D-Mannose/D-Fructose/D-Glucose Assay kit

Both β-mannanases and β-mannosidases are required for mannan-backbone degradation into mannose. In this study, two β-mannosidases of glycoside hydrolase (GH) families 2 (BtMan2A) and 5 (CmMan5A) were evaluated for their substrate specificities and galactomannan binding ability. BtMan2A preferred short manno-oligomers, while CmMan5A preferred longer ones; DP >2, and galactomannans. BtMan2A displayed irreversible galactomannan binding, which was pH-dependent, with higher binding observed at low pH, while CmMan5A had limited binding. Docking and molecular dynamics (MD) simulations showed that BtMan2A galactomannan binding was stronger under acidic conditions (-8.4 kcal/mol) than in a neutral environment (-7.6 kcal/mol), and the galactomannan ligand was more unstable under neutral conditions than acidic conditions. Qualitative surface plasmon resonance (SPR) experimentally confirmed the reduced binding capacity of BtMan2A at pH 7. Finally, synergistic β-mannanase to β-mannosidase (BtMan2A or CmMan5A) ratios required for maximal galactomannan hydrolysis were determined. All CcManA to CmMan5A combinations were synergistic (≈1.2-fold), while combinations of CcManA with BtMan2A (≈1.0-fold) yielded no hydrolysis improvement. In conclusion, the low specific activity of BtMan2A towards long and galactose-containing oligomers and its non-catalytic galactomannan binding ability led to no synergy with the mannanase, making GH2 mannosidases ineffective for use in cocktails for mannan degradation.

Premature skin aging occurs due to the increased formation of reactive oxygen species (ROS), which causes oxidative stress, DNA damage, and collagen degradation. This study investigates the protective effect of Scenedesmus dimorphus polysaccharides (SDP) as an antioxidant and anti-aging agent on an aging rat model induced by D-galactose (D-gal). This study used 48 male Wistar rats divided into six groups: (1) normal control, (2) polysaccharide control, (3) aging control induced by D-gal 0.25 mg/g bw/days, (4) drug control (vitamin E) treated twice with SDP in an aging rat model, (5) D-gal + SDP (0.2 mg/g bw), and (6) D-gal + SDP (0.8 mg/g bw) treated with oral treatment and observed for periods of 2, 4, and 8 weeks. Giving SDP at a dose of 0.8 mg/g bw can increase superoxide dismutases and catalase activity and reduce malondialdehyde after 8 weeks of observation, which is better than giving vitamin E. The treatment of SDP can stimulate collagen synthesis and reduce advanced glycation end products. Histopathology shows an increase in the area of fibrocollagen proportions and deposition from the matrix on giving SDP, which is better than vitamin E, since SDP can repair skin tissue. Thus, SDP can be useful as an antioxidant and anti-aging agent in an aging Wistar rats model.

Yeast and microalgae are microorganisms with widely diverging physiological and biotechnological properties. Accordingly, their fields of applications diverge: yeasts are primarily applied in processes related to fermentation, while microalgae are used for the production of high-value metabolites and green technologies such as carbon capture. Heterotrophic–autotrophic systems and synthetic ecology approaches have been proposed as tools to achieve stable combinations of such evolutionarily unrelated species. We describe an entirely novel synthetic ecology-based approach to evolve co-operative behaviour between winery wastewater isolates of the yeast Saccharomyces cerevisiae and microalga Chlorella sorokiniana. The data show that biomass production and mutualistic growth improved when co-evolved yeast and microalgae strains were paired together. Combinations of co-evolved strains displayed a range of phenotypes, including differences in amino acid profiles. Taken together, the results demonstrate that biotic selection pressures can lead to improved mutualistic growth phenotypes over relatively short time periods.

