D-gluconic Acid Research Articles

Immobilized glucose oxidase on magnetic silica and alumina: Beyond magnetic separation

Here we report immobilization of glucose oxidase (GOx) on magnetic silica (Fe3O4-SiO2) and alumina (Fe3O4-Al2O3) functionalized with amino groups using glutaraldehyde as a linker. Magnetic support based biocatalysts demonstrate high catalytic activity in d-glucose oxidation to D-gluconic acid at pH 5–7.5 and temperature of 30–50 °C with the best activities of 95% and 91% for magnetic silica and alumina, respectively. A comparison of magnetic and non-magnetic alumina and silica shows a significant enhancement of the relative catalytic activity for magnetic supports, while the silica based biocatalysts show a higher activity than the biocatalysts based on alumina. A noticeably higher activity of GOx immobilized on magnetic supports is explained by synergy of the GOx inherent activity and enzyme-like activity of iron oxide nanoparticles, while the enhancement with silica based catalysts is most likely due to a larger pore size and stronger Brønsted acid sites. Excellent relative activity of Fe3O4-SiO2-GOx (95% of native GOx) in a tolerant pH and temperature range as well as high stability in a repeated use (6% relative activity loss after five catalytic cycles) makes this catalyst promising for practical applications.

Alginate/Hydroxyapatite-Based Nanocomposite Scaffolds for Bone Tissue Engineering Improve Dental Pulp Biomineralization and Differentiation.

Tissue engineering is widely recognized as a promising approach for bone repair and reconstruction. Several attempts have been made to achieve materials that must be compatible, osteoconductive, and osteointegrative and have mechanical strength to provide a structural support. Composite scaffolds consisting in biodegradable natural polymers are very promising constructs. Hydroxyapatite (HAp) can support alginate as inorganic reinforcement and osteoconductive component of alginate/HAp composite scaffolds. Therefore, HAp-strengthened polymer biocomposites offer a solid system to engineer synthetic bone substitutes. In the present work, HAp was incorporated into an alginate solution and internal gelling was induced by addition of slowly acid-hydrolyzing D-gluconic acid delta-lactone for the direct release of calcium ions from HAp. It has been previously demonstrated that alginate-based composites efficiently support adhesion of cancer bone cell lines. Human dental pulp stem cells (DPSCs) identified in human dental pulp are clonogenic cells capable of differentiating in multiple lineage. Thus, this study is aimed at verifying the mineralization and differentiation potential of human DPSCs seeded onto scaffolds based on alginate and nano-hydroxyapatite. For this purpose, gene expression profile of early and late mineralization-related markers, extracellular matrix components, viability parameters, and oxidative stress occurrence were evaluated and analyzed. In summary, our data show that DPSCs express osteogenic differentiation-related markers and promote calcium deposition and biomineralization when growing onto Alg/HAp scaffolds. These findings confirm the use of Alg/HAp scaffolds as feasible composite materials in tissue engineering, being capable of promoting a specific and successful tissue regeneration as well as mineralized matrix deposition and sustaining natural bone regeneration.

Synthetic CaO-based sorbent for high-temperature CO2 capture in sorption-enhanced hydrogen production

Calcium precursor and surfactant addition on properties of synthetic alumina-containing CaO-based for CO2 capture and for sorption-enhanced steam methane reforming process (SE-SMR) were investigated. Results showed that the sorbent derived from calcium d-gluconic acid (CG-AN) offered CO2 sorption capacity of 0.38 g CO2/g sorbent, which is greater than 0.17 g CO2/g sorbent of the sorbent derived from calcium nitrate (CN-AN). Addition of CTAB surfactant during synthesis was found to enhance CO2 sorption capacity for CG-AN but not for CN-AN sorbents. Stability tests of the modified sorbents for 10 cycles showed that CG-AN-CTAB provided higher CO2 sorption capacity than CN-AN-CTAB for each corresponding cycle. Incorporation of CG-AN with Ni catalyst (Ni-CG-AN) using wet-mixing technique offered the longest pre-breakthrough period of 60 min for average maximum H2 purity of 88% at 600 °C and a steam/methane molar ratio of 3.

