The effect of temperature on bacterial degradation of EDTA in pH-auxostat

The effect of temperature on the maximum specific growth rate and the cell yield was studied during cultivation of two bacterial strains (LPM-4 and Pseudomonas sp. LPM-410) on EDTA under unlimited cell growth conditions in a pH-auxostat. Both strains displayed linear dependence of reciprocal biomass yield against reciprocal specific growth rate, from which the values of rate of substrate expenditure for cell maintenance and the “maximum” yield (i.e., hypothetical yield without cell maintenance processes) were estimated. Analysis of the maximum yield values based on mass–energy balance theory suggested that oxidation of the carboxylic acid side chains of EDTA by a monooxygenase had zero or low energetic efficiency. An Arrhenius equation with different values of Arrhenius parameters within different temperature ranges gave a good fit with the temperature dependence of both growth rate and biomass yield. Specific growth rates of both strains showed a more pronounced temperature dependence than did the cell yields. A possible kinetic mechanism was suggested which might be responsible for the modes of the temperature dependences of specific growth rate and yield that were found. The mechanism is based on a hypothetical key substance governing the metabolic flows, which is formed in a zero-order reaction and destroyed in a first-order reaction, both rate constants depending on temperature according to the Arrhenius law.     

The effect of prolonged intranasal administration of serotonin on the activity of hypothalamic signaling systems in male rats with neonatal diabetes

The functioning of the serotonergic system of the brain is impaired in type II diabetes (T2D), and this leads to metabolic and hormonal dysfunction. The elevation of serotonin level in the CNS is one of the approaches for correcting of the serotonergic system of the brain. The aim of the present work was to investigate the effect of intranasal serotonin (InS) administration for 5 weeks at a daily dose of 20 μg on the metabolic parameters and functional activity of adenylate cyclase signaling system (ACSS) sensitive to peptide hormones and biogenic amines in the hypothalamus of male rats with neonatal T2D. Neonatal model of T2D was induced by injecting streptozotocin (70 mg/kg) into 5-day-old rat pups. Four-month-old animals with apparent T2D manifestations were divided into two groups: an untreated group (D0, n = 6) and a group that received InS treatment (DIS, n = 6). InS administration to diabetic rats restored ACSS regulation by the agonists of type 2 dopamine receptors (DA₂R) and type 4 melanocortin receptors (MC₄R) and enhanced the inhibitory effect of serotonin on adenylate cyclase activity. Elevated expression of genes encoding DA₂R, MC₄R, and serotonin receptor of the 1B subtype (5-HT_1BR) was among the main causes of this change. The relative activity of signaling cascades involving various types of serotonin (G_s-coupled 5-HT_4,6,7R/G_i-coupled 5-HT₁R), dopamine (DA₁R/ DA₂R), and melanocortin (MC₃R/MC₄R) receptors involved in ACSS regulation was also altered in the animals of the DIS group. InS administration restored hormonal regulation in the hypothalamus, improved glucose tolerance, and increased the sensitivity of tissues to insulin. The data obtained show that the elevation of serotonin level in the CNS is a promising approach for the recovery of hypothalamic signaling pathways in T2D and correction of the metabolic disturbances dependent on these pathways.     

Effect of arabinogalactan isolated from Siberian larch on the baking value of soft wheat flour and bread quality

Using additives of arabinogalactan (AG) isolated from Siberian larch, we examined the soft wheat flour quality and quantity of gluten, physical properties of the dough, and quality of finished bread depending on the quantity of the added polysaccharide. In the case of the addition of 1–3% of AG to flour, its content decreases in the final product. An excess amount of AG inhibits yeast growth, which leads to a decrease in bread quality. The optimum addition of AG to flour is 1%, at which the technological properties of flour and dough do not change significantly, but the quality of bread becomes remarkably better; furthermore, arabinogalactan is fully consumed in the course of bread preparation. The use of AG is recommended in the optimum dose for increasing the quality of baked goods.     

