium with decreased nitrogen content resulted in a decrease in both biomass and hydrocarbon content [10].Abstract -The effect of nitrogen limitation in a medium on the composition of intracellular lipids in the alga Botryococcus braunii Kütz IPPAS H-252 in the course of culture development was investigated. Under the conditions of nitrogen limitation, the alga under investigation accumulated lipids as triacylglycerols, and this process was accompanied by substantial changes in the total fatty acid (FA) composition, which were manifested in a decrease in trienoic acids (from 52.8-57.2 to 19.5-24.7% of total FAs) and an increase in the content of oleic (from 1.1-1.2 to 17.1-24.4%) and saturated (from 23.7-26.0 to 32.9-46.1%) acids. In the control culture, the directionality of FA redistribution was less marked, and these changes were noticed at the later stages of culture development. Under nitrogen limitation, marked changes in the FA composition of polar lipids occurred by the 13th day, and they were characterized by an increase in the content of saturated acids (up to 76.8%) and a dramatic decrease in the content of all polyenoic acids (up to 6.8%). The changes in the FA composition of triacylglycerols were noticed as early as by the 7th day; these changes consisted in an increase in the content of oleic acid, and its high content (28.4-38.4%) was maintained up to the end of culturing. In the cont...

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Experimental formulations of herbicide metribuzin embedded in matrices of degradable natural polymer poly(3-hydroxybutyrate) (P3HB) and its composites with poly(ethylene glycol) (PEG), poly-ε-caprolactone (PCL), and wood powder have been prepared in the form of pressed pellets containing 75% polymeric basis (pure P3HB or its composite with a second component at a ratio of 7:3) and 25% metribuzin. Incubation of formulations in soil laboratory systems led to the degradation of the matrix and herbicide release. The most active release of metribuzin (about 60% of the embedded herbicide over 35 days) was detected for the P3HB/PEG carrier compared to the P3HB, P3HB/wood, and P3HB/PCL forms (30-40%). Thus, the study shows that herbicide release can be controlled by the matrix formulation. Metribuzin formulations exerted a significant herbicidal effect on the plant Agrostis stolonifera, used as a weed plant model. Application of these long-term formulations will make it possible to reduce environmental release of chemicals, which will restrict the rate of their accumulation in trophic chains of ecosystems and abate their adverse effects on the biosphere.

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Biodegradable polymer poly(3-hydroxybutyrate) (P3HB) has been used as a matrix to construct slow-release formulations of the fungicide tebuconazole (TEB). P3HB/TEB systems constructed as films and pellets have been studied using differential scanning calorimetry, X-ray structure analysis, and Fourier transform infrared spectroscopy. TEB release from the experimental formulations has been studied in aqueous and soil laboratory systems. In the soil with known composition of microbial community, polymer was degraded, and TEB release after 35 days reached 60 and 36 % from films and pellets, respectively. That was 1.23 and 1.8 times more than the amount released to the water after 60 days in a sterile aqueous system. Incubation of P3HB/TEB films and pellets in the soil stimulated development of P3HB-degrading microorganisms of the genera Pseudomonas, Stenotrophomonas, Variovorax, and Streptomyces. Experiments with phytopathogenic fungi F. moniliforme and F. solani showed that the experimental P3HB/TEB formulations had antifungal activity comparable with that of free TEB.

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The synthesis and properties of polyhydroxyalkanoates (PHA) of different composition synthesized by Cupriavidus eutrophus B-10646 using glycerol as a carbon substrate were studied. In fed-batch culture in a 30-l fermenter the suitability of glycerol of various purification degrees for the synthesis of poly(3-hydroxybutyrate) P(3HB) with a 99.5, 99.7, and 82.07% content of the main substance was demonstrated. Purified glycerol (99.7%) was used for a 100-L pilot scale fermentation. The total biomass and P(3HB) yields were 110 and 85.8 g/L respectively after 60 h in fed-batch fermentation. An average productivity of P(3HB) was 1.33 g/L h The physical and chemical properties of P(3HB) synthesized on glycerol have changed: the degree of crystallinity and molecular weight decreased, but the temperature characteristics remain unchanged.