The acidity and self-catalyzed lactonization of l-gulonic acid: Thermodynamic, kinetic and computational study

Lactonization and proton dissociation of sugar acids take place simultaneously in acidic aqueous solutions. The protonation-deprotonation processes are always fast, whilst the formation and hydrolysis of γ- and δ-lactones are usually slower. Thus, both thermodynamic and kinetic information are required for the complete understanding of these reactions. The protonation constant (Kp) of l-gulonate (Gul–) was determined from potentiometric and polarimetric measurements, while the individual lactonization constants (KL,γ and KL,δ) for l-gulonic acid (HGul) were obtained via13C NMR experiments. The applicability of this method was proven by measuring these well-known constants for d-gluconic acid (HGluc) and by comparing them to literature data. l-gulonic acid γ-lactone (γ-HGul) has remarkable stability in contrast with δ-HGul as well as γ- and δ-HGluc. The polarimetric measurement implies that the main factor responsible for the enhanced stability of γ-HGul is that its hydrolysis is much slower than that of δ-HGul. This higher stability of the γ-HGul ring over its δ-isomer was also confirmed by quantum chemical calculations. A new confirmed feature of the reaction is that in parallel to H3O+, HGul also catalyzes the formation and reverse hydrolytic processes of γ-HGul, similarly to other general acid catalysts.

Insights into Sustainable Glucose Oxidation Using Magnetically Recoverable Biocatalysts

Here, we developed magnetically recoverable biocatalysts for enzymatic oxidation of d-glucose to d-gluconic acid with high product yields. The catalyst support is based on nanoparticle clusters (NPCs) composed of magnetite particles and coated with the amino terminated silica layer to facilitate further functionalization. It involves the attachment of the glutaraldehyde linker followed by the covalent attachment of glucose oxidase (GOx) via its amino groups. It was established that the NPCs with a diameter of ∼430 nm attach 33% more GOx molecules than NPCs with a diameter of ∼285 nm, although the surface area of the former is lower than that of the latter. At the same time, the biocatalyst based on the smaller NPCs shows higher relative activity of 94% than that (87%) of the biocatalyst based on the larger NPCs, both at 50 °C and pH 7 (optimal reaction conditions). This surprising result has been explained by a combination of two major factors such as GOx crowding on the support surface which should preve...

The functions of yhcZ gene during Bacillus thuringiensis growth

yhcZ and yhcY genes constitute a two-component system in Bacillus subtilis and B. cereus that regulates bacterial growth. However, the exact biological function of yhcZ gene in B. thuringiensis has not been fully elucidated. In this study, we proved that HD73_5824 is an yhcZ gene in B. thuringiensis subsp. kurstaki HD73 strain by combining gene functional annotation, analysis of upstream and downstream genes arrangement, and amino acid sequence alignment. This yhcZ gene may co-regulate bacterial growth with HD73_5825 gene (yhcY gene) by constituting a two-component system. Homologous recombination technology was employed to knock out yhcZ gene of HD73, resulting in a mutant strain HD (ΔyhcZ). The HD (ΔyhcZ) strain grew slower than wild-type strain HD73 in both LB and SSM medium. Re-introduction of yhcZ gene in HD (ΔyhcZ) strain can partially restore the growth, indicating that the deletion of yhcZ gene impacts the cell growth of HD73 strain. HD (ΔyhcZ) strain grew faster than HD73 strain in M9 medium with 0.4% glucose as the sole carbon source, implying that the yhcZ gene plays an important role in glucose utilization by HD73 strain. The results of biolog assay showed that HD (ΔyhcZ) exhibits a lower average well color development compared to HD73. HD(ΔyhcZ) cells also demonstrated a decreased capacity for absorbing and utilizing D/L-serine, formic acid, D-gluconic acid, L-histamine, D-methyl lactate, and citric acid, indicating that yhcZ gene could dramatically influence carbon source utilization of HD73 strains. Additionally, HD (ΔyhcZ) was less resistant to 8% NaCl, suggesting that yhcZ gene may be involved in the expression and regulation of genes related to high-salt stress response in bacterial cells. The results above show that the yhcZ gene significantly promotes glucose and other carbon sources utilization of HD73 strain during growth. Our findings will lay a foundation not only for analyzing the regulatory mechanisms of glucose and carbon sources utilization by yhcZ gene, but also providing a reference for the further research on bacterial growth and fermentation.

