In this study, the dilute maleic acid pretreatment of wheat straw is optimized, using pretreatment time, temperature and maleic acid concentration as design variables. A central composite design was ...applied to the experimental set up. The response factors used in this study are: (1) glucose benefits from improved enzymatic digestibility of wheat straw solids; (2) xylose benefits from the solubilization of xylan to the liquid phase during the pretreatment; (3) maleic acid replenishment costs; (4) neutralization costs of pretreated material; (5) costs due to furfural production; and (6) heating costs of the input materials. For each response factor, experimental data were fitted mathematically. After data translation to euro/Mg dry straw, determining the relative contribution of each response factor, an economic optimization was calculated within the limits of the design variables.
When costs are disregarded, an almost complete glucan conversion to glucose can be reached (90% from solids, 7%-10% in liquid), after enzymatic hydrolysis. During the pretreatment, up to 90% of all xylan is converted to monomeric xylose. Taking cost factors into account, the optimal process conditions are: 50 min at 170 degrees C, with 46 mM maleic acid, resulting in a yield of 65 euro/Mg (megagram = metric ton) dry straw, consisting of 68 euro/Mg glucose benefits (from solids: 85% of all glucan), 17 euro/Mg xylose benefits (from liquid: 80% of all xylan), 17 euro/Mg maleic acid costs, 2.0 euro/Mg heating costs and 0.68 euro/Mg NaOH costs. In all but the most severe of the studied conditions, furfural formation was so limited that associated costs are considered negligible.
After the dilute maleic acid pretreatment and subsequent enzymatic hydrolysis, almost complete conversion of wheat straw glucan and xylan is possible. Taking maleic acid replenishment, heating, neutralization and furfural formation into account, the optimum in the dilute maleic acid pretreatment of wheat straw in this study is 65 euro/Mg dry feedstock. This is reached when process conditions are: 50 min at 170 degrees C, with a maleic acid concentration of 46 mM. Maleic acid replenishment is the most important of the studied cost factors.
The efficiencies of fumaric, maleic, and sulfuric acid in wheat straw pretreatment were compared. As a measure for pretreatment efficiency, enzymatic digestibility of the lignocellulose was ...determined. Monomeric glucose and xylose concentrations were measured after subsequent enzymatic hydrolysis, as were levels of sugar degradation products furfural and hydroxymethylfurfural after pretreatment. The influence of pretreatment temperature and of wheat straw loading was studied. It is shown that, at 150
°C and 20–30% (w/w) dry wheat straw, the pretreatment with dilute fumaric or maleic acid can be a serious alternative to dilute sulfuric acid pretreatment.
Objectives
Relatively little is known about the incidence of long-term renal damage after renal denervation (RDN), a potential new treatment for hypertension. In this study the incidence of renal ...artery and parenchymal changes, assessed with contrast-enhanced magnetic resonance angiography (MRA) after RDN, is investigated.
Methods
This study is an initiative of ENCOReD, a collaboration of hypertension expert centres. Patients in whom an MRA was performed before and after RDN were included. Scans were evaluated by two independent, blinded radiologists. Primary outcome was the change in renal artery morphology and parenchyma.
Results
MRAs from 96 patients were analysed. Before RDN, 41 renal anomalies were observed, of which 29 mostly mild renal artery stenoses. After a median time of 366 days post RDN, MRA showed a new stenosis (25–49% lumen reduction) in two patients and progression of pre-existing lumen reduction in a single patient. No other renal changes were observed and renal function remained stable.
Conclusions
We observed new or progressed renal artery stenosis in three out of 96 patients, after a median time of 12 months post RDN (3.1%). Procedural angiographies showed that ablations were applied near the observed stenosis in only one of the three patients.
Key Points
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The incidence of vascular changes 12 months post RDN was 3.1%.
•
No renal vascular or parenchymal changes other than stenoses were observed.
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Ablations were applied near the stenosis in only one of three patients.
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► Increasing
a
w promotes dipeptide synthesis, but also – and more strongly – substrate hydrolysis. ► The pH of washing buffer has an effect on the dipeptide synthesis catalyzed by ...Alcalase CLEA-OM. ► The reaction pH neither affects dipeptide synthesis nor substrate hydrolysis. ► Optimal amounts of molecular sieves prevent substrate hydrolysis but allow enzymatic activity.
In protease-catalyzed peptide synthesis, the availability of water is essential, as a compromise must be made between on the one hand the overall enzymatic activity and, on the other hand, the rate of product synthesis. Water is essential for enzyme activity, but at the same time causes hydrolytic side reactions. We studied the coupling of the carbamoylmethyl ester of N-protected phenylalanine and phenylalanine amide in tetrahydrofuran catalyzed by Alcalase CLEA-OM at a range of water activity (
a
w) values, including the coupling in the presence of molecular sieves (
i.e. at very low
a
w values). The hydrolytic side reaction (in the present system only the hydrolysis of substrate occurs) was found to dominate above an
a
w value of about 0.2. To prevent hydrolysis, the presence of molecular sieves was found to be necessary.
