This work aimed at the production of stabilized derivatives of Thermomyces lanuginosus lipase (TLL) by multipoint covalent immobilization of the enzyme on chitosan-based matrices. The resulting ...biocatalysts were tested for synthesis of biodiesel by ethanolysis of palm oil. Different hydrogels were prepared: chitosan alone and in polyelectrolyte complexes (PEC) with κ-carrageenan, gelatin, alginate, and polyvinyl alcohol (PVA). The obtained supports were chemically modified with 2,4,6-trinitrobenzene sulfonic acid (TNBS) to increase support hydrophobicity, followed by activation with different agents such as glycidol (GLY), epichlorohydrin (EPI), and glutaraldehyde (GLU). The chitosan-alginate hydrogel, chemically modified with TNBS, provided derivatives with higher apparent hydrolytic activity (HAapp) and thermal stability, being up to 45-fold more stable than soluble lipase. The maximum load of immobilized enzyme was 17.5 mg g−1 of gel for GLU, 7.76 mg g−1 of gel for GLY, and 7.65 mg g−1 of gel for EPI derivatives, the latter presenting the maximum apparent hydrolytic activity (364.8 IU g−1 of gel). The three derivatives catalyzed conversion of palm oil to biodiesel, but chitosan-alginate-TNBS activated via GLY and EPI led to higher recovered activities of the enzyme. Thus, this is a more attractive option for both hydrolysis and transesterification of vegetable oils using immobilized TLL, although industrial application of this biocatalyst still demands further improvements in its half-life to make the enzymatic process economically attractive.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Legacies of Crime explores the lives of seriously delinquent girls and boys in the United States who were followed over a twenty-year period as they grew to adulthood. In-depth interviews with these ...women and men and their children - a majority now adolescents themselves - depict the adults' economic and social disadvantages and continued criminal involvement, and in turn the unique vulnerabilities of their children. Giordano identifies family dynamics that foster the intergenerational transmission of crime, violence, and drug abuse, rejecting the notion that such continuities are based solely on genetic similarities or even lax, inconsistent parenting. The author breaks new ground in directly exploring - and in the process revising - the basic tenets of classic social learning theories, and confronting the complications associated with the parent's gender. Legacies of Crime also identifies factors associated with resilience in the face of what is often a formidable package of risks favoring intergenerational continuity.
•Immobilization of Bacillus subtillis recombinant endoxylanase with remarkable stabilization.•Enzyme supported in agarose-glyoxal was 8600-fold more stable than in soluble form.•Enzyme structure ...showing the location of its five Lys may explain this behavior.•Hydrolysis of xylan (soluble and insoluble fractions) with 23% max xylan conversion.•X2, X3 and X4 produced without xylose. Catalyst yield invariant after 10 cycles.
Xylooligosaccharides (XOs) are small oligomers constituted by 2−10 units of xylan monomers, with important nutraceutical properties. They can be produced through hydrolysis of xylan catalyzed by an endoxylanase. The use of immobilized and stabilized enzymes may decrease the industrial process costs. In this study, XynA, a recombinant enzyme from B. subtilis, was immobilized in three different supports: agarose and chitosan activated with glyoxal groups and chitosan activated with glutaraldehyde. High immobilization yields were obtained, 100% for agarose-glyoxal and chitosan-glutaraldehyde, 82% for chitosan-glyoxal, with recovered activities of 42.7 (±1.3), 10.7±0.8 and 53.6% (± 1.7), respectively. A great increase in the thermal stability of the enzyme (at 56°C, pH 5.5) was achieved for the glyoxal derivatives: 75-fold for chitosan and 8600-fold for agarose. The great thermal stability obtained to the derivative agarose-glyoxal can be explained by the enzyme immobilization through lysine residues located in unstable sites of the protein structure. The agarose-glyoxal derivative was tested in the production of XOs (X2, X3 and X4) from soluble and conventional birchwood xylan, reaching approximately 20% of conversion in 3h and 23% in 24h, without the undesirable xylose production. After 10 cycles of hydrolysis, the conversion remained almost unchanged.