Activity of receptor guanylyl cyclases in rats with neonatal streptozotocin diabetes and effect of intranasal administration of insulin and serotonin

In diabetes mellitus (DM) and its complications the functional activity of hormonal signaling systems and their sensitivity to the regulatory action of hormones are changed. We studied the activity of receptor forms of guanylyl cyclase (rGC) sensitive to natriuretic peptides ANP and CNP in the tissues of female rats with 240 day neonatal streptozotocin DM and the effects of intranasal administration of insulin and serotonin (6 weeks, daily dose for rat is 0.48 IU insulin or 20 μg serotonin). In diabetic rats, the increase of the basal rGC activity in the myocardium and its decrease in the uterus and ovaries were found, while in the brain, there were no differences from the control. The treatment of diabetic rats with insulin led to a decrease of the basal rGC activity in the myocardium and its restoration to a normal level in the ovaries. The administration of serotonin produced a less pronounced decrease in the basal enzyme activity in the myocardium compared to insulin and an insignificant increase in the brain. In the myocardium of diabetic rats, the guanylyl cyclase (GC)-stimulating effect of ANP was attenuated, whereas the CNP effect was enhanced; in the ovaries, the GC-stimulating effect of CNP and, to a lesser degree, the effect of ANP were decreased. In the uterus and brain of a diabetic rats, the rGC sensitivity to hormones was practically did not change. The administration of insulin to diabetic rats induces an increase of GC effect of ANP in the myocardium to its values in control and a decrease of CNP effect, as well as partially restored GC effect of CNP in the ovaries under the influence of CNP. The administration of serotonin somewhat enhanced effect of natriuretic peptides in the brain of both control and diabetic animals. Thus, in the neonatal model of type-2 DM in the myocardium and the tissues of the reproductive systems of rats, the functioning of natriuretic peptide-sensitive rGC is changed. The treatment of animals by insulin substantially restores rGC activity, while the intranasal serotonin administration has a little effect.     

Mapping of the quantitative trait loci (QTL) associated with grain quality characteristics of the bread wheat grown under different environmental conditions

The quantitative trait loci (QTL) associated with individual characteristics of grain and flour quality in wheat lines grown under contrasting environmental conditions were mapped. Overall, 22 QTL that manifested under contrasting environmental conditions with various significances were detected on 10 chromosomes. Grain hardness and vitreousness were associated with three loci on chromosomes 5D, 6A, and 3A, while the gluten content, with two loci on chromosomes 5B and 7A. Dough extensibility was associated with only one QTL localized in the region of Glu-A1 locus. One of the loci determining flour and dough strengths is located in the region of Gli-B1 and Glu-B3 loci and the rest, in various regions of chromosomes 1B, 5D, and 4B, where no particular genes associated with grain quality have been yet found. The detected QTL can be used in further experiments on genetic control of gluten formation and quality in wheat.     

Biosynthesis of arachidonic acid by micromycetes (review)

Arachidonic acid (ARA, 5,8,1l,14-cis-eicosatetraenoic acid) is widely used in medicine, pharmaceutics, cosmetics, dietary nutrition, agriculture, and other fields. Microbiological production of ARA is of increased interest since the natural sources (pig liver, adrenal glands, and egg-yolk) cannot satisfy its growing requirements. Mechanisms for ARA biosynthesis as well as the regulation of enzymes involved in this process are considered. Review summarizes literature data concerning individual stages of microbiological ARA production, methods for screening of active strains-producers, physiological regulation of ARA synthesis in micromycetes (the effect of growth phase, medium composition, pH, temperature, and aeration), and effective technologies of fermentation and the product recovery. Information on the whole biotechnological process from strain selection to the ARA yield improvement and purification of the end product is presented.     