Sugar degradation occurs during acid-catalyzed pretreatment of lignocellulosic biomass at elevated temperatures, resulting in degradation products that inhibit microbial fermentation in the ethanol ...production process. Arabinose, the second most abundant pentose in grasses like corn stover and wheat straw, degrades into furfural. This paper focuses on the first-order rate constants of arabinose (5
g/L) degradation to furfural at 150 and 170
°C in the presence of sulfuric, fumaric, and maleic acid and water alone. The calculated degradation rate constants (
k
d) showed a correlation with the acid dissociation constant (p
K
a), meaning that the stronger the acid, the higher the arabinose degradation rate. However, de-ionized water alone showed a catalytic power exceeding that of 50
mM fumaric acid and equaling that of 50
mM maleic acid. This cannot be explained by specific acid catalysis and the shift in p
K
w of water at elevated temperatures. These results suggest application of maleic and fumaric acid in the pretreatment of lignocellulosic plant biomass may be preferred over sulfuric acid. Lastly, the degradation rate constants found in this study suggest that arabinose is somewhat more stable than its stereoisomer xylose under the tested conditions.
The influence of end walls on segregation of bidisperse granular beds in a short rotating horizontal drum is studied by a discrete element method. Whereas non-closed periodically continued drums ...segregate radially, all simulations of drums with end walls resulted in axial segregation with two bands at low friction between the particles and the end-wall, and three bands at high friction. Various simulations show irregular transitions between two approximately equally stable states, with rapid oscillations preceding the conversions. The formation of two axial bands decreases the energy dissipation by the bed, whereas neither radial segregation nor axial segregation into three bands reduced the power absorption at constant angular velocity. Roughening up the end-walls also increased the rate of axial segregation.
Sepsis and associated organ failures confer substantial morbidity and mortality. Xanthine oxidoreductase (XOR) is implicated in the development of tissue oxidative damage in a wide variety of ...respiratory and cardiovascular disorders including sepsis and sepsis-associated acute respiratory distress syndrome (ARDS). We examined whether single nucleotide polymorphisms (SNPs) in the XDH gene (encoding XOR) might influence susceptibility to and outcome in patients with sepsis.
We genotyped 28 tag SNPs in XDH gene in the CELEG cohort, including 621 European American (EA) and 353 African American (AA) sepsis patients. Serum XOR activity was measured in a subset of CELEG subjects. Additionally, we assessed the functional effects of XDH variants utilizing empirical data from different integrated software tools and datasets.
Among AA patients, six intronic variants (rs206805, rs513311, rs185925, rs561525, rs2163059, rs13387204), in a region enriched with regulatory elements, were associated with risk of sepsis (P < 0.008-0.049). Two out of six SNPs (rs561525 and rs2163059) were associated with risk of sepsis-associated ARDS in an independent validation cohort (GEN-SEP) of 590 sepsis patients of European descent. Two common SNPs (rs1884725 and rs4952085) in tight linkage disequilibrium (LD) provided strong evidence for association with increased levels of serum creatinine (P
<0.0005 and 0.0006, respectively), suggesting a role in increased risk of renal dysfunction. In contrast, among EA ARDS patients, the missense variant rs17011368 (I703V) was associated with enhanced mortality at 60-days (P < 0.038). We found higher serum XOR activity in 143 sepsis patients (54.5 ± 57.1 mU/mL) compared to 31 controls (20.9 ± 12.4 mU/mL, P = 1.96 × 10
). XOR activity was associated with the lead variant rs185925 among AA sepsis patients with ARDS (P < 0.005 and P
<0.01). Multifaceted functions of prioritized XDH variants, as suggested by various functional annotation tools, support their potential causality in sepsis.
Our findings suggest that XOR is a novel combined genetic and biochemical marker for risk and outcome in patients with sepsis and ARDS.
•Alcalase covalently immobilized onto acrylic beads (Cov), itself, hardly inactivates in THF.•With molecular sieve beads, Cov loses activity over time in THF.•The instability of Cov is mainly caused ...by the mechanical damage of Cov by the molecular sieve beads.•Intermediate rehydration of Cov, required for its reuse, leads to some activity loss.
The long-term stability and re-use of Alcalase covalently immobilized onto macroporous acrylic beads (Cov) in tetrahydrofuran (THF) were investigated. Cov can be used to synthesize dipeptides under near-anhydrous conditions in THF. Cov was incubated with and without molecular sieves (beads or powder) in THF, in order to investigate whether its stability is affected by the presence of molecular sieves. After different incubation periods, the enzyme activity was determined in an aqueous environment. In addition, Cov was repeatedly recycled to examine its reusability. Without molecular sieve beads, Cov hardly inactivated in THF. With molecular sieve beads, Cov lost activity over time. Incubated Cov samples were rotated on a blood rotator, entailing mechanical forces between Cov and the molecular sieve beads. Mechanical damage of Cov by the molecular sieve beads was found to be the main reason for the instability of Cov. During reuse, intermediate rehydration of Cov also caused a small but significant activity loss.
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