Search Results (39)

Four new minor monosulfated triterpene penta- and hexaosides, cladolosides S (1), S₁ (2), T (3), and T₁ (4), were isolated from the Vietnamese sea cucumber Cladolabes schmeltzii (Sclerodactylidae, Dendrochirotida). The structures of the compounds were established based on extensive analysis of 1D and 2D NMR spectra as well as HR-ESI-MS data. Cladodosides S (1), S₁ (2) and T (3), T₁ (4) are two pairs of dehydrogenated/hydrogenated compounds that share identical carbohydrate chains. The oligosaccharide chain of cladolosides of the group S is new for the sea cucumber glycosides due to the presence of xylose residue attached to C-4 Xyl1 in combination with a sulfate group at C-6 MeGlc4. The oligosaccharide moiety of cladolosides of the group T is unique because of the position of the sulfate group at C-3 of the terminal sugar residue instead of the 3-O-Me group. This suggests that the enzymatic processes of sulfation and O-methylation that occur during the biosynthesis of glycosides can compete with each other. This can presumably occur due to the high level of expression or activity of the enzymes that biosynthesize glycosides. The mosaicism of glycoside biosynthesis (time shifting or dropping out of some biosynthetic stages) may indicate a lack of compartmentalization inside the cells of organism producers, leading to a certain degree of randomness in enzymatic reactions; however, this also offers the advantage of providing chemical diversity of the glycosides. Analysis of the hemolytic activity of a series of 26 glycosides from C. schmeltzii revealed some patterns of structure–activity relationships: the presence or absence of 3-O-methyl groups has no significant impact, hexaosides, which are the final products of biosynthesis and predominant compounds of the glycosidic fraction of C. schmeltzii, are more active than their precursors, pentaosides, and the minor tetraosides, cladolosides of the group A, are weak membranolytics and therefore are not synthesized in large quantities. Two glycosides from C. schmeltzii, cladolosides D (18) and H₁ (26), display selectivity of cytotoxic action toward triple-negative breast cancer cells MDA-MB-231, while remaining non-toxic in relation to normal mammary cells MCF-10A. Quantitative structure–activity relationships (QSAR) were calculated based on the correlational analysis of the physicochemical properties and structural features of the glycosides and their hemolytic and cytotoxic activities against healthy MCF-10A cells and cancer MCF-7 and MDA-MB-231 cell lines. QSAR highlighted the complexity of the relationships as the cumulative effect of many minor contributions from individual descriptors can have a significant impact. Furthermore, many structural elements were found to have different effects on the activity of the glycosides against different cell lines. The opposing effects were especially pronounced in relation to hormone-dependent breast cancer cells MCF-7 and triple-negative MDA-MB-231 cells. Full article

Xylitol is a sugar–alcohol compound with broad applications in fields such as the food, dental, and pharmaceutical sectors. Although xylitol biosynthesis has gained attention, the current strategy for industrial xylitol production majorly relies on the chemical hydrogenation of xylose, which is energy-intensive and environmentally harmful. In this study, the toxicity of xylitol toward Escherichia coli was first examined, and the result demonstrated that Escherichia coli is robust against xylitol at 150 g/L. Genes encoding xylose reductases from different microorganisms were then selected and compared for xylitol production in different E. coli strains. The introduction of xylose reductase of Zymomonas mobilis, driven by the constitutive strong promoter Pgap or Pgap-6M into E. coli, resulted in the accumulation of xylitol at a titer of 64.1 g/L. The increase in NADPH by overexpressing the soluble pyridine nucleotide transhydrogenase encoded by sthA improved the xylitol titer to 83.5 g/L. Seven genes encoding xylose transporters, such as XylE and XylFGH, as well as five mutants of the xylose symporter Glf were then overexpressed and compared for xylitol production. Mutant glf^L445I exhibited the highest improvement in xylitol production at a titer of 88.4 ± 0.7 g/L and a yield of 0.95 g/g. Our study thus demonstrated that xylose reductase derived from Z. mobilis is the best one for xylitol production in E. coli, and xylitol production can be further improved by combining diverse metabolic engineering strategies. Our study, thus, provides efficient xylose reductase and a recombinant strain for future industrial xylitol production. Full article

