Benefits of β-xylanase for wheat biomass conversion to bioethanol

BACKGROUND: The efficiency of bioethanol production from wheat biomass is related to the quality of end products as well as to safety criteria of co‐products such as distiller's dried grains with solubles (DDGS). The inclusion of a new biocatalyst for non‐starch polysaccharide degradation in fermentation processes could be one of the solutions. The objective of this study was to evaluate the influence of β‐xylanases in combination with traditional amylolytic enzymes on the efficiency of bioethanol production and DON detoxification during fermentation of Fusarium‐contaminated wheat biomass with high concentration of deoxynivalenol (DON; 3.95 mg kg^?1). RESULTS: The results showed that the negative effect of Fusarium spp. on yield and quality of bioethanol could be eliminated by the application of Trichoderma reesei xylanase in combination with amylolytic enzymes. This technological solution allowed to increase the concentration of ethanol in the fermented wort by 35.3% and to improve the quality of bioethanol by decreasing the concentrations of methanol, methyl acetate, isoamyl and isobutyl alcohols. Mass balance calculations showed that DDGS was the main source of DON contamination, comprising 74% of toxin found in wheat biomass. By using new enzyme combination for wheat biomass saccharification, a higher level of detoxification (41%) of DON was achieved during the fermentation process. CONCLUSION: The addition of Trichoderma reesei xylanase played a positive role in bioethanol production from Fusarium‐contaminated wheat biomass, indicating that the yeast‐growing medium was enriched during the enzymatic treatment. Copyright © 2011 Society of Chemical Industry     

Contribution of biomass burning to atmospheric polycyclic aromatic hydrocarbons at three European background sites

Radiocarbon analysis of atmospheric polycyclic aromatic hydrocarbons (PAHs) from three background areas in Sweden, Croatia, and Greece was performed to apportion their origin between fossil and biomass combustion. Diagnostic ratios of PAHs implied that wood and coal combustion was relatively more important in the northern European site, while combustion of fossil fuels was the dominant source of PAHs to the two central-southern European background sites. The radiocarbon content (delta14C) of atmospheric PAHs in Sweden ranged between -388 per thousand and -381 per thousand, while more depleted values were observed for Greece (-914 per thousand) and Croatia (-888 per thousand). Using a 14C isotopic mass balance model it was calculated that biomass burning contributes nearly 10% of the total PAH burden in the studied southern European atmosphere with fossil fuel combustion making up the 90% balance. In contrast, biomass burning contributes about 50% of total PAHs in the atmosphere at the Swedish site. Our results suggest that the relative contributions of biomass burning and fossil fuels to atmospheric PAHs may differ considerably between countries, and therefore, different national control strategies might be needed if a further reduction of these pollutants is to be achieved on a continental-global scale.     

Developing strategies for robust energy systems. II: Application to CO2 risk management

One of the most important determinants for the design of the future energy system is whether or not constraints on CO₂ emissions will be imposed. Here, this issue is treated as a decision under uncertainty. Three strategies have been considered: immediate action to adapt to a future emission constraint (Commitment), business as usual (No Hedging), and hedging (Hedging). In the case of hedging, preparations are made outside the energy system, but the energy system itself is allowed to develop according to baseline assumptions until the uncertainty has been resolved. The IEA-MARKAL model has been used to show how efficient and robust the three strategies are under different developments. The development of the Swedish energy system has been studied for two rates of economic growth in combination with three nuclear policies and two CO₂ policies. The value of preparations for meeting a possible restriction on CO₂ emissions, i.e., following either the Commitment or the Hedging strategy, is considerably higher when the energy demand increases rapidly. In the low growth case, the choice of strategy is largely dependent upon the decision maker's estimate of the likelihood of an emission cap. In the high growth case, this likelihood must be considered to be very small in order to choose the No Hedging strategy, even with reinvestments in nuclear capacity beyond 2010.     

