Effect of oxygen on ethanol fermentation in packed-bed tapered-column reactor

Summary In ethanol production with immobilized yeast a major problem is the provision of nutrients to these highly concentrated cells. O₂ being one of the nutrients of utmost importance to yeast cells, was fed into a column packed with beads with a cell loading of more than 40 g/l. Since addition of large volume of air or O₂ to a cylindrical column reactor would aggravate the problems of pressure build up and channelling caused by the evolving CO₂ gas, a tapered-column reactor and pulsed flow of oxygen gas was used. The supplement of O₂ gas to the tapered column increased the productivity from 21.1 g ethanol x (l gel x h)^-1 to 26.7 g x (l gel x h)^-1, when the ethanol concentration at the outlet was about 80 g/l. The yield coefficient of ethanol was also increased from 0.41 g ethanol/g glucose to 0.43 after O₂ supplement was started. The effects of frequency and duration of O₂ supplement were also determined.     

Mechanism of phosphorus-induced zinc deficiency in cotton. III. Changes in physiological availability of zinc in plants Is mail

The effect of varied supply of P (2.5× 10⁻⁵ to 6× 10⁻⁴ M) and Zn (0 to 10⁻⁶ M) on uptake and concentrations of P and Zn was studied in cotton ( Gossypium hirsutum L. cv. Deltapine 15/21) grown in nutrient solution under controlled environmental conditions. At a given Zn supply, increasing levels of P had no significant effect on the concentrations of total Zn in plants. However, increasing levels of P induced or enhanced visual Zn deficiency symptoms when the Zn concentration in the nutrient solution was low. The concentrations of water-soluble Zn in roots and shoots constituted 60% of the total Zn concentrations for plants grown with low P and 30% for plants grown with high P. The concentration of water-soluble Zn in leaves, but not total Zn, was closely correlated with visual Zn deficiency symptoms, levels of chlorophyll, super oxide dismutase and membrane permeability. The critical deficiency concentration of water-soluble Zn in cotton leaves was in the range of 6 to 7 μg (g dry weight)⁻¹ or about 1.0 μg (g fresh weight)⁻¹. The results show that high P concentrations in plant tissue decrease the physiological availability of Zn. Water-soluble Zn in the tissue appears to be a suitable indicator for Zn nutritional status in general and phosphorus-induced Zn deficiency in particular. Also in field-grown orange trees (Citrus sinensis) visual Zn deficiency symptoms in leaves were closely related to the concentration of water-soluble Zn.     

Variation in phosphorus and sulfur content shapes the genetic architecture and phenotypic associations within the wheat grain ionome

Dissection of the genetic basis of wheat ionome is crucial for understanding the physiological and biochemical processes underlying mineral accumulation in seeds, as well as for efficient crop breeding. Most of the elements essential for plants are metals stored in seeds as chelate complexes with phytic acid or sulfur‐containing compounds. We assume that the involvement of phosphorus and sulfur in metal chelation is the reason for strong phenotypic correlations within ionome. Adjustment of element concentrations for the effect of variation in phosphorus and sulfur seed content resulted in drastic change of phenotypic correlations between the elements. The genetic architecture of wheat grain ionome was characterized by quantitative trait loci (QTL) analysis using a cross between durum and wild emmer wheat. QTL analysis of the adjusted traits and two‐trait analysis of the initial traits paired with either P or S considerably improved QTL detection power and accuracy, resulting in the identification of 105 QTLs and 617 QTL effects for 11 elements. Candidate gene search revealed some potential functional associations between QTLs and corresponding genes within their intervals. Thus, we have shown that accounting for variation in P and S is crucial for understanding of the physiological and genetic regulation of mineral composition of wheat grain ionome and can be implemented for other plants.     

Population genetic structure of turbot (Scophthalmus maximus L., 1758) in the Black Sea

Turbot, Scophthalmus maximus, is a commercially important demersal flatfish species distributed throughout the Black Sea. Several studies performed locally with a limited number of specimens using both mitochondrial DNA (mtDNA) and microsatellite markers evidenced notable genetic variation among populations. However, comprehensive population genetic studies are required to help management of the species in the Black Sea. In the present study eight microsatellite loci were used to resolve the population structure of 414 turbot samples collected from 12 sites across the Black Sea. Moreover, two mtDNA genes, COI and Cyt-b, were used for taxonomic identification. Microsatellite markers of Smax-04 and B12-I GT14 were excluded from analysis due to scoring issues. Data analysis was performed with the remaining six loci. Loci were highly polymorphic (average of 17.8 alleles per locus), indicating high genetic variability. Locus 3/20CA17, with high null allele frequency (>30%), significantly deviated from HW equilibrium. Pairwise comparison of the F_ST index showed significant differences between most of the surveyed sampling sites (P < 0.01). Cluster analysis evidenced the presence of three genetic groups among sampling sites. Significant genetic differentiation between Northern (Sea of Azov and Crimea) and Southern (Turkish Black Sea Coast) Black Sea sampling sites were detected. The Mantel test supported an isolation by distance model of population structure. These findings are vital for long-term sustainable management of the species and development of conservation programs. Moreover, generated mtDNA sequences would be useful for the establishment of a database for S. maximus.     