This study explores the oxidation and racemization of selected C5 and C6 sugars using hydrogen peroxide (H₂O₂) in alkaline and Fenton reaction conditions. The sugars studied include D-Glucose, D-Fructose, D-Mannose, D-Xylose, D-Lactose, D-Arabinose, D-Cellobiose, Sucrose, and D-Galactose. Oxidation reactions were conducted using both Fenton’s reagent and NaOH/H₂O₂ to examine product formation, yield distribution, and stereochemical transformations. Under alkaline conditions, sugars primarily oxidized to yield sodium formate and hydrogen, with the minimal formation of intermediate sugar acids. Excess alkaline conditions further promoted the rapid degradation of sugars to sodium formate and hydrogen as primary products, indicating the strong influence of reaction conditions on oxidation pathways. A significant observation was that both alkaline and Fenton oxidation led to racemization, converting optically pure sugars into a racemic mixture of D- and L-enantiomers, thus producing products with zero optical rotation. The generation of L-enantiomers, metabolically inactive in biological systems, has implications for energy yield and biochemical efficiency. Full article

This article presents the conditions for the transformation of pulp containing mixtures that occur in the hemicellulose fraction derived from lignocellulosic biomass. Selected materials with strong acid centers were used as catalytic materials: ion exchange resins, including AMBERLYST 15(H) and DOWEX DR-G8(H), and selected zeolite in the hydrogen form of the Beta type (H-BEA). The group was marked with the abbreviations M1, M2 and M3, where it differs in the content of xylose, mannose, galactose, glucose, rhamnose and uronic acids. The catalytic process was carried out in the reactor as a one-pot technique at temperatures of 180–250 °C for 1–5 h. Based on the collected results, the transformation products of hemicellulose pulp were determined and the catalytic abilities of selected materials were determined. The proposed conditions led to the production of organic acids. Levulinic acid was obtained with a selectivity of 25.95% after 1 h of the process at a temperature of 250 °C with the participation of H-BEA, and lactic acid was obtained with a selectivity of 73.28% after 5 h of the process at a temperature of 250 °C using DOWEX DRG8(H). The presence of oxalic, propionic and acetic acids was also observed. Full article

This work studies the partition of phenolic compounds, namely caffeic acid, syringic acid, vanillic acid, ferulic acid, and vanillin, in aqueous two-phase systems (ATPSs) formed by acetonitrile and deep eutectic solvents (DESs) based on choline chloride ([Ch]Cl) and carbohydrates (sucrose, d-glucose, d-mannose, arabinose, and d-xylose). The binodal curves built at 25 °C and 0.1 MPa using DES were compared with ATPS composed of [Ch]Cl and the same carbohydrates. The ability to form ATPS depends on the number and kind of hydroxyl groups in DES’s hydrogen-bond donor compound (carbohydrates). ATPS based on DES showed biphasic regions larger than the systems based on [Ch]Cl and carbohydrates alone due to the larger hydrophilicity of DES. The ATPS were used to study the partition of the phenolic compounds. For all the systems, the biomolecules preferentially partitioned to the acetonitrile-rich phase (K > 1), and the best recovery in the top phase ranged between 53.36% (caffeic acid) and 90.09% (vanillin). According to the remarkable results, DES-based ATPS can selectively separate ferulic acid and vanillin for the top phase and syringic, caffeic, and vanillic acids for the bottom phase, achieving a selectivity higher than two. Full article

This study attempts to overcome the challenges associated with the degradation of complex organic substances like corn straw hydrolysate in hydrogen recovery by strategically enriching functional microbial communities in single-chamber cubic microbial electrolysis cells (MECs). We applied negative pressure, using acetate or xylose as electron donors, to mitigate the hydrogen sink issues caused by methanogens. This innovative method significantly enhanced MEC performance. MECs enriched with xylose demonstrated superior performance, achieving a hydrogen production rate 3.5 times higher than that achieved by those enriched with acetate. Under negative pressure, hydrogen production in N-XyHy10 reached 0.912 ± 0.08 LH₂/L MEC/D, which was 6.7 times higher than in the passive-pressure MECs (XyHy10). This advancement also resulted in substantial increases in current density (73%), energy efficiency (800%), and overall energy efficiency (540%) compared with MECs operated under passive pressure with 10% hydrolysate feed. The enrichment of polysaccharide-degrading bacteria such as Citrobacter and Pseudomonas under negative pressure underscores the potential for their industrial application in harnessing complex organic substrates for bioenergy production in single-chamber MECs. This is a promising approach to scaling up bioenergy recovery processes. The findings of this research study contribute significantly to the field by demonstrating the efficacy of negative pressure in enhancing microbial activity and energy recovery, thereby offering a promising strategy for improving bioenergy production efficiency in industries. Full article

