Search

The effects of Konjac mannan oligosaccharides (KMOS) on diphenoxylate-induced constipation in mice were investigated in the present study. After administration with KMOS at 1800 mg/kg·bw, the weight and number of black feces within 24 h, and the gastrointestinal transit ratio were distinctly increased by 96.8%, 156.5% and 45.3%, respectively. Furthermore, KMOS regulated the levels of enteric nervous system parameters, including motilin, somatostatin, substance P, acetyl cholinesterase, endothelin and vasoactive intestinal peptide. Additionally, KMOS could recover the characteristics of small intestine villi and inhibit the reduction of mucosal thickness. KMOS administration produced more short chain fatty acids and lactic acid compared with the control group. The availability of 5-hydroxytryptamine and the expression of serotonin transporter were ameliorated in the KMOS treatment groups. Collectively, these findings suggested that KMOS could be considered as a functional food material for regulating intestinal function and alleviating constipation.

β-1,3-1,4-Glucanases are a type of hydrolytic enzymes capable of catalyzing the strict cleavage of β-1,4 glycosidic bonds adjacent to β-1,3 linkages in β-D-glucans and have exhibited great potential in food and feed industrials. In this study, a novel glycoside hydrolase (GH) family 12 β-1,3-1,4-glucanase (CtGlu12A) from the thermophilic fungus Chaetomium sp. CQ31 was identified and biochemically characterized. CtGlu12A was most active at pH 7.5 and 65 °C, respectively, and exhibited a high specific activity of 999.9 U mg−1 towards lichenin. It maintained more than 80% of its initial activity in a wide pH range of 5.0–11.0, and up to 60 °C after incubation at 55 °C for 60 min. Moreover, the crystal structures of CtGlu12A with gentiobiose and tetrasccharide were resolved. CtGlu12A had a β-jellyroll fold, and performed retaining mechanism with two glutamic acids severing as the catalytic residues. In the complex structure, cellobiose molecule showed two binding modes, occupying subsites −2 to −1 and subsites + 1 to + 2, respectively. The concave cleft made mixed β-1,3-1,4-glucan substrates maintain a bent conformation to fit into the active site. Overall, this study is not only helpful for the understanding of the substrate-binding model and catalytic mechanism of GH 12 β-1,3-1,4-glucanases, but also provides a basis for further enzymatic engineering of β-1,3-1,4-glucanases.

An electrochemical biosensor was prepared for nucleic acid-based hantavirus detection using a Cu-based metal-organic framework (CuMOF) as a signal tag. The CuMOF was synthesized by the solvothermal method and then covalently bonded with signal DNA (sDNA) probes. The Au nanoparticles and reduced graphene oxide composite were deposited on the electrode surface by electroreduction as support substrate and was then functionalized with capture DNA (cDNA) probes by self-assembly. Through the complementary base pairing, the target DNA (tDNA) fragment of hantavirus hybridized with the cDNA and the sDNA in a sandwich-type format. The tDNA was detected according to the current signal of the CuMOF catalyzed reaction using o-phenylenediamine as redox substrate. The peak current of the biosensor at − 0.55 V increased linearly in proportion to the logarithmic value of the tDNA concentration from 10−15 to 10−9 mol/L, with a detection limit of 0.74 × 10−15 mol/L. Moreover, the proposed biosensor was successfully applied to detect hantavirus and was able to distinguish hantavirus from other arboviruses.

D-Mannose isomerase can reversibly catalyze D-fructose to D-mannose which has various beneficial effects. A novel D-mannose isomerase gene (PsMIaseA) from Pseudomonas syringae was cloned and expressed in Escherichia coli. The recombinant D-mannose isomerase (PsMIaseA) showed the highest amino acid sequence homogeneity of 50% with ManI from Thermobifda fusca. PsMIaseA was purified through Ni-NTA chromatography, and its specific activity was 818.6 U mg-1. The optimal pH and temperature of PsMIaseA were pH 7.5 and 45 °C, respectively. The enzyme was stable within a wide pH range from 5.0 to 10.0. It could efficiently convert D-fructose to D-mannose without any metal ions. When PsMIaseA was incubated with 600 g/L D-fructose for 6 h, the space-time yield of D-mannose reached 27.2 g L-1 h-1 with a maximum conversion ratio of 27%. Therefore, the D-mannose isomerase may be suitable for green production of D-mannose.

The problem of stochastic adaptive air-fuel ratio control by the dynamic model of biogas-fuelled engines is investigated in this paper. An adaptive law is employed to estimate the theoretical air-fuel ratio, which is undetermined due to the uncertainty of the methane concentration in the biogas. A stochastic adaptive air-fuel ratio controller in consideration of the stochasticity of the residual gas is designed based on the adaptive law, and the closed-loop system is proven to be mean-square stable. The proposed stochastic adaptive air-fuel ratio controller is validated through a numerical simulation when the theoretical air-fuel ratio is unknown constants and jump signals.

β-1,4-Mannanase degrades β-1,4-mannan polymers into manno-oligosaccharides with a low degree of polymerization. To date, only one glycoside hydrolase (GH) family 113 β-1,4-mannanase, from Alicyclobacillus acidocaldarius (AaManA), has been structurally characterized, and no complex structure of enzyme–manno-oligosaccharides from this family has been reported. Here, crystal structures of a GH family 113 β-1,4-mannanase from Amphibacillus xylanus (AxMan113A) and its complexes with mannobiose, mannotriose, mannopentaose, and mannahexaose were solved. AxMan113A had higher affinity for −1 and +1 mannoses, which explains why the enzyme can hydrolyze mannobiose. At least six subsites (−4 to +2) exist in the groove, but mannose units preferentially occupied subsites −4 to −1 because of steric hindrance formed by Lys-238 and Trp-239. Based on the structural information and bioinformatics, rational design was implemented to enhance hydrolysis activity. Enzyme activity of AxMan113A mutants V139C, N237W, K238A, and W239Y was improved by 93.7, 63.4, 112.9, and 36.4%, respectively, compared with the WT. In addition, previously unreported surface-binding sites were observed. Site-directed mutagenesis studies and kinetic data indicated that key residues near the surface sites play important roles in substrate binding and recognition. These first GH family 113 β-1,4-mannanase–manno-oligosaccharide complex structures may be useful in further studying the catalytic mechanism of GH family 113 members, and provide novel insight into protein engineering of GHs to improve their hydrolysis activity.

Mannan is one of the major constituent groups of hemicellulose, which is a renewable resource from higher plants. β-Mannanases are enzymes capable of degrading lignocellulosic biomass. Here, an endo-β-mannanase from Rhizopus microsporus (RmMan134A) was cloned and expressed. The recombinant RmMan134A showed maximal activity at pH 5.0 and 50 °C, and exhibited high specific activity towards locust bean gum (2337 U/mg). To gain insight into the substrate-binding mechanism of RmMan134A, four complex structures (RmMan134A–M3, RmMan134A-M4, RmMan134A-M5 and RmMan134A-M6) were further solