Sergey G. Litvinets

Rhamnolipids solubilize oil contaminants in soils, making them more accessible for decomposition by soil microorganisms. Unlike chemical surfactants, rhamnolipids are environmentally friendly. The aim of this work is to obtain heterologous rhamnolipid producers based on Acetobacter aceti AlC1824 using an artificial promoter and optimize the producer cultivation conditions. This approach will avoid the use of highly effective biosurfactants of the opportunistic Pseudomonas aeruginosa species as a rhamnolipid producer, which can be used for soil bioremediation. The rhlAB gene cluster was amplified from the Pseudomonas aeruginosa B-6643 genome by polymerase chain reaction. A construct consisting of the rhlAB gene cluster and an artificial promoter was inserted into the p-AlT2 vector. The insert was introduced into Acetobacter aceti AlC1824 cells by calcium transformation. A total of 20 transformants were selected by blue-white selection. The target insert was detected in 7 transformants by polymerase chain reaction. The indicator test revealed a characteristic precipitate in two transformants: A4 and A8. Glucose, mannitol and glycerol were used as substrates. Suitable nitrogen and carbon sources were determined: peptone and mannitol, respectively. We found that the overall optimal pH of the medium was 5; the optimal cultivation temperature was 30 оC for A4 and 25 оC for A8. The amount of rhamnolipids formed by the above in optimal conditions is 139.3±20.1 mg/mL for transformant A4 and 13.0±1.0 mg/mL for transformant A8. The high washrhamnolipid emulsifying activity of heterologous producers in relation to crude oil has been experimentally demonstrated: EI24 for A4 was 93,9±1,5%, and for A8 – 96,7±1,5%.

Rhamnolipids are promising microbial glycolipid biosurfactants that can be used as preparations for soil bioremediation in oil pollution. The expression of the rhamnolipid biosynthesis gene cluster in the main producer, Pseudomonas aeruginosa, is regulated by quorum sensing signals (QS). Complex biosynthesis regulation does not allow achieving high product yields. The production of heterologous rhamnolipid producers is a promising way to overcome the complex QS-dependent regulation of rhamnolipid biosynthesis, and also avoids the use of opportunistic Pseudomonas aeruginosa for the industrial production of rhamnolipids. Heterologous Escherichia coli BLWT-based producers with a transformant E14 productivity of 3.40±0.96 g/L were obtained on the basis of the plasmid vector pAl2–T with a construct from the native promoter and rhlAB genes, and Pseudomonas viridiflava AlC1223-based ones with the productivity of transformants P5, P6, P8 332.00±0.10, 200.00±0.10 and 180.00±0.10 g/L, respectively. The presence of rhlAB genes in the expression vector allows the obtaining monorhamnolipids for further use as an agent for the solubilization of soil hydrophobic pollutant (e. g. petroleum products), which will intensify bioremediation processes.

The aim of the study was to develop ink enriched with a high content of lupine callus tissue (CT) suitable for 3D printing. Printable ink obtained using mashed potatoes (20 g/100 mL) and a 3% agar solution was used as the parent CT-free ink (CT0). Viscosity increased from 9.6 to 75.4 kPa·s during the cooling of the CT0 ink from 50 to 20 °C, while the viscosity of the ink with 80 g/100 mL of CT (CT80) increased from 0.9 to 5.6 kPa·s under the same conditions. The inclusion of CT was shown to decrease the hardness of 3D-printed food gel from 0.32 ± 0.03 to 0.21 ± 0.03 N. The storage modulus G’ value was 7.9 times lower in CT80 samples than in CT0 samples. The values of fracture stress for CT80 and CT0 inks were 1621 ± 711 and 13,241 ± 2329 Pa, respectively. The loss tangent and the limiting strain did not differ in CT0 and CT80, although the value of the fracture strain was 1.6 times higher in the latter. Thus, the present study demonstrates that CT may be added to printing ink in order to enhance food with plant cell material and enable the 3D printing of specially shaped foods.

The aim of the study is to develop and evaluate the printability of k-carrageenan inks enriched with callus tissue of lupin (L. angustifolius) and to determine the effect of two lupin calluses (LA14 and LA16) on the texture and digestibility of 3D-printed gel. The results demonstrated that the enriched ink was successfully 3D printed at concentrations of 33 and 50 g/100 mL of LA14 callus and 33 g/100 mL of LA16 callus. The feasibility of 3D printing is extremely reduced at higher concentrations of callus material in the ink. The hardness, cohesiveness, and gumminess of the 3D-printed gel with LA16 callus were weakened compared to the gel with LA14 callus. The results of rheological measurements showed that an increase in the content of LA16 callus interfered with the formation of a k-carrageenan gel network, while LA14 callus strengthened the k-carrageenan gel with increasing concentration. Gel samples at different concentrations of LA14 and LA16 calluses formed a spongy network structure, but the number of pores decreased, and their size increased, when the volume fraction occupied by LA14 and LA16 calluses increased. Simple polysaccharides, galacturonic acid residues, and phenolic compounds (PCs) were released from A-FP gels after sequential in vivo oral and in vitro gastrointestinal digestion. PCs were released predominantly in the simulated intestinal and colonic fluids. Thus, incorporating lupin callus into the hydrocolloid ink for food 3D printing can be a promising approach to developing a gelling material with new mechanical, rheological, and functional properties.