Pythium insidiosum is an oomycete that affects mammals, especially humans and horses, causing a difficult-to-treat disease. Typically, surgical interventions associated with antimicrobial therapy, immunotherapy, or both are the preferred treatment choices. PitiumVac^® is a therapeutic vaccine prepared from the mycelial mass of P. insidiosum and is used to treat Brazilian equine pythiosis. To better understand how PitiumVac^® works, we analyzed the composition of PitiumVac^® and the immune response triggered by this immunotherapy in mice. We performed an enzymatic quantification that showed a total glucan content of 21.05% ± 0.94 (α-glucan, 6.37% ± 0.77 and (1,3)(1,6)-β-glucan, 14.68% ± 0.60) and mannose content of 1.39% ± 0.26; the protein content was 0.52 mg ml⁻¹ ± 0.07 mg ml⁻¹. Healthy Swiss mice (n = 3) were subcutaneously preimmunized with one, two, or three shots of PitiumVac^®, and immunization promoted a relevant Th1 and Th17 responses compared to nonimmunization of mice. The highest cytokine levels were observed after the third immunization, principally for IFN-γ, IL-17A, IL-6, and IL-10 levels. Results of infected untreated (Pythiosis) and infected treated (Pythiosis + PVAC) mice (n = 3) showed that PitiumVac^® reinforces the Th1/Th17 response displayed by untreated mice. The (1,3)(1,6)-β-glucan content can be, at least in part, related to this Th1/Th17 response.

An effective and ecological method for liberation of pectin-derived oligosaccharides (POS) from sugar beet pulp (SBP) was developed using enzymatic and microorganism-mediated biomass conversion. The POS may be applied in the production of prebiotic feed additives. Various yeast strains were screened for their capacity for protein synthesis and monosaccharide assimilation. Combined yeast cultivation and pectin hydrolysis were found to be an effective method of producing prebiotics. Separate enzymatic hydrolysis and fermentation of SBP resulted in the release of 3.6 g of POS per 100 g d.w., whereas the yield of POS acquired after the combined process was 17.9% higher, giving 4.2 g of POS per 100 g d.w. Introducing the yeast into the process improved hydrolysis performance due to lower enzyme inhibition by mono- and disaccharides. The prebiotic effect of the POS was assessed by in vitro fermentation using individual cultures of gastrointestinal bacteria. The POS in the SBP hydrolysate effectively promoted the growth of lactobacilli and bifidobacteria. A large increase in adherence to Caco-2 cells in the presence of POS was noted for beneficial Lactobacillus brevis strains, whereas pathogenic bacteria and yeast (C. albicans, C. lusitanie, C. pelliculosa), responsible for infections in breeding animals, showed much weaker adhesion.

The chemical characteristics of lysates obtained from yeasts belonging to Metschnikowia spp. were determined. Cell lysis was induced using saponin from Q. saponaria or 5% NaCl. The process was conducted at 50°C for 24 for 48 h. The enzymatic profiles of the resulting lysates were analyzed. The mannose and glucose contents were also investigated, as well as the concentrations of proteins, free amino nitrogen (FAN), and free amino acids. The results were compared to the characteristics of lysates from conventional industrial strains of Saccharomyces spp. obtained under analogous conditions. The Metschnikowia lysates showed different chemical profiles and the pool of individual amino acids was generally smaller. However, the content of hydroxyproline HPro was 4 to 5 times higher. The results of this study show that yeast lysates are an attractive supplement for numerous applications.

The potential of PEF for accelerating the release of mannoproteins from Saccharomyces cerevisiae yeast during aging on lees of Caladoc red wine was evaluated. The release of mannoproteins increased rapidly in red wine samples containing PEF-treated yeasts in comparison to samples containing untreated yeast. While one month of aging on lees was required to obtain the highest mannoprotein concentration in wines containing PEF-treated yeast, the same amount of mannoproteins was obtained after three months in the wine-containing untreated yeast. It was demonstrated that PEF treatment promoted the liberation of enzymes involved in the release of mannoproteins from the cell wall of yeast during autolysis such as β-glucanase and protease. The functional properties of mannoproteins released from PEF-treated yeast were similar to that of those released from untreated yeast. Mannoproteins reduced wine astringency. Sensorial analysis confirmed that panelists did not find differences in astringency when wine aged on lees for 1 month with PEF-treated yeast was compared with wine aged on lees for 3 months with untreated yeast. Therefore, PEF represents a potential technique for reducing the duration of aging on lees in red winemaking.