A synthetic IgG-binding domain based on staphylococcal protein A

A synthetic IgG-binding domain based on staphylococcal proteinA was designed with the aid of sequence comparisons and computergraphic analysis. A strategy, utilizing non-palindromic restrictionsites, was used to overcome the difficulties of introducingshe-specific changes into the repetitive gene. A single mutagenizedgene fragment was polymerized to different multiplicities, andthe different gene products were expressed in Escherichia coli.Using this scheme, protein A-like proteins composed of differentnumbers of IgG-binding domains were produced. These domainswere changed to lack asparagine-glycine dipeptide sequencesas well as methionine residues and are thus, in contrast tonative protein A, resistant to treatment with hydroxylamineand cyanogen bromide.     

NMDA receptor complex blockade by oral administration of magnesium: comparison with MK-801

The ion channel of the N-methyl-D-aspartate (NMDA) receptor complex is subject to a voltage-dependent regulation by Mg2+ cations. Under physiological conditions, this channel is supposed to be blocked by a high concentration of magnesium in extracellular fluids. A single dose of magnesium organic salts (i.e., aspartate, pyroglutamate, and lactate) given orally to normal mice rapidly increases the plasma Mg2+ level and reveals a significant dose-dependent antagonist effect of magnesium on the latency of NMDA-induced convulsions; this effect is similar to that seen after administration of the dizocilpine (MK-801) channel blocker. An anticonvulsant effect of Mg2+ treatment is also observed with strychnine-induced convulsions but not with bicuculline-, picrotoxin-, or pentylenetetrazol-induced convulsions. In the forced swimming test, Mg2+ salts reduce the immobility time in a way similar to imipramine and thus resemble the antidepressant-like activity of MK-801. This activity is masked at high doses of magnesium by a myorelaxant effect that is comparable to MK-801-induced ataxia. Potentiation of yohimbine fatal toxicity is another test commonly used to evaluate putative antidepressant drugs. Administration of Mg2+ salts, like administration of imipramine strongly potentiates yohimbine lethality in contrast to MK-801, which is only poorly active in this test. Neither Mg2+ nor MK-801 treatment can prevent reserpine-induced hypothermia. These data demonstrate that oral administration of magnesium to normal animals can antagonize NMDA-mediated responses and lead to antidepressant-like effects that are comparable to those of MK-801. This important regulatory role of Mg2+ in the central nervous system needs further investigation to evaluate the potential therapeutic advantages of magnesium supplementation in psychiatric disorders.     

Linear pseudosystolic array for partitioned matrix algorithms

We describe a class-specific linear pseudosystolic array, withK processing elements, suitable for partitioned execution of matrix algorithms. This array achieves high efficiency, exploits pipelining within cells in a simple manner, has off-cells communication rate lower than computation rate, a small storage inside each cell (whose size is independent of the size of problems), and external storage. This array has been derived from the application of the multimesh graph (MMG) method to a large class of matrix algorithms.Processing elements (cells) use the decoupled access/execute model of computation, which requires two programs in each cell: one controlling the execution of operations and the other the data transfers. All storage modules in the array are accessed as FIFO queues, without the need for addressing mechanisms. We describe the proposed instruction set, which includes single-instruction loops with no overhead, and block-loops with just one extra instruction. Moreover, cells can nest up to three loops with no added overhead. These features are needed for mapping algorithms with the MMG method.Mapping onto this array is illustrated using the LU-decomposition algorithm, and results obtained with other algorithms are also given. Estimates of performance indicate that it is possible to achieve over 85% efficiency, with low requirements in communication bandwidth and storage.This research has been supported in part by Universidad de Concepción (Grant DI-20.92.21, Linear array for matrix algorithms) and by NSF (Grant MIP-8813340, Composite operations using on-line arithmetic in application-specific parallel architectures).     

Shrinkage reduction and morphological characterization of PP reinforced with glass fiber and nanoclay using functionalized PP as compatibilizer

This work presents results of shrinkage and structure characteristics of reinforced PP using combinations of glass fiber and nanoclay with functionalized PP as compatibilizer during injection molding. Shrinkage, warpage and structure characteristics of clay-fiber reinforced nanocomposites using PP grafted with 2-[2- (Dimethylamino) ethoxy] ethanol (DMAE) to obtain PPgDMAE as compatibilizer, were analyzed. The glass fiber-nanoclay combinations decrease the PP shrinkage as well as the warpage tendency. Functionalized PP facilitates glass fiber and clay dispersion and intercalation. The crystallization temperature, Tc, increases slightly with respect to pure PP and the degree of crystallinity, Xc, was reduced with the clay content.     