Reduction of synthetic ferrihydrite by a binary anaerobic culture of <Emphasis Type="Italic">Anaerobacillus alkalilacustris</Emphasis> and <Emphasis Type="Italic">Geoalkalibacter ferrihydriticus</Emphasis> grown on mannitol at pH 9.5

In the course of an investigation of alkaliphilic iron reduction, metabiotic interactions in a binary culture reducing synthetic ferrihydrite (SF) have been studied. The binary culture contained two anaerobic bacteria: the alkaliphilic organotrophic bacillus Anaerobacillus alkalilacustris, which ferments sugars and sugar alcohols and is incapable of iron reduction, and the dissimilatory iron-reducing bacterium Geoalkalibacter ferrihydriticus, which is able to grow on acetate at the expense of anaerobic respiration. The experiments were performed under conditions of SF excess and deficiency. It was expected that G. ferrihydriticus would oxidize the acetate formed in the course of mannitol fermentation by A. alkalilacustris. The results were different from the expected ones: in the binary culture, fermentation products other than acetate were used for iron reduction; these were primarily formate and ethanol, which led to acetate accumulation rather than consumption. The reduction of SF to magnetite and/or siderite followed the earlier established regularities. The preferential order of donor utilization by G. ferrihydriticus did not conform to the energy yields of the corresponding reactions. Thus, it has been shown that there may be interactions in microbial communities that cannot be predicted from the characteristics of pure cultures. The degradation pathways of organic matter in communities may differ considerably from those observed in pure cultures, even in pure cultures of highly specialized organisms.     

Arachidonic acid production by Mortierella alpina with growth-coupled lipid synthesis

The fungus Mortierella alpina LPM 301, a producer of arachidonic acid (ARA), was found to possess a unique property of a growth-coupled lipid synthesis. An increase in specific growth rate (μ) from 0.03 to 0.05 h⁻¹ resulted in a two-fold increase in the specific rate of lipid synthesis (milligram lipid (gram per lipid-free biomass) per hour). Under batch cultivation in glucose-containing media with urea or potassium nitrate as nitrogen sources, the ARA content was 46.0 and 60.4% of lipid; 16.4 and 18.8% of dry biomass; and 4.2 and 4.5 g l⁻¹, respectively. Under continuous cultivation of the strain, the productivity of ARA synthesis was 16.2 and 19.2 mg l⁻¹ h⁻¹ at μ=0.05 and 0.03 h⁻¹, respectively.     

Effect of intranasal insulin and serotonin on functional activity of the adenylyl cyclase system in myocardium, ovary, and uterus of rats with prolonged neonatal model of diabetes mellitus

The disturbances in hormonal signaling systems, adenylyl cyclase system (ACS) in particular, occur at the early stages of diabetes mellitus (DM) being one of the key causes of its complications. Since the correlation between the severity of DM and severity of disturbances in ACS is established, studying ACS activity can be used for monitoring DM and its complications and evaluating the effectiveness of their treatment. Recently, intranasal insulin (I-I) and the drugs increasing brain serotonin level, thus effectively restoring CNS functions, have begun to be used for the treatment of type 2 DM. However, the mechanisms of their action on peripheral tissues and organs at DM are not understood. The aim of this work was to study an influence of I-I and intranasal serotonin (I-S) on the functional activity of ACS in myocardium, ovary and uterus of rats with a neonatal model of type 2 DM. In the tissues of diabetic rats the changes in the regulation of adenylate cyclase (AC) by guanine nucleotides and hormones acting on enzyme in stimulatory and inhibitory manner were found, and these changes were characterized by receptor and tissue specificity. In diabetic rats I-I restored AC-stimulating effects of isoproterenol in the myocardium, that of guanine nucleotides and gonadotropin in the ovaries and relaxin in the uterus, as well as AC-inhibiting effects of somatostatin in all tissues and norepinephrine in the myocardium. Treatment with I-S led to a partial recovery of AC-inhibiting effect of norepinephrine in the diabetic myocardium, but did not affect the regulation of AC by other hormones. These data indicate that I-I normalizes the functional activity of ACS in the myocardium and in the tissues of reproductive system of female rats with neonatal DM, whereas the effect of I-S on ACS in the studied tissues is less pronounced. These results should be considered for the design and optimization of the strategy of I-I and I-S application for the treatment of DM and its complications.