Effect of growing glycosylation extents on the self-assembly and active targeting in vitro of branched poly(ethylene oxide)-poly(propylene oxide) block copolymers

In this work, we investigated for the first time the effect of the gradual increase of the glycosylation extent on self-assembly of a highly hydrophilic four-arm poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymer, Tetronic® 1107. After the initial characterization that confirmed the chemical modification, the effect of the glycosylation extent on the critical micellar concentration (CMC) was characterized by dynamic light scattering. Conjugation of a d-gluconic acid (the oxidized form of d-glucose) in each terminal block resulted in a dramatic decrease of the CMC by 8- to 11-fold. In contrast, further glycosylation with lactobionic acid (an oxidized form of lactose) and gluconic acid+lactobionic acid had a detrimental effect due to the increase of the amphiphile hydrophilicity. Then, glycosylated PMs successfully encapsulated the tyrosine kinase inhibitor imatinib, increasing its aqueous solubility by up to 100 times. Glycosylated polymeric micelles showed very good cell compatibility in the Rh30 cell line. These cells are a model of rhabdomyosarcoma, a tumor that overexpresses glucose transporter-1 that is targeted by the sugar residues. Finally, we compared the cytotoxicity of free and nanoencpasulated imatinib to inhibit the proliferation a in which tyrosine kinase signaling promotes growth and glucose transporter-1 (GLUT-1; for which glucose is the main substrate) is overexpressed. Nano-encapsulation reduced the inhibitory concentration 50 (IC50) from 27.80±3.70μM for the free drug to 0.33±0.01μM for the PMs modified with gluconic acid, representing an 84-fold increase in the anti-cancer efficacy in vitro. Overall results highlight the potential of tuned glycosylation to increased the micellization trend of these amphiphiles and, at the same time, increase accumulation in cells that overexpress sugar receptors.

Biochemical Measurement of Glycogen: Method to Investigate the AMPK-Glycogen Relationship.

Glycogen is a main carbohydrate energy storage primarily found in fungi and animals. It is a glucose polymer that comprises α(1-4) glycosidic linkages attaching UDP-glucose molecules linearly and α(1-6) linkages branching glucose chains every 8-10 molecules to the main backbone chain. Glycogen synthase, branching enzyme, and glycogen phosphorylase are key enzymes involved in glycogen synthesis and degradation. These enzymes are tightly regulated by upstream kinases and phosphatases that respond to hormonal cues in order to coordinate storage and degradation and meet the cellular and organismal metabolic needs. The 5'AMP-activated protein kinase (AMPK) is one of the main regulators of glycogen metabolism. Despite extensive research, the role of AMPK in glycogen synthesis and degradation remains controversial. Specifically, the level and duration of AMPK activity highly influence the outcome on glycogen reserves. Here, we describe a rapid and robust protocol to efficiently measure the levels of glycogen in vitro. We use the commercially available glycogen determination kit to hydrolyze glycogen into glucose, which is oxidized to form D-gluconic acid and hydrogen peroxide that react with the OxiRed/Amplex Red probe generating a product that could be detected either in a colorimetric or fluorimetric plate format. This method is quantitative and could be used to address the role of AMPK in glycogen metabolism in cells and tissues. Summary This chapter provides a quick and reliable biochemical quantitative method to measure glycogen in cells and tissues. Briefly, this method is based on the degradation of glycogen to glucose, which is then specifically oxidized to generate a product that reacts with the OxiRed probe with maximum absorbance at 570nm. This method is very accurate and highly sensitive. In the notes of this chapter, we shed the light on important actions that should be followed to get reliable results. We also state advantages and disadvantages of this method in comparison to other glycogen measurement techniques.