On the syntheses of branched saturated fatty acids

In order to investigate the relation between the structure of mono-branched saturated fatty acids and their physical properties, a three-factor central composite design was constructed. For this purpose sixteen different fatty acids were prepared. The synthetic strategy was to use if possible, a few common starting materials for the preparation of most of the acids. Thus alkylation and hydrolysis of oxazolines were used for the preparation of 2-butylhexanoic acid, 2-methyloctadecanoic acid, 2-hexadecyloctadecanoic acid and 2-pentyloctadecanoic acid. A number of acids were prepared from thiophene derivatives followed by desulfurization with Raney-Nickel alloy under alkaline conditions. Thus, starting from 3-ethylthiophene, 4-ethyl-2-thiophenecarboxylic acid and 4-ethyl-2-methyl-5-thiophenecarboxylic acid were prepared, which upon desulfurization gave the desired 4-methylhexanoic acid. From 3-bromo-2-methylthiophene, 3-ethyl-2-methyl-5-thiophenecarboxylic acid was preparedvia 3-acetyl-2-methylthiophene and 3-ethyl-2-methylthiophene. Desulfurization gave 4-ethylhexanoic acid. Another approach started with 2-acylthiophenes, which were reacted with Grignard reagent to yield the appropriate olefins. By metalation and reaction with carbon dioxide, these were transformed to the corresponding 2-thiophenecarboxylic acids. Upon desulfurization, the desired fatty acids were obtained. In this way 6-propyldecanoic acid, 6-hexyldodecanoic acid, 6-methyldodecanoic acid and 6-pentylpentadecanoic acid were prepared. The remaining four acids were prepared from some of the branched acids described above through Kolbe reactions of dioic acids. Thus 16-methyloctadecanoic acid and 10-methyl-dodecanoic acid were obtained from 4-methylhexanoic acid, 16-ethyloctadecanoic acid from 4-ethylhexanoic acid and 9-pentyloctadecanoic acid from 6-pentylpentadecanoic acid.     

Equilibrium approaches to natural water systems—6. Acid-base properties of a concentrated bog-water and its complexation reactions with aluminium(III)

A filtered bog-water, concentrated by means of a freezing technique, has been studied with respect to acid-base properties and aluminium(III) complexation reactions. Sampling was performed during autumn and winter periods with a resulting acidity or alkalinity due to oxic (autumn) or anoxic (winter) conditions. The measurements were performed as potentiometric titrations in constant ionic media (0.02, 0.1 and 0.6 M NaCl) with the use of a glass electrode. The samples show buffer ranges at 3 pH 5 and pH 7.5. The first is ascribed to the presence of carboxylate groups and is characterized by fast equilibria. The second is due to phenolic OH⁻ groups and precipitation reactions with resulting sluggish equilibria. For one sampling period comprehensive measurements were undertaken to study the possible polyelectrolytic character of the organic acids. Due to the small increase in apparent carboxylate pKa-values with the degree of dissociation at low (0.02 M) as well as at high (0.6 M) ionic strength, the possible polyelectrolytic feature of the acids was neglected. Instead, a good fit to data was obtained by introducing a di-protic acid (H₂L) as a model compound. Furthermore the medium dependence of the two acidity constants could satisfactorily be fitted to the expression:

Full-size image (1K)

, where K is the constant at infinite dilution, a and b parameters of which b has been adjusted to present data. The following K values were obtained: pK₁ = 3.65 and pK₂ = 4.30. The complexation with Al(III) could be described by the formation of AlL⁺, AlL₂⁻ and the ternary species AlLH₋₁. The stability constants (log k₁ = 4.4 (winter), 4.2 (autumn); log k₂ = 4.2, 4.7; pKa (AlL⁺) = 4.2, 4.2) show no significant trend with sampling period but indicate a stability of the complexes greater than for phtalic acid but lower than for oxalic acid. Finally, the theoretical solubility of the clay mineral kaolinite in the presence of bog-water was computer modelled. The calculations show up on a 10-fold increase with respect to soluble aluminium at pH = 5.