Hydrogen is a well-known clean energy carrier with a high energetic yield. Its versatility allows it to be produced in diverse ways, including biologically. Specifically, dark fermentation takes advantage of organic wastes, such as agro-industrial residues, to obtain hydrogen. One of these harmful wastes that is poorly discharged into streams is sugarcane bagasse pentose liquor (SBPL). The present study aimed to investigate hydrogen generation from SBPL fermentation in batch reactors by applying different food/microorganism (2–10 F/M) and carbon/nitrogen (10–200 C/N) ratios under mesophilic and thermophilic conditions. Biohydrogen was produced in all pentose liquor experiments along with other soluble microbial products (SMPs): volatile fatty acids (VFAs) (at least 1.38 g L⁻¹ and 1.84 g L⁻¹ by the average of C/N and F/M conditions, respectively) and alcohols (at least 0.67 g L⁻¹ and 0.325 g L⁻¹ by the average of C/N and F/M conditions, respectively). Thermophilic pentose liquor reactors (t-PLRs) showed the highest H₂ production (H₂ maximum: 1.9 ± 0.06 L in 100 C/N) and hydrogen yield (HY) (1.9 ± 0.54 moles of H₂ moles of substrate⁻¹ in 2 F/M) when compared to mesophilic ones (m-PLRs). The main VFA produced was acetate (>0.85 g L⁻¹, considering the average of both nutritional conditions), especially through the butyrate pathway, which was the most common metabolic route of experimental essays. Considering the level of acid dilution used in the pretreatment of bagasse (H₂SO₄ (1%), 1.1 atm, 120 °C, 60 min), it is unlikely that toxic compounds such as furan derivatives, phenol-like substances (neither was measured), and acetate (<1.0 g L⁻¹) hinder the H₂ production in the pentose liquor reactors (PLRs). Sugarcane bagasse pentose liquor fermentation may become a suitable gateway to convert a highly polluting waste into a renewable feedstock through valuable hydrogen production. Full article

Methane, a potent greenhouse gas, represents both a challenge and an opportunity in the quest for sustainable energy. This work investigates the biotechnology for converting methane into clean, renewable hydrogen. The co-culture of Chlorella sacchrarophila FACHB 4 and Methylomonas sp. HYX-M1 was demonstrated to completely convert 1 mmol of methane to biomass within 96 h. After acid digestion of such biomass, up to 45.05 μmol of glucose, 4.07 μmol of xylose, and 26.5 μmol of lactic acid were obtained. Both Clostridium pasteurianum DSM525 and Clostridium sp. BZ-1 can utilize those sugars to produce hydrogen without any additional organic carbon sources. The higher light intensity in methane oxidation co-culture systems resulted in higher hydrogen production, with the BZ-1 strain producing up to 14.00 μmol of hydrogen, 8.19 μmol of lactate, and 6.09 μmol of butyrate from the co-culture biomass obtained at 12,000 lux. The results demonstrate that the co-culture biomass of microalgae and methanotroph has the potential to serve as a feedstock for dark fermentative hydrogen production. Our study highlights the complexities inherent in achieving efficient and complete methane-to-hydrogen conversion, positioning this biological approach as a pivotal yet demanding area of research for combating climate change and propelling the global energy transition. Full article

Dihydromyricetin (DMY) has been encapsulated in delivery systems to address the solubility limitations of DMY in water and improve its bioavailability. Air-assisted electrospinning has been used as a novel technology to load DMY. To evaluate the impact of adding DMY to dextran/zein nanofibers and understand the effects of the Maillard reaction (MR) on the physical and functional properties of DMY-loaded nanofibers, dextran/zein/xylose nanofibers with 0%, 1%, 2%, 3%, and 4% DMY were fabricated, followed by MR crosslinking. Scanning electron microscopy (SEM) observations indicated that the addition of DMY and the MR did not affect the morphology of the nanofibers. X-ray diffraction (XRD) results indicated amorphous dispersion of DMY within the nanofibers and a decreased crystalline structure within the nanofibers following the MR, which might improve their molecular flexibility. The nanofibrous film formed after the MR exhibited both increased tensile strength and elastic modulus due to hydrogen bonding within the nanofibers and increased elongation at break attributed to the increased amorphization of the structure after crosslinking. The nanofibers were also found to exhibit improved heat stability after the MR. The antioxidant activity of the nanofibers indicated a dose-dependent effect of DMY on radical scavenging activity and reducing power. The maintenance of antioxidant activity of the nanofibers after the MR suggested heat stability of DMY during heat treatment. Overall, dextran/zein nanofibers with various DMY contents exhibited tunable physical properties and effective antioxidant activities, indicating that dextran/zein nanofibers offer a successful DMY delivery system, which can be further applied as an active package. Full article