In this paper, lemon and fennel wastes were recovered and used as secondary-raw polysaccharide sources. These polysaccharides were exploited as natural plasticizers of sodium alginate (A) based films, in order to improve sodium alginate performances, limited by its fragility, extending its potential application in a cost effective and eco-friendly way. Different green processes, such as maceration (MAC), ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), were carried out for obtaining high yield of lemon and fennel polysaccharides (LP and FP). Actually, HPAE-PAD and TLC analyses evidenced the presence of xyslose, galactose, glucose and rhamnose monomers and galacturonic acid, typical of polysaccharides like pectin and xyloglucan chains. These findings were confirmed by NMR and FTIR spectroscopic analyses. Moreovers, gel filtration chromatography assessed the high molecular weight of recovered polysaccharides, particularly of FP waste fraction. The extracted polysaccharides were used as eco-friendly and cost-effective plasticizers of sodium alginate films (AFP and ALP). DSC analysis evidenced a significant decreasing of glass transition temperature of the polymer, tensile tests showed an enlightened rising of elongation at break and TGA analysis showed a faster degradation kinetics of AFP and ALP films, as expected in a plasticized system.

A diluted alkali-soluble pectin (DASP) fraction, extracted using sodium carbonate, is characterized by a low degree of methylesterification and has the ability to self-organize on mica. The aim of this study was to characterize the cross-linking process of this fraction, extracted from apples, over a wide pH range (3-11) and without the addition of salt. An FT-IR study showed an increase in the intensity of bands connected with ν_as and ν_s (COO⁻) and a decrease in the intensity of the band associated with ν (C=O) in the carboxyl group with increasing pH, which indicated the dissociation of the carboxyl groups of galacturonic acid units. An increase in the surface electrical charge of particles in the pH range of 3-7 confirmed this. The value of the average apparent dissociation constant (∼4.60) indicated the acidic character of the DASP fraction. An AFM study showed the morphological changes of the DASP fraction with increasing pH, which allowed for the evaluation of the cross-linking process. This fraction formed a network on mica at pH 4 and 9, while the aggregates were noted mainly at pH 11. For totally ionized carboxyl groups (pH 7), the pectin chains were separated from each other due to the electrostatic repulsion between them.

Glycans are major nutrients available to the human gut microbiota (HGM). The Bacteroides are generalist glycan degraders and this function is mediated largely by polysaccharide utilization loci (PULs). The genomes of several Bacteroides species contain a PUL, PUL1,6-beta;-glucan, that was predicted to target mixed linked plant 1,3;1,4-beta-glucans. To test this hypothesis we characterized the proteins encoded by this locus in Bacteroides thetaiotaomicron, a member of the HGM. We show here that PUL1,6-β-glucan does not orchestrate the degradation of a plant polysaccharide but targets a fungal cell wall glycan, 1,6-beta-glucan, which is a growth substrate for the bacterium. The locus is upregulated by 1,6-beta-glucan, and encodes two enzymes, a surface endo-1,6-beta-glucanase, BT3312, and a periplasmic beta-glucosidase that targets primarily 1,6-beta-glucans. The non-catalytic proteins encoded by PUL1,6-beta-glucan target 1,6-beta-glucans and comprise a surface glycan binding protein and a SusD homologue that delivers glycans to the outer membrane transporter. We identified the central role of the endo-1,6-beta-glucanase in 1,6-beta-glucan depolymerization by deleting bt3312, which prevented the growth of B. thetaiotaomicron on 1,6-beta-glucan. The crystal structure of BT3312 in complex with β-glucosyl-1,6-deoxynojirimycin, revealed a TIM barrel catalytic domain that contains a deep substrate binding cleft tailored to accommodate the hook-like structure adopted by 1,6-beta-glucan. Specificity is driven by the complementarity of the enzyme active site cleft and the conformation of the substrate. We also noted that PUL1,6-beta-glucan is syntenic to many PULs from other Bacteroidetes suggesting that utilization of yeast and fungal cell wall 1,6-beta-glucans is a widespread adaptation within the human microbiota.