Whole-cell biotransformation for simultaneous synthesis of L-2-aminobutyric acid and D-gluconic acid in recombinant Escherichia coli

A whole-cell catalyst using Escherichia coli BL21(DE3) as a host, expressing L- threonine dehydratase from Escherichia coli, and co-expressing leucine dehydrogenase from Bacillus cereus and glucose dehydrogenase from Bacillus subtilis for cofactor regeneration, was constructed and used for one-pot production of L-2-aminobutyric acid (L-ABA) and D- gluconic acid from L-threonine and D-glucose. We used shake-flask culture to study the whole-cell catalytic condition including temperature, pH, proper permeabilization of cells and optimal wet cells amount. Moreover, the whole-cell catalyst was cultured in 5-L fermentor by fed-batch fermentation, and 164 g/L L-threonine and 248 g/L D-glucose were converted to 141.6 g/L L-ABA and 269.4 g/L D-gluconic acid. The whole-cell catalyst is promising to fulfill industrial requirements for L-ABA and D-gluconic acid.

Promising Strain of Acinetobacter from Soil for Utilization of Gluconic Acid Production

Gluconic acid, a food additive, is used in many foods to control acidity or binds metals such as calcium, iron. Acinetobacter sp. WR326, newly isolated from soil possesses high phosphate solubilizing activity and do not require pyrroloquinoline quinone (PQQ) for glucose dehydrogenase (GDH) activity. In this study the gluconic acid production potential of these bacteria was investigated. Firstly, Acinobacter sp. WR326 was incubated in tricalcium phosphate medium (TCP) with varying glucose concentrations (100, 250, 500 mM), at a temperature of 30 °C for 5 days (120 hours). The highest gluconic acid yield (59%) was observed at a glucose concentration of 100 mM. Then three different levels of gluconic acid addition to the medium (50, 100, 200 mM) were tested. When Acinetobacter sp. WR326 strain was cultivated with a 100 mM glucose and 100 mM gluconic acid the yield increased to 95.27 %. In any trials 2 -keto D-gluconic acid was not detected in the medium. As a conclusion, Acinetobacter sp. WR326 may be considered novel potential bacterial strain for gluconic acid production.

The effect of ambient pH modulation on ochratoxin A accumulation byAspergillus carbonarius

Aspergillus carbonarius, the main cause of severe post-harvest decay of vine fruit, is considered the major source of ochratoxin A (OTA) contamination of grapes and derived products. The factors inducing OTA accumulation byA. carbonarius and its contribution to pathogenicity remain unclear. Present findings indicate that the production of organic acids, such as D-gluconic acid (GLA) and citric acid, byA. carbonarius in the growth medium or in the decayed fruit tissue was directly related to ambient pH reduction. Under these conditions, induced transcript expression of genes involved in OTA biosynthesis occurred concurrently with mycotoxin accumulation. The high accumulation of OTA during acidification process raised the question of its importance in host-pathogen interactions during the fungal colonisation. Treatment of colonised grapes with sodium bicarbonate reduced accumulation of organic acid and OTA with a concomitant reduction in decay development, suggesting that tissue acidification is a significant factor inA. carbonarius pathogenicity. The present findings suggest that ambient pH is a regulatory signal for induction of mycotoxin production byA. carbonarius under the dynamic nutritional growth conditions occurring in culture. Yet the molecular mechanisms of OTA biosynthesis induction during colonisation of the acidic host environment are still unclear and should be further investigated.