Porcine epidemic diarrhea virus (PEDV) has developed as a global problem for the pig business, resulting in significant financial losses. Black soldier fly extract (BFE) has been proven to improve intestinal growth in pigs after weaning. Consequently, the goal of the present investigation was to explore the effects of BFE supplementation on intestinal function in PEDV-infected piglets. Eighteen piglets were randomly allocated to three groups: control, PEDV, and BFE + PEDV. The piglets in the BFE + PEDV group received 500 mg/kg BW of BFE orally for seven days from day 4 to 10 of the study. On day 9 of the study, six pigs from each group received either clean saline or PEDV solution at a dosage of 10⁶ TCID₅₀ (50% tissue culture infectious dose) per pig. On day 11, samples of blood and intestine were taken for additional investigation. The results indicated a significant decrease in the average daily gain (ADG) of piglets infected with PEDV (p < 0.05). Additionally, PEDV infection led to an alteration of blood indexes and a reduction in plasma D-xylose concentration and villi height in the small intestine, while it increased plasma diamine oxidase activity and small intestinal crypt depth in piglets (p < 0.05). The PEDV infection significantly reduced antioxidant enzyme activity in plasma and the gut, including total superoxide dismutase and catalase, while increasing contents of oxidation-relevant products such as malondialdehyde and hydrogen peroxide in piglets. Moreover, PEDV infection increased the mRNA expression level of antiviral-related genes (p < 0.05). Nutritional supplementation with BFE improved intestinal histomorphological indicators and reduced oxidative stress produced by PEDV infection in piglets. Interestingly, BFE could significantly promote the mRNA expression level of antiviral-related genes in the ileum (p < 0.05). Overall, the preliminary results suggest that dietary BFE could improve intestinal function in piglets after PEDV infection. Currently, the findings put a spotlight on the role of BFE in the prevention and treatment of PED in piglets. Full article

The endo-β-1,4-xylanase glycosyl hydrolase (GH11) decomposes the backbone of xylan into xylooligosaccharides or xylose. These enzymes are important for industrial applications in the production of biofuel, feed, food, and value-added materials. β-D-xylopyranose (XYP, also known as β-D-xylose) is the fundamental unit of the substrate xylan, and understanding its recognition is fundamental for the initial steps of GH11’s molecular mechanism. However, little is known about the recognition of a single XYP molecule by GH11. In this study, the crystal structures of GH11 from Thermoanaerobacterium saccharolyticum (TsaGH11) complexed with an XYP molecule were determined at a resolution of 1.7–1.9 Å. The XYP molecule binds to subsite −2 of the substrate-binding cleft. The XYP molecule is mainly stabilized by a π–π interaction with the conserved Trp36 residue. The O2 and O3 atoms of XYP are stabilized by hydrogen bond interactions with the hydroxyl groups of Tyr96 and Tyr192. The conformation of the thumb domain of TsaGH11 does not play a critical role in XYP binding, and XYP binding induces a shift in the thumb domain of TsaGH11 toward the XYP molecule. A structural comparison of TsaGH11 with other GH11 xylanases revealed that the XYP molecule forms π–π stacking with the center between the phenyl and indoline ring of Trp36, whereas the XYP molecule unit from xylobiose or xylotetraose forms π–π stacking with the indoline of Trp36, which indicates that the binding modes of the substrate and XYP differ. These structural results provide a greater understanding of the recognition of XYP by the GH11 family. Full article