ABSTRACT
In this work we apply the Shannon entropy based method to derive a diffusion or instability time in a triaxial model resembling an elliptical galaxy. We succeed in getting an accurate ...time-scale for diffusion using this novel technique after adopting a particular initial starting space, the one defined by the unperturbed integrals of the system. Comparisons with other standard techniques, such as a least-squares fit on the variance evolution of the integrals and the straight numerical integrations of the equations of motion, are included. The physical results provided in this effort reveal that the role of chaotic motion in triaxial galactic models is almost irrelevant in galactic time-scales, in agreement with previous qualitative approaches to this issue.
Xylooligosaccharides (XOS) are nondigestible compounds of great interest for food and pharmaceutical industries due to their beneficial prebiotic, antibacterial, antioxidant, and antitumor ...properties. The market size of XOS is increasing significantly, which makes its production from lignocellulosic biomass an interesting approach to the valorization of the hemicellulose fraction of biomass, which is currently underused. This review comprehensively discusses XOS production from lignocellulosic biomass, aiming at its application in integrated biorefineries. A bibliometric analysis is carried out highlighting the main players in the field. XOS production yields after different biomass pretreatment methods are critically discussed using Microsoft PowerBI® (2.92.706.0) software, which involves screening important trends for decision-making. Enzymatic hydrolysis and the major XOS purification strategies are also explored. Finally, the integration of XOS production into biorefineries, with special attention to economic and environmental aspects, is assessed, providing important information for the implementation of biorefineries containing XOS in their portfolio.
► Lipases were immobilized by physical adsorption on poly-hydroxybutyrate (PHB) beads. ► Large beads PHB derivatives (LPHB) presented strong diffusional limitations on the olive oil hydrolysis. ► ...Particle size of the support did not have influence on the butyl butyrate synthesis. ► PFL immobilized on LPHB gave the highest productivity in ethyl esters synthesis. ► BTL2 was found to be highly active in the ester synthesis reactions.
Five microbial lipase preparations from several sources were immobilized by hydrophobic adsorption on small or large poly-hydroxybutyrate (PHB) beads and the effect of the support particle size on the biocatalyst activity was assessed in the hydrolysis of olive oil, esterification of butyric acid with butanol and transesterification of babassu oil (Orbignya sp.) with ethanol. The catalytic activity of the immobilized lipases in both olive oil hydrolysis and biodiesel synthesis was influenced by the particle size of PHB and lipase source. In the esterification reaction such influence was not observed. Geobacillus thermocatenulatus lipase (BTL2) was considered to be inadequate to catalyze biodiesel synthesis, but displayed high esterification activity. Butyl butyrate synthesis catalyzed by BTL2 immobilized on small PHB beads gave the highest yield (≈90mmolL−1). In biodiesel synthesis, the catalytic activity of the immobilized lipases was significantly increased in comparison to the free lipases. Full conversion of babassu oil into ethyl esters was achieved at 72h in the presence of Pseudozyma antarctica type B (CALB), Thermomyces lanuginosus lipase (Lipex® 100L) immobilized on either small or large PHB beads and Pseudomonas fluorescens (PFL) immobilized on large PHB beads. The latter preparation presented the highest productivity (40.9mg of ethyl estersmg−1 immobilized proteinh−1).
The detection of recurrent mutations affecting the hormone binding domain (HBD) of estrogen receptor alpha (ERα/ESR1) in endocrine therapy-resistant and metastatic breast cancers has prompted ...interest in functional characterization of these genetic alterations. Here, we explored the role of HBD-ESR1 mutations in influencing the behavior of breast cancer stem cells (BCSCs), using various BC cell lines stably expressing wild-type or mutant (Y537 N, Y537S, D538G) ERα. Compared to WT-ERα clones, mutant cells showed increased CD44+/CD24- ratio, mRNA levels of stemness genes, Mammosphere Forming Efficiency (MFE), Self-Renewal and migratory capabilities. Mutant clones exhibited high expression of NOTCH receptors/ligands/target genes and blockade of NOTCH signaling reduced MFE and migratory potential. Mutant BCSC activity was dependent on ERα phosphorylation at serine 118, since its inhibition decreased MFE and NOTCH4 activation only in mutant cells. Collectively, we demonstrate that the expression of HBD-ESR1 mutations may drive BC cells to acquire stem cell traits through ER/NOTCH4 interplay. We propose the early detection of HBD-ESR1 mutations as a challenge in precision medicine strategy, suggesting the development of tailored-approaches (i.e. NOTCH inhibitors) to prevent disease development and metastatic spread in BC mutant-positive patients.