Total Synthesis of Lagerstannin C: Follow-up of the Khanbabaee’s Synthesis

This report describes the total synthesis of lagerstannin C, a natural ellagitannin that has d-gluconic acid in the molecule. The study presented here is the first synthesis of the gluconic acid containing ellagitannin. The key step in the synthesis is the opening of δ-lactone through transesterification to form the corresponding benzyl ester.

Correction for Wertz et al., "Genomic and Physiological Characterization of the Verrucomicrobia Isolate Geminisphaera colitermitum gen. nov., sp. nov., Reveals Microaerophily and Nitrogen Fixation Genes".

Author(s): Wertz, John T; Kim, Eunji; Breznak, John A; Schmidt, Thomas M; Rodrigues, Jorge LM | Abstract: Description of Didymococcus gen. nov. Didymococcus gen. nov. (Di.dy.mo.coc'cus. Gr. fem. n. didymos pair; N.L. masc. n. coccus (from Gr. masc. n. kokkos, grain, seed), coccus; N.L. masc. n. Didymococcus a coccus in pairs). Description of Didymococcus colitermitum sp. nov. Didymococcus colitermitum sp. nov. (co.li.ter'mi.tum. L. n. colon, colon, part of the large intestine; L. n. termes -itis, wood-eating worm, termite; N.L. gen. pl. n. colitermitum, of the gut of termites). Cells are coccoid (0.25 μm to 0.5 μm in diameter) and occur almost exclusively in pairs, with a Gram-negative cell wall morphology that includes an outer membrane. Cells are nonmotile, obligate aerobes and are microaerophilic. The shortest generation times occur in liquid medium under an atmosphere of 2 to 8% O2 (balance N2). On solid R2A medium, colonies are 2 to 4 mm in diameter, have an entire margin and a low convex, mucoid morphology, and are cream colored. Cells do not possess catalase or NADH/ NADPH peroxidase activity. Nitrogenase activity is inferred through growth on nitrogen-free medium. Growth occurs in liquid media between 15 and 35°C (optimum, 30°C); there is no growth at 37°C or 4°C. Growth occurs at a pH range of 5.5 to 7.5 (optimum, 7.0); there is no growth at a pH of ≤5 or ≥8. Substrates utilized as energy sources include starch, D-cellobiose, D-maltose, D-glucose, D-galactose, and one or more components present in yeast extract. Microcrystalline cellulose, methylcellulose, carboxy methylcellulose, xylan, D-fructose, D-mannose, D-trehalose, sucrose, D-ribose, D-xylose, L-arabinose, D-mannitol, D-sorbitol, D-raffinose, DL-lactate, sodium pyruvate, sodium fumarate, sodium acetate, allantoin, D-glucuronate, D-galacturonate, D-gluconic acid, xanthine, tannic acid, resourcinol, vanillic acid, sodium benzoate, and trimethylbenzoate are not utilized. The genome of type strain TAV2 is 5.2 Mb in size, contains 60.5 mol% G+C, and possesses one 16S rRNA gene copy. The type strain, isolated from guts of Reticulitermes flavipes (Kollar) collected in Dansville, MI, is TAV2 (ATCC BAA-2264; DSM 25453).

Ester hydrolysis: Conditions for acid autocatalysis and a kinetic switch

Autocatalysis can be used to obtain a sharp switch in state after a programmable time lag. Here, autocatalysis driven by acid concentration during the dissolution and hydrolysis of solid esters was investigated. In a generic model of the process, conditions were identified for observation of a kinetic switch with the introduction of an inhibitor species, bicarbonate, to delay the onset of autocatalysis. The kinetic profiles from the hydrolysis of two esters, d-gluconic acid δ-lactone and dl-lactide, were examined and evidence for dissolution-limited acid autocatalysis was obtained with lactide.