Adequate magnesium nutrition mitigates adverse effects of heat stress on maize and wheat

Aims

Heat stress is a growing concern in crop production because of global warming. In many cropping systems heat stress often occurs simultaneously with other environmental stress factors such as mineral nutrient deficiencies. This study aimed to investigate the role of adequate magnesium (Mg) nutrition in mitigating the detrimental effects of heat stress on wheat (Triticum aestivum) and maize (Zea mays).

Methods

Wheat and maize plants were grown in solution culture with low or adequate Mg supply at 25/22 °C (light/dark). Half of the plants were, then, exposed to heat stress at 35/28 °C (light/dark). Development of leaf chlorosis and changes in root and shoot growth, chlorophyll and Mg concentrations as well as the activities of major antioxidative enzymes were quantified in the experimental plants. Additionally, maize plants were analyzed for the specific weights (e.g., dry or fresh weight per a given leaf surface area) and soluble carbohydrate concentrations of sink and source leaves.

Results

Visual leaf symptoms of Mg deficiency were aggravated in wheat and maize when exposed to heat stress. In both species, root growth was more sensitive to Mg deficiency than shoot growth, and the shoot-to-root ratios peaked when heat stress was combined with Mg deficiency. Magnesium deficiency markedly reduced soluble carbohydrate concentrations in young leaf; but resulted in substantial increase in source leaves. Magnesium deficiency also increased activities of antioxidative enzymes, especially when combined with heat stress. The highest activities of superoxide dismutase (up to 80 % above the control), glutathione reductase (up to 250 % above the control) and ascorbate peroxidase (up to 300 % above the control) were measured when Mg-deficient plants were subjected to heat, indicating stimulated formation of reactive oxygen species (ROS) in Mg deficient leaves under heat stress.

Conclusions

Magnesium deficiency increases susceptibility of wheat and maize plants to heat stress, probably by increasing oxidative cellular damage caused by ROS. Ensuring a sufficiently high Mg supply for crop plants through Mg fertilization is a critical factor for minimizing heat-related losses in crop production.     

Determining immunoassay cutoff value using Western blot results to predict hepatitis C infection in blood donors with low-titer anti-HCV reactivity

Since the 1990s, blood donors have been scanned for anti-hepatitis C virus (anti-HCV) antibodies, which can be defined by enzyme immunoassay as a screening test. In this population, false-reactive ratios have been high. Recently, some authors have aimed to find a cutoff value for anti-HCV different from those established by test manufacturers to predict HCV infection. In this study, 321 patients, after two repeating tests, had reactive results in s/co <10 titers on anti-HCV test. The patients were 29.6 % (n?=?95) in women and 70.4 % (n?=?226) in men. The patients were classified into three groups by Western blot (WB) results (PS, positive; NG, negative; and ID, indeterminate). The average anti-HCV titer of the whole group was 2.61?±?1.96. Anti-HCV titers of subgroups were 2.43?±?1.95 in NG, 4.93?±?2.53 in PS, and 2.50?±?1.65 in ID (p?<?0.001). There was a significant difference between NG and PS and between PS and ID subgroups (p?<?0.001). There was a positive correlation between WB and anti-HCV titers in all patients (r?=?0.298, p?<?0.001), in women (r?=?0.282, p?<?0.001), and in men (r?=?0.337, p?=?0.002). According to receiver operator characteristic curve analysis, the cutoff value of anti-HCV titer to predict hepatitis C infection was >2.61 s/co, with 74.1 % sensitivity and 71.6 % specificity (area under the curve, 0.820; 95 % confidence interval, 0.753 to 0.887). We suggest that an effective cutoff value for anti-HCV other than that established by the manufacturer cannot be assigned to predict hepatitis C infection for blood donors in low-prevalence areas.     