Microalgal biomass can be utilized for the production of value-added chemicals and fuels. Within this research, Chlorella vulgaris biomass left behind after the extraction of lipids and proteins was converted to valuable sugars, organic acids and furanic compounds via hydrolysis/dehydration using dilute aqueous sulfuric acid as a homogeneous catalyst. Under mild conditions, i.e., low temperature and low sulfuric acid concentration, the main products of hydrolysis/dehydration were monomeric sugars (glucose and xylose) and furanic compounds (HMF, furfural) while under more intense conditions (i.e., higher temperature and higher acid concentration), organic acids (propionic, formic, acetic, succinic, lactic, levulinic) were also produced either directly from sugar conversion or via intermediate furans. As a second valorization approach, the residual microalgal biomass was converted to value-added sugar alcohols (sorbitol, glycerol) via hydrogenation/hydrogenolysis reactions over metallic ruthenium catalysts supported on activated carbons (5%Ru/C). It was also shown that a low concentration of sulfuric acid facilitated the conversion of biomass to sugar alcohols by initiating the hydrolysis of carbohydrates to monomeric sugars. Overall, this work aims to propose valorization pathways for a rarely utilized residual biomass towards useful compounds utilized as platform chemicals and precursors for the production of a wide variety of solvents, polymers, fuels, food ingredients, pharmaceuticals and others. Full article

In this study, the α-glucosidase (maltase-glucoamylase: MGAM) and α-amylase inhibitory properties elicited by xylooligosaccharides (XOSs) prepared from dulse xylan were analysed as a potential mechanism to control postprandial hyperglycaemia for type-2 diabetes prevention and treatment. Xylan was purified from red alga dulse powder and used for enzymatic hydrolysis using Sucrase X to produce XOSs. Fractionation of XOSs produced xylobiose (X2), β-(1→3)-xylosyl xylobiose (DX3), xylotriose (X3), β-(1→3)-xylosyl-xylotriose (DX4), and a dulse XOS mixture with n ≥ 4 xylose units (DXM). The different fractions exhibited moderate MGAM (IC₅₀ = 11.41–23.44 mg/mL) and α-amylase (IC₅₀ = 18.07–53.04 mg/mL) inhibitory activity, which was lower than that of acarbose. Kinetics studies revealed that XOSs bound to the active site of carbohydrate digestive enzymes, limiting access to the substrate by competitive inhibition. A molecular docking analysis of XOSs with MGAM and α-amylase clearly showed moderate strength of interactions, both hydrogen bonds and non-bonded contacts, at the active site of the enzymes. Overall, XOSs from dulse could prevent postprandial hyperglycaemia as functional food by a usual and continuous consumption. Full article

Sugarcane bagasse (SCB) is an abundant agricultural waste, rich in cellulose and hemicellulose, that could be used as an ideal raw material for succinic acid (SA) production. A two-step chemical pretreatment, involving alkali extraction and alkaline hydrogen peroxide treatment, was utilized to treat SCB, followed by multi-enzyme hydrolysis to obtain a reducing sugar hydrolysate mainly composed of glucose and xylose. Optimization of the multi-enzyme hydrolysis of pretreated SCB resulted in a final reducing sugar concentration of 78.34 g/L. In order to enhance the bioconversion of SCB to SA and to reduce the production costs, the initial reducing sugar concentration, nitrogen source, and MgCO₃ content were further optimized. The results demonstrated that the inexpensive corn steep liquor powder (CSLP) could be utilized as an alternative nitrogen source to yeast extract for the production of SA; and the optimal concentrations of initial reducing sugar, CSLP, and MgCO₃ were 70 g/L, 18 g/L, and 60 g/L, respectively. When fed-batch fermentation was conducted in a 2 L stirred bioreactor, approximately 72.9 g/L of SA was produced, with a yield of 83.2% and a productivity of 1.40 g/L/h. The high SA concentration, yield, and productivity achieved in this study demonstrate the potential of SCB, an agricultural waste, as a viable alternative substrate for Actinobacillus succinogenes GXAS137 to produce SA. This lays a solid foundation for the resource utilization of agricultural waste and cost-effective industrial-scale production of SA in the future. Full article

Xylose is nowadays converted into xylitol, a popular special chemical sweetener. Xylitol can be used not only in the pharmaceutical and food industries, but also in cosmetics and synthetic resins because of its countless properties. Conventionally, xylitol is produced by slurry reactors operating in batch with dispersed or supported catalysts. Hydrogen is continuously fed to maintain a constant pressure. In this work, the kinetics of the reaction were investigated to find the optimal operating conditions to minimize the by-products obtained. Given the great performances shown by the new Ru/SiO₂ sol–gel derived catalyst in glucose hydrogenation, in this work the mentioned catalyst was tested in the hydrogenation of xylose to xylitol both in batch and in continuous production to prove its stability and activity. Full article