Αρχειοθήκη ιστολογίου

Αλέξανδρος Γ. Σφακιανάκης
ΩτοΡινοΛαρυγγολόγος
Αναπαύσεως 5
Άγιος Νικόλαος Κρήτη 72100
2841026182
6032607174

Τρίτη 1 Δεκεμβρίου 2020

Use of an Alternative Pathway for Isoleucine Synthesis in Threonine-Producing Strains of Escherichia coli

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Abstract

An E. coli strain in which all known pathways of threonine catabolism were inactivated (Δtdh, ΔltaE, ΔilvA, ΔtdcB, ΔyiaY) has been constructed. It was shown that the expression of heterologous citramalate synthase from Leptospira interrogans in an E. coli strain carrying the ΔilvA deletion can serve as an alternative pathway for isoleucine synthesis. It was observed that cimA overexpression has a negative effect on threonine production. We developed a system for regulated gene expression based on the inducible promoter PLtetO and TetR, a repressor of the tetracycline operon. The threonine-producing strain B-1201, in which the cimA gene is expressed under the control of the regulated promoter, was constructed. When the B-1201 strain was cultivated in a fermenter, a correlation was established between the threonine productivity and the expression level of th e cimA gene, and the optimal inductor content for the maximum threonine accumulation was also determined.

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Assessment of the Biotechnological Potential of Cyanobacterial and Microalgal Strains from IPPAS Culture Collection

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Abstract

A search for strains capable of the simultaneous production of high amounts of several biologically valuable compounds and/or high biomass productivity has been carried out. The growth characteristics and biochemical composition of 12 microalgal and cyanobacterial strains from the IPPAS Collection were studied at the exponential and stationary growth phases. All of the strains had high growth rates (a doubling time of 6–22 h). The strains Cyanobacterium sp. IPPAS B-1200, Chlorella sp. IPPAS C-1210, Nannochloris sp. IPPAS C-1509, Cyanidium caldarium IPPAS P-510, and Vischeria sp. IPPAS H-242 demonstrated the highest biotechnological potential and can be used for the production of various types of biofuel, pigments, and feed and food additives, including those with a high content of eicosapentaenoic acid (20 : 5 Δ5, 8,11, 14, 17).

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New Recombinant Phytase from Kosakonia sacchari : Characteristics and Biotechnological Potential

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Abstract

A DNA sequence from Kosakonia sacchari that, according to automated computer analysis, is believed to correspond to the gene for histidine-acid phytase has been selected from the GenBank database. The sequence was optimized for codon composition, synthesized, cloned, and expressed in Pichia pastoris. The main characteristics of the purified recombinant enzyme were determined. It was established that a pH of 4.5 and a temperature of 50°C are optimal for phytase functioning. The specific activity, Michaelis constant (Km), and maximum reaction rate (Vmax) with phytate as a substrate were 1470 U/mg, 193 μM and 2167 μmol/(min mg), respectively. It was shown that the enzyme was characterized by a wide range of working pH levels. Therefore, due to its properties, this new recombinant phytase can be considered a high-potential enzyme for agrobiotechnology.

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Obtainment and Characteristics of Phytoecdysteroid-Producing Аjuga turkestanica (Rgl.) Plant Cell Cultures

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Ajuga turkestanica (Rgl.) Briq. (Lamiaceae) callus cultures were obtained from a wild plant, and the morphogenesis processes in these cultures were studied. It was possible to obtain gemmogenesis or rhizogenesis in the first six to eight growth cycles, depending on the hormonal composition of the medium; the capacity for morphogenesis was lost after 10–15 growth cycles. Suspension cell cultures were initiated from some calluses with strong growth. As a result, about 100 calluses and suspension plant cell lines of A. turkestanica were obtained; a number of them were characterized in terms of growth rate and were analyzed via HPLC-MS for the presence of phytoecdysteroids. 20-Hydroxyecdysone and turkesterone were found in most of the studied lines; the content of the first compound in the most productive lines was 30–50 times higher than in the second (2.0–2.5 mg/g versus 0.04– 0.05 mg/g dry weight, respectively). An increase i n the phytoecdysteroid content in plant cells cultured in vitro was observed by the end of the growing cycle. However, phytoecdysteroids were not found in many of the obtained plant cell lines. Further research is needed to clarify the causes of the presence or absence of phytoecdysteroids in A. turkestanica plant cell cultures.