Cell surface receptors for signal transduction and ligand transport: a design principles study

Receptors constitute the interface of cells to their external environment. These molecules bind specific ligands involved in multiple processes, such as signal transduction and nutrient transport. Although a variety of cell surface receptors undergo endocytosis, the systems-level design principles that govern the evolution of receptor trafficking dynamics are far from fully understood. We have constructed a generalized mathematical model of receptor–ligand binding and internalization to understand how receptor internalization dynamics encodes receptor function and regulation. A given signaling or transport receptor system represents a particular implementation of this module with a specific set of kinetic parameters. Parametric analysis of the response of receptor systems to ligand inputs reveals that receptor systems can be characterized as being: i) avidity-controlled where the response control depends primarily on the extracellular ligand capture efficiency, ii) consumption-controlled where the ability to internalize surface-bound ligand is the primary control parameter, and iii) dual-sensitivity where both the avidity and consumption parameters are important. We show that the transferrin and low-density lipoprotein receptors are avidity-controlled, the vitellogenin receptor is consumption-controlled, and the epidermal growth factor receptor is a dual-sensitivity receptor. Significantly, we show that ligand-induced endocytosis is a mechanism to enhance the accuracy of signaling receptors rather than merely serving to attenuate signaling. Our analysis reveals that the location of a receptor system in the avidity-consumption parameter space can be used to understand both its function and its regulation.     

A model in environmental training--The University / Elementary School / Municipality Cooperation

This study targets development of an effective training scheme model that can be implemented at elementary school level with focus on recovery and recycling of wasted papers in Turkey. For this purpose, three schools were chosen from a district within Istanbul. They were separated from one another as full intervention (FI), semi-intervention (SI) and control (C) schools. Different levels of educational activities carried out in the schools, mostly in the FI school, were directed toward being informative as regards recycling and the development of a positive attitude. Afterwards, in order to evaluate the effects of the training, paper wastes were collected in recycle bins placed at appropriate points in schools and weighed on a weekly basis. Quite a significant result was found (p = 0.0001), when the difference was calculated through the Kruskal Wallis Variance Analysis method, regarding the weekly average amount of paper in each of the three schools against per person. Furthermore, when the results were evaluated and compared as to the ones before the 2.5 months summer vacation and the ones after it, the seven measurements taken before (p = 0.001) and the eight taken afterwards (p = 0.0001), were found to have valid differences, once again, as against schools. The results show that the approach we provided to education is an effective method not only for the collection of paper wastes but also for applications in various areas of health education.     

Oxidant-induced DNA damage by quartz in alveolar epithelial cells

Respirable quartz has recently been classified as a human carcinogen. Although, studies with quartz using naked DNA as a target suggest that formation of oxyradicals by particles may play a role in the DNA-damaging properties of quartz, it is not known whether this pathway is important for DNA damage in the target cells for quartz carcinogenesis, i.e. alveolar epithelial cells. Therefore, we determined in vitro DNA damage by DQ12 quartz particles in rat and human and alveolar epithelial cells (RLE, A549) using the single cell gel electrophoresis/comet assay. The radical generation capacity of quartz was analysed by electron spin resonance (ESR) and by immunocytochemical analysis of the hydroxyl radical-specific DNA lesion 8-hydroxydeoxyguanosine (8-OHdG) in the epithelial cells. Quartz particles as well as the positive control hydrogen peroxide, caused a dose-dependent increase in DNA strand breaks in both cell lines. DNA damage by quartz was significantly reduced in the presence of the hydroxyl-radical scavengers mannitol or DMSO. The involvement of hydroxyl radicals was further established by ESR measurements and was also demonstrated by the ability of the quartz to induce formation of 8-OHdG. In conclusion, our data show that quartz elicits DNA damage in rat and human alveolar epithelial cells and indicate that these effects are driven by hydroxyl radical-generating properties of the particles.     

Radiotherapy: effects on expanded skin

Although the combination of radiation and tissue expansion has been associated with a significant rate of complications, the specific pathophysiology has yet to be clearly elucidated. The objective of this study was to develop a model to identify and examine specific histologic changes associated with tissue expansion and irradiation. Rectangular 50-cc silicone tissue expanders were placed subcutaneously over the midline dorsum of 18 adult New Zealand white rabbits. Preoperative radiographic dosimetry demonstrated that the radiation portal was away from vital intraabdominal structures. The expanders were inflated with 10 cc of saline every other day for a total of 80 cc. Expanders were left in place for 2 to 3 weeks to allow fibrovascular capsule formation. The rabbits were then divided into three groups (six rabbits per group), each receiving one of three nonfractionated doses of radiation (20, 25, or 35 Gy). Half of the expanded skin was irradiated using a single dose, and the other half served as a nonirradiated control. Capsules and skin were harvested 6 weeks after the delivery of radiation, allowing the beginning of chronic radiation changes to occur. Using hematoxylin and eosin staining, histomorphometric analysis was performed. The data were analyzed using Student's test. Although irradiation did not affect dermal thickness, it did cause a statistically significant increase in epidermal thickness. At 20, 25, and 35 Gy the increase in epidermal thickness was 43, 90, and 130 percent, respectively. Although significant epidermal changes could be identified, capsular and dermal alterations were not evident. Further studies evaluating the long-term effects of alterations in capsular formation caused by radiation may be required.