Carbohydrate uptake in Advenella mimigardefordensis strain DPN7T is mediated by periplasmic sugar oxidation and a TRAP-transport system.

In this study, we investigated an SBP (DctPAm ) of a tripartite ATP-independent periplasmic transport system (TRAP) in Advenella mimigardefordensis strain DPN7T . Deletion of dctPAm as well as of the two transmembrane compounds of the tripartite transporter, dctQ and dctM, impaired growth of A. mimigardefordensis strain DPN7T , if cultivated on mineral salt medium supplemented with d-glucose, d-galactose, l-arabinose, d-fucose, d-xylose or d-gluconic acid, respectively. The wild type phenotype was restored during complementation studies of A. mimigardefordensis ΔdctPAm using the broad host vector pBBR1MCS-5::dctPAm . Furthermore, an uptake assay with radiolabeled [14 C(U)]-d-glucose clearly showed that the deletion of dctPAm , dctQ and dctM, respectively, disabled the uptake of this aldoses in cells of either mutant strain. Determination of KD performing thermal shift assays showed a shift in the melting temperature of DctPAm in the presence of d-gluconic acid (KD 11.76 ± 1.3 µM) and the corresponding aldonic acids to the above-mentioned carbohydrates d-galactonate (KD 10.72 ± 1.4 µM), d-fuconic acid (KD 13.50 ± 1.6 µM) and d-xylonic acid (KD 8.44 ± 1.0 µM). The sugar (glucose) dehydrogenase activity (E.C.1.1.5.2) in the membrane fraction was shown for all relevant sugars, proving oxidation of the molecules in the periplasm, prior to transport.

An aldonolactonase AltA from Penicillium oxalicum mitigates the inhibition of β-glucosidase during lignocellulose biodegradation.

Efficient deconstruction of lignocellulose is achieved by the synergistic action of various hydrolytic and oxidative enzymes. However, the aldonolactones generated by oxidative enzymes have inhibitory effects on some cellulolytic enzymes. In this work, D-glucono-1,5-lactone was shown to have a much stronger inhibitory effect than D-glucose and D-gluconate on β-glucosidase, a vital enzyme during cellulose degradation. AltA, a secreted enzyme from Penicillium oxalicum, was identified as an aldonolactonase which can catalyze the hydrolysis of D-glucono-1,5-lactone to D-gluconic acid. In the course of lignocellulose saccharification conducted by cellulases from P. oxalicum or Trichoderma reesei, supplementation of AltA was able to relieve the decrease of β-glucosidase activity obviously with a stimulation of glucose yield. This boosting effect disappeared when sodium azide and ethylenediaminetetraacetic acid (EDTA) were added to the saccharification system to inhibit the activities of oxidative enzymes. In summary, we describe the first heterologous expression of a fungal secreted aldonolactonase and its application as an efficient supplement of cellulolytic enzyme system for lignocellulose biodegradation.

A study of biocatalysts based on glucose oxidase.

During this work, we studied the possibility of glucose oxidase (GOx) covalent immobilization on a modified inorganic support. A series of GOx-based biocatalysts was synthesized by crosslinking the enzyme to a surface of modified silica or alumina. Polyelectrolyte layers were used as modifiers for the silica and alumina surfaces. These layers promote tight binding of the GOx to the support. The biocatalyst's activity and stability were studied using an oxidation reaction of d-glucose to d-gluconic acid. It was found that GOx immobilized on the modified SiO2 using glutardialdehyde as a crosslinking agent was the most active and stable catalytic system, showing an 85% yield of gluconic acid. A study of the synthesized biocatalyst structure using FTIR spectroscopy showed that the enzyme was covalently crosslinked to the surface of an inorganic support modified with chitosan and glutardialdehyde. In the case of SiO2, the quantity of the immobilized enzyme was higher than in the case of Al2O3.

Gold Nanoparticle-Decorated Diatom Biosilica: A Favorable Catalyst for the Oxidation of d-Glucose.