Almond shell is a major waste from the almond processing industry. Its feasibility as natural source of health-promoting components was examined. The by-product was fractionated under basic conditions following an easy scale-up process. The chemical composition of the recovered fraction and its antioxidant and antidiabetic properties were evaluated. Novel information regarding the chemical composition of the polysaccharides was also obtained. Almond shell is formed by lignin-carbohydrate complexes possessing antioxidant properties and capacity to inhibit α-glucosidase. According to our knowledge, this is the first time α-glucosidase inhibitory activity of a lignin-carbohydrate complex is reported. Biscuits containing non-caloric sweetener soluble (2.5%) and insoluble (5.6%) dietary fiber, natural antioxidants (1.34 mg of gallic acid equivalents/g) and α-glucosidase inhibitors (1 g of biscuit–1 mg of acarbose) achieved a high sensorial score (7.2 out of 9) when almond shell was incorporated to them. The application of a fraction from almond shell containing lignin-polysaccharides complexes as food ingredient in biscuit formulations for people with particular nutritional requirements is feasible and new.

Smith, B. D. & Divol, B. (2017). Food Microbiology, 73, 39-48.

This paper presents the results of a study to determine the effect of Quillaja saponaria saponins on the lysis of industrial yeast strains. Cell lysis induced by saponin from Q. saponaria combined with the plasmolysing effect of 5% NaCl for Saccharomyces cerevisiae, Kluyveromyces marxianus yeasts biomass was conducted at 50 °C for 24-48 h. Membrane permeability and integrity of the yeast cells were monitored using fluorescent techniques and concentrations of proteins, free amino nitrogen (FAN) and free amino acids in resulting lysates were analyzed. Protein release was significantly higher in the case of yeast cell lysis promoted with 0.008% Q. saponaria and 5% NaCl in comparison to plasmolysis triggered by NaCl only.

Cost-effective application of lignocellulolytic enzymes holds the key towards commercialization of enzymatic hydrolysis of lignocellulosic biomass. Carrier free immobilization of enzyme(s) offers a lucrative prospect. Combined-cross linked enzyme aggregates (combi-CLEAs) are a novel prospective and this present study addresses the preparation, characterization and application of xylanase-mannanase combi-CLEAS on lime-preteated sugarcane bagasse and milled corn stover. X6-CLEAs, X7-CLEAs, L1-CLEAs and L7-CLEAs were prepared after elaborative optimization of the precipitating agent and glutaraldehyde concentration. The highest activity after precipitation was observed with acetone but following cross-linking with glutaraldehyde less than 60% activity was retained, while more than 60% activity was retained after precipitation with ammonium sulphate and cross-linking with glutaraldehyde. Accessory enzyme activities including α-arabinofuranosidase, β-xylosidase, esterases, β-mannosidase, α-galactosidase and β-glucosidase were also determined. More than an 1.5 fold increase in thermostability compared to the free enzyme was observed over a broad temperature range (50-70°C). Tri-synergy studies and quad synergy studies were used to generate combi-CLEAs with different protein ratios. Hydrolysis of lime pre-treated bagasse with combi-CLEAs at protein ratios corresponding to X6 (33.0%):X7 (17.0%):L1 (17.0%):L7 (33.0%) resulted in a 1.68 fold higher sugar release compared to the quad synergy model using free enzymes. Similarly, hydrolysis of corn stover with combi-CLEAs at protein ratios corresponding to X6 (40.0%):X7 (10.0%):L1 (10.0%):L7 (40.0%) resulted in an 1.58 fold higher sugar release compared to the sugar release observed with the quad synergy model using free enzymes. Monomeric sugars constituted 70-75% of reducing sugars released during hydrolysis. The role of accessory enzymes in improving enzyme synergy was clearly shown. The efficiency of combi-CLEAs compared to free enzymes makes them ideal candidates for the prudent and cost-effective commercialization of lignocellulolytic enzymes.

A mannosylglycerate synthase (MgS) gene detected in the genome of Selaginella moellendorffii was expressed in E. coli and the recombinant enzyme was purified and characterized. A remarkable and unprecedented feature of this enzyme was the ability to efficiently synthesize mannosylglycerate (MG) and glucosylglycerate (GG) alike, with maximal activity at 50°C, pH 8.0 and with Mg²⁺ as reaction enhancer. We have also identified a novel glycoside hydrolase gene in this plant’s genome, which was functionally confirmed to be highly specific for the hydrolysis of MG and GG and named MG hydrolase (MgH), due to its homology with bacterial MgHs. The recombinant enzyme was maximally active at 40°C and at pH 6.0–6.5. The activity was independent of cations, but Mn²⁺ was a strong stimulator. Regardless of these efficient enzymatic resources we could not detect MG or GG in S. moellendorffii or in the extracts of five additional Selaginella species. Herein, we describe the properties of the first eukaryotic enzymes for the synthesis and hydrolysis of the compatible solutes, MG and GG.