•ESR1 hormone binding domain mutations increase breast cancer stem cell activity.•NOTCH activation promotes stemness phenotype in mutant-positive breast cancer cells.•ERα S118 phosphorylation sustains NOTCH activation and stemness in mutant clones.•NOTCH-tailored therapy may be suitable in breast cancer mutant-positive patients.
Abstract The interplay between vitamin D and the growth hormone (GH)/insulin-like growth factor (IGF)-I system is very complex and to date it is not fully understood. GH directly regulates renal 1 ...alpha-hydroxylase activity, although the action of GH in modulating vitamin D metabolism may also be IGF-I mediated. On the other hand, vitamin D increases circulating IGF-I and the vitamin D deficiency should be normalized before measurement of IGF-I concentrations to obtain reliable and unbiased IGF-I values. Indeed, linear growth after treatment of nutritional vitamin D deficiency seems to be mediated through activation of the GH/IGF-I axis and it suggests an important role of vitamin D as a link between the proliferating cartilage cells of the growth plate and GH/IGF-I secretion. Vitamin D levels are commonly lower in patients with GH deficiency (GHD) than in controls, with a variable prevalence of insufficiency or deficiency, and this condition may worsen the already known cardiovascular and metabolic risk of GHD, although this finding is not common to all studies. In addition, data on the impact of GH treatment on vitamin D levels in GHD patients are quite conflicting. Conversely, in active acromegaly, a condition characterized by a chronic GH excess, both increased and decreased vitamin D levels have been highlighted, and the interplay between vitamin D and the GH/IGF-I axis becomes even more complicated when we consider the acromegaly treatment, both medical and surgical. The current review summarizes the available data on vitamin D in the main disorders of the GH/IGF-I axis, providing an overview of the current state of the art.
A major environmental pollution problem is the release into the atmosphere of particulate matter, including nanoparticles (NPs), which causes serious hazards to human and ecosystem health, ...particularly in urban areas. However, knowledge about the uptake, translocation and accumulation of NPs in plant tissues is almost completely lacking. The uptake of silver nanoparticles (Ag-NPs) and their transport and accumulation in the leaves, stems and roots of three different tree species, downy oak (Quercus pubescens Willd.), Scots pine (Pinus sylvestris L.) and black poplar (Populus nigra L.), were assessed. In the experiment, Ag-NPs were supplied separately to the leaves (via spraying, the foliar treatment) and roots (via watering, the root treatment) of the three species. Uptake, transport and accumulation of Ag were investigated through spectroscopy. The concentration of Ag in the stem was higher in the foliar than in the root treatment, and in poplar more than in oak and pine. Foliar treatment with Ag-NPs reduced aboveground biomass and stem length in poplars, but not in oaks or pines. Species-specific signals of oxidative stress were observed; foliar treatment of oak caused the accumulation of H2O2 in leaves, and both foliar and root treatments of poplar led to increased O2- in leaves. Ag-NPs affected leaf and root bacteria and fungi; in the case of leaves, foliar treatment reduced bacterial populations in oak and poplar and fungi populations in pine, and in the case of roots, root treatment reduced bacteria and increased fungi in poplar. Species-specific mechanisms of interaction, transport, allocation and storage of NPs in trees were found. We demonstrated definitively that NPs enter into the tree stem through leaves faster than through roots in all of the investigated tree species.
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