Изучена эффективность разработанного в интересах ПАО «Транснефть» твёрдого диспергента «Димэкс» для очистки поверхности воды от нефти и нефтепродуктов за счёт диспергирования, в том числе в зимних (ледовых) условиях. В качестве препарата сравнения использовали разрешённый для применения в России жидкий диспергент «Finasol OSR 52» производства компании «Total Fluides» (Франция). Показана возможность использования модифицированного теста Warren Spring Laboratory (WSL-тест) в качестве метода оценки эффективности диспергирования для твёрдых диспергентов. В условиях широкого диапазона изменяющихся параметров, включающих: солёность модельной морской воды, температуру воды, наличие шуги и битого льда, отношение диспергент:нефть, вид нефтепродукта показана высокая эффективность твёрдого диспергента «Димэкс», которая составила для средней сернистой нефти с плотностью 870,0 кг/м3 - 35,7-60,7%, для лёгкой, малосернистой нефти с плотностью 844,0 кг/м3 - 39,2-58,7%, для дизельного топлива с плотностью 830,8 кг/м3 - 50,7-72,2%, для керосина с плотностью 785,5 кг/м3 - 52,3-60,5%, для бензина с плотностью 739,2 кг/м3 - от 40,4 до 49,8%. Полученные значения сопоставимы со значениями для зарегистрированного на территории Российской Федерации жидкого диспергента «Finasol OSR 52», что позволяет рекомендовать твёрдый диспергент «Димэкс» для применения при ликвидации аварийных разливов нефти и нефтепродуктов на морских акваториях в условиях Севера. Ключевые слова твердый диспергент, жидкий диспергент, диспергирующая активность, нефть и нефтепродукты, бензин, керосин, дизельное топливо, метод оценки диспергирующей активности,...

The use of dispersants is an integral part of offshore oil spill contingency plans in various countries. In the Russian Federation, dispersants can be used in accordance with the document STO 318.4.02-2005. The document is of a recommendatory nature and provides for preliminary environmental studies as part of the procedures for the analysis of the total environmental benefit (Environmental Impact Assessment) with the passage of the State Environmental Expertise. The rules provide information on the dispersibility of some types of oil, the entry of which into the sea areas of the Russian Federation is most likely. In the absence of a certain oil product in the document, it is necessary to experimentally check their effectiveness, while there are no indications for the use of a specific method. In this regard, it is necessary to analyze the current state of this problem and its solutions in various countries. The paper summarizes the historically established experience of using laboratory methods for assessing the effectiveness of dispersants and testing approaches used in Europe and North America, analyzes their advantages and disadvantages. Various methods of quantitative assessment of the efficiency indicator of a dispersant and the factors that have the greatest influence on the dispersion process are considered, and the design features of a laboratory experiment are described. At the end of the work, the main recommendations are formulated that allow choosing a laboratory method for assessing the effectiveness of a dispersant with optimal characteristics and a general approach to testing.

The ability of bacterial strains of oil destructors of Pseudomonas fluorescens 28/5, Rhodococcus erythropolis 36a-1, Pseudonocardia autotrophica DSM 43096, 43190 and Rhodococcus jialingiae B-M-1 to produce biosurfactants was studied. The strains were cultured on liquid nutrient media containing dodecane, hexadecane and ethanol in a shaker incubator at 160 rpm, temperature (28 +/- 1) degrees C for 168 hours. We found that cultivation using dodecane and hexadecane causes the formation of conglomerates by all cultures on days 4-9. When grown on a synthetic nutrient medium with the addition of ethanol, the formation of conglomerates was not observed. The extraction of biosurfactants from the culture fluid was carried out by extraction with a mixture of chloroform and methanol and distillation of the solvents on a rotary evaporator. The volume of obtained surfactants ranged 0.15 to 1.90 mL from 10 mL of culture fluid. To analyze the chemical structure of biosurfactants, the method of high-performance liquid chromatography-mass spectrometry was used. Chromatograms obtained for all samples with positive polarity, as a result of comparison of chromatographic peaks, made it possible to establish an identical qualitative composition. The differences were only in the quantitative ratio of the individual components in different, samples. Chemical compounds related to nonionic surfactants and biosurfactants were found in the composition of the samples. The presence of carboxyl groups in all molecules was revealed, which allows these substances to be classified as surface anionic substances. The maximum amount of biosurfactant was obtained from strains of Pseudonocardia autotrophica DSM 43096, 43190 (15.2 g/L) and Rhodococcus erythropolis 36a-1 (14.4 g/L). This fact is the basis for the inclusion of these strains in the composition of biological products for the elimination of oil spills.