The accumulation patterns and biosynthesis of compatible solutes in hyper/thermophiles have been extensively studied. However, there is little information available on their hydrolysis, leading us to search for enzymes for this activity. From the analysis of the genomes of several microorganisms known to accumulate α-D-mannopyranosyl-(1 → 2)-D-glycerate (mannosylglycerate, MG) or α-D-glucopyranosyl-(1 → 2)-D-glycerate (glucosylglycerate, GG) we were able to identify a likely candidate gene for the hydrolysis of these molecules. The Thermus thermophilus HB27 homologue encoded a putative enzyme with motifs of the GH63 and GH37 families of glycoside hydrolases. We expressed the gene from this thermophilic bacterium and from Rubrobacter radiotolerans, and confirmed that the recombinant enzymes, here designated mannosylglycerate hydrolase (MgH), specifically hydrolysed MG (or GG) to mannose (or glucose) and glycerate. Both enzymes were highly stable and maximally active at temperatures close to each organisms’ optimal growth temperatures (half-lives of 15.4 ± 0.5 h at 55°C and 16.1 ± 0.4 h at 70°C) but at low pH (4.0–4.5). Cations were not required for their activity and each enzyme exhibited Michaelis–Menten kinetics at 50°C and 70°C, respectively, with comparable catalytic efficiencies towards MG and GG. Herein, we purified and characterized a novel and highly specific MG- and GG-hydrolyzing enzyme that represent an attractive tool for development of enzymatic assays for quantification of these solutes, which seem to be more prevalent in microorganisms than initially suspected.

α-Mannosidases, important enzymes in the N-glycan processing and degradation in Eukaryotes, are frequently found in the genome of Bacteria and Archaea in which their function is still largely unknown. The α-mannosidase from the hyperthermophilic Crenarchaeon Sulfolobus solfataricus has been identified and purified from cellular extracts and its gene has been cloned and expressed in Escherichia coli. The gene, belonging to retaining GH38 mannosidases of the carbohydrate active enzyme classification, is abundantly expressed in this Archaeon. The purified α-mannosidase activity depends on a single Zn²⁺ ion per subunit is inhibited by swainsonine with an IC₅₀ of 0.2 mM. The molecular characterization of the native and recombinant enzyme, named Ssα-man, showed that it is highly specific for α-mannosides and α(1,2), α(1,3), and α(1,6)-D-mannobioses. In addition, the enzyme is able to demannosylate Man₃GlcNAc₂ and Man₇GlcNAc₂ oligosaccharides commonly found in N-glycosylated proteins. More interestingly, Ssα-man removes mannose residues from the glycosidic moiety of the bovine pancreatic ribonuclease B, suggesting that it could process mannosylated proteins also in vivo. This is the first evidence that archaeal glycosidases are involved in the direct modification of glycoproteins.

The effects of vapor pressure deficit (VPD) on litchi fruit quality have not yet been fully defined. The aim of this study was to detail the changes in physiology, sugars, organic acids, and individual anthocyanin concentrations in imported litchi fruit held at various controlled relative humidity (RH) and VPD levels. SO₂-fumigated (but not acid-treated) litchi imported from Thailand (cv. Kom) and from Israel (cv. Mauritius) were air freighted to the United Kingdom and then stored for 9 days at either 5 or 13°C to simulate shelf-life conditions. Fruits were stored under a series of controlled RH conditions for the duration of the trial using different concentrations of glycerol in deonized water. Respiration rates and weight losses of both fruit lots were greater in litchi stored at 13°C and a VPD of 0.274 kPa. At 5°C and a VPD of 0 or 0.042 kPa, sugars and organic acids in aril and pericarp tissue and individual anthocyanins in pericarp were better maintained. This is the first piece of work that has systematically evaluated the effect of a series of VPDs on litchi fruit biochemistry such that implications for designing systems to better maintain the physiological quality of imported litchi fruit are discussed.