Diatoms are unicellular algae of enormous biodiversity that occur in all water habitats on earth. Their cell walls are composed of amorphous biosilica and exhibit species-specific nanoporous to microporous and macroporous patterning. Therefore, diatom biosilica is a promising renewable material for various applications, such as in catalysis, drug-delivery systems, and biophotonics. In this study, diatom biosilica of three different species (Stephanopyxis turris, Eucampia zodiacus, and Thalassiosira pseudonana) was used as support material for gold nanoparticles using a covalent coupling method. The resulting catalysts were applied for the oxidation of d-glucose to d-gluconic acid. Because of its high specific surface area, well-established transport pores, and the presence of small, homogeneously distributed gold nanoparticles on the surface, diatom biosilica provides a highly catalytically active surface and advanced accessibility to the active sites. In comparison to those of the used reference supports, higher catalytic activities (up to 3.28 × 10–4 mmolGlc s–1 mgAu–1 for T. pseudonana biosilica) and slower deactivation were observed for two of the diatom biosilica materials. In addition, diatom biosilica showed very high gold-loading capacities (up to 45 wt %), with a homogeneous nanoparticle distribution.

Qualitative Assessment of the White Wine Varieties Grown in Dealu Bujorului Vineyard, Romania

Ecoclimatic conditions have a great influence on grapevine growth and development. Favourable conditions (solar radiation, temperature, humidity etc.) are important and have a positive effect on the growth and fruition. Critical conditions have negative influences resulting in low grape production and wine quality. The purpose of this research was to analyse the quality of wine obtained from eight grapevine varieties (four Romanian autochthonous varieties: ‘Feteasca regala’, ‘Feteasca alba’, ‘Babeasca gri’, ‘Sarba’, and four world-wide varieties: ‘Aligoté’, ‘Sauvignon Blanc’, ‘Muscat Ottonel’, and ‘Italian Riesling’). The wine samples were obtained from micro-wine production under local weather conditions of Dealu Bujoruluivineyard, Romania. The physico-chemical analysis of young wines showed that the highest alcohol content was recorded at the ‘Sauvignon blanc’ variety (14.35% vol.) followed by ‘Sarba’ (14.10% vol.). The highest level of acidity was registered to ‘Babeasca gri’ (5.90 g/L C4H6O6) and the lowest acidity in the ‘Muscat Ottonel’ wine (4.40 g/L C4H6O6). The pH values were between limits of 3.62 (‘Feteasca alba’) and 3.27 (‘Aligote’). In order to get a wider perspective about the wine quality, another 11 parameters were examined at these varieties, using spectrophotometric methods (acetic acid, potassium, calcium, free amino nitrogen, tartaric acid, copper, L-lactic acid, iron, L-malic acid, D-gluconic acid and glycerol). The results showed the suitability of ecoclimatic conditions and the proper growth and development of the tested varieties for obtaining wines withsuperiors quality.

Studying the Hydration of a Retarded Suspension of Ground Granulated Blast-Furnace Slag after Reactivation.

This article presents a combined use of a retarder (d-gluconic acid) and an alkaline activator (sodium hydroxide) in a binder system based on ground granulated blast-furnace slag. The properties of the retarder are extending the dormant hydration period and suppressing the generation of strength-giving phases. Different retarder concentrations between 0.25 and 1.00 wt.% regulate the intensity and the period of the retardation and also the characteristics of the strength development. The activator concentration of 30 and 50 wt.% regulates the overcoming of the dormant period and thereby the solution of the slag and hence the formation of the hydration products. The research objective is to produce a mineral binder system based on two separate liquid components. The highest concentration of retarder and activator generates the highest compressive strength and mass of hydration products—after 90 days of hydration a compressive strength of more than 50 N/mm2. The main phases are calcium silicate hydrate and hydrotalcite. Generally, the combination of retarder and activator shows a high potential in the performance increase of the hydration process.