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Effect of Virus-Inactivating Agents on the Immunogenicity of Hantavirus Vaccines against Hemorrhagic Fever with Renal Syndrome

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Abstract

Hemorrhagic fever with renal syndrome (HFRS) is an acute zoonotic disease caused by the orthohantaviruses Puumala, Dobrava-Belgrad (four genotypes), Hantaan (genotype Amur), and Seoul. In the Russian Federation, HFRS occupies the leading place among all natural focal human diseases. Formaldehyde, β-propiolactone, and ultraviolet radiation were tested to select the optimal method for viral inactivation during the development of a whole-virion vaccine against HFRS. The specific activity and the immunogenicity of the vaccine were determined, respectively, by the number of copies of viral RNA per 1 mL and by the neutralizing antibodies in the blood sera of BALB/c mice in response to immunization. Analysis of the immunogenicity of vaccines inactivated with formaldehyde, β-propiolactone, or UV radiation did not find significant differences in the level of induced neutralizing antibodies. At the same time, β-propiolactone has obvious technological advantages as c ompared to formaldehyde and UV radiation: the time of viral inactivation is reduced by dozens of times; neutralization of the inactivator and control of its content in the final vaccine are not required; and the amount of inappropriate protein in the vaccine is decreased due to the decrease in protein aggregation.

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Prospects for the Use of Methylotrophic Yeast in the Creation of Industrial Producers of Feed Enzymes

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In recent years, mycelial fungi have faced competition from recombinant yeast as producers of feed enzymes. An intensive study on genetic diversity identified the yeast genes encoding feed enzymes, the specific activity of which is much higher than that in mycelial fungi. In addition, these genes were expressed in yeast much more efficiently than in mycelial fungi. The use of yeast recombinant producers allowed the expansion of the production of a line of industrial enzymes with a significant reduction in their cost. The advantages of yeast producers of recombinant enzymes include the ability to obtain monoenzymes, which are part of various enzyme complexes used for different purposes. Pichia pastoris methylotrophic yeast is the most attractive subject for the creation of recombinant protein-producing strains.

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Efficiency of Microbial Preparations Based on Bacillus subtilis and Trichoderna harzianum for the Protection of Spring Barley from Diseases in Northwestern Russia

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The efficiency of the microbial preparations Vitaplan LP and Trikhotsin LP, which are based on loose powders of Bacillus subtilis and Trichoderna harzianum cells, respectively, for the protection of spring barley from root rot and helminthosporium leaf spots in the northwest of the Russian Federation has been studied. It was shown that both preparations had a small effect on spring-barley diseases when used for the treatment of seeding material or vegetative plants. The development of helminthosporium-fusarium root rot and helminthosporium leaf spots was reduced by 35%. A higher biological and agricultural effect was achieved with the use of a drug for the treatment of seeds with a low degree of infection by the main root-rot pathogen. Compensation for reduced doses of chemical fungicides with Vitaplan LP had less of an effect than full doses of these fungicides: the effect on root rot and helminthosporium leaf spots was reduced by 17 and 12.7 %, respectively. The use of mixtures of Vitaplan LP with chemical preparations is advisable at a medium degree of seed contamination with root-rot pathogens and a predicted moderate development of helminthosporium leaf spots.

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Glutamyl- and Glutaminyl-tRNA Synthetases Are a Promising Target for the Design of an L-Threonine–Producing Strain

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The present work describes an approach that uses a reduction in biomass accumulation during fermentation to improve the properties of a strain producing L-threonine. Glutamyl- and glutaminyl-tRNA synthetases were chosen as targets. Mutants carrying temperature-sensitive alleles of the mentioned enzymes were obtained. It was shown with this system that suppression of the function of tRNA synthetases led to the rapid arrest of culture growth and an increase in the productivity and conversion of L-threonine synthesis. One of the temperature-sensitive strains was used to obtain mutants with the ts phenotype under nonpermissive conditions. Some of these mutants accumulated less biomass and produced 10–12% more threonine than the original strain.

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Bioaugmentation of Nitrifying Microorganisms to Increase the Efficiency of the Oxidation of Nitrogen Compounds during Wastewater Biofiltration

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The efficiency of the bioaugmentation of nitrifying bacteria into biofilm microbiocenosis with 30 days of continuous biofiltration of a solution of municipal model wastewater has been assessed. The laboratory setup consisted of two parallel operating biofilters. Cultures of ammonium-oxidizing and nitrite-oxidizing bacteria of the Nitrobacter genus were sequentially introduced into one of them after the initial period. It was established that the bioaugmentation of ammonium-oxidizing bacteria into the biofilm microbiocenosis led to an increase in the efficiency of the removal of ammonium nitrogen by an average of 1.6 times as compared to the control biofilter. The subsequent bioaugmentation of nitrite-oxidizing bacteria caused an increase in the amount of nitrates in purified water by an average of two times. The bioaugmentation of nitrifying bacteria in the biofilm microbiocenosis intensified the nitrification process. The quantitative and qualita tive identification of microorganisms via fluorescence in situ hybridization showed an increased number of nitrifying microorganisms in the biofilm of the experimental biofilter and a correlation between this characteristic and the biotransformation of nitrogen compounds, which confirms the efficiency of the introduction of microorganisms into the biofilm.

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Laminin 521 Modulates the Сytotoxic Effect of 5-Fluorouracil on HT29 Colorectal Cancer Cells

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The cytotoxic effect of 5-fluorouracil (5FU) and regorafenib (RF), drugs with different mechanisms of action used to treat colorectal cancer, on an HT29 cell line cultured on plastic or laminin 521 (LM-521) has been studied. It is first shown that LM-521 can increase the sensitivity of tumor cells to 5FU. A possible mechanism of the observed effect of LM-521 on the HT29 cell viability is proposed based on transcriptome and proteome analysis. The interaction of β1-containing integrins on the cell surface with LM-521 can activate the FAK/PI3K/Akt signaling pathways and promote phosphorylation of the YAP transcription coactivator and its binding to the complex with the 14-3-3σ protein. The formation of this complex leads to YAP retention in the cytoplasm and prevents its transport to the nucleus and the activation of antiapoptotic gene transcription.

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Expression of the NADPH + -Dependent Formate-Dehydrogenase Gene from Pseudomona s Increases Lysine Production in Corynebacterium glutamicum

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The psefdh_D221Q gene encodes a mutant formate dehydrogenase from Pseudomonas (P-seFDG_D221Q), which catalyzes formate oxidation with the simultaneous formation of NADPH. It is expressed in cells of lysine-producing Corynebacterium glutamicum strains. The psefdh_D221Q gene was introduced into C. glutamicum strains as part of an autonomous plasmid or was integrated into the chromosome with the simultaneous inactivation of the host formate-dehydrogenase genes. It was shown that the C. glutamicum strains with NADP+-dependent formate dehydrogenase have an increased level of L-lysine synthesis in the presence of formate if their own formate dehydrogenase is inactivated.

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In Vitro System for the Detection of Prostate Cancer Markers via Loop-Mediated Isothermal Amplification

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Loop-mediated isothermal amplification (LAMP) of nucleic acids enables the detection of amplification products 10–20 min after the beginning of the reaction. An intraoperative method for the detection of metastases in lymph nodes based on LAMP, one-step nucleic acid amplification (OSNA), allows the rapid detection of the epithelial-specific marker gene KRT19 in lymph nodes. The standard protocol for OSNA was developed more than 10 years ago to detect breast cancer metastases in lymph nodes. Since then, a new version of the key enzyme involved in the reaction (Bst-polymerase) was obtained, but its use in OSNA has remained unexplored. Moreover, the time has come to apply OSNA to the detection of other cancer types, in particular, prostate cancer. The first step is to create an in vitro system that allows LAMP to be carried out on prostate-cancer cell lines. In this work, the LAMP protocol was developed for the new Bst 3.0 polymerase with optim ized dNTP concentrations and without reverse transcriptase, and cell lines were selected (DU-145 for prostate cancer and Molt-4 for negative control). As a result, a new, in vitro system for the LAMP-based detection of prostate cancer with the marker gene KRT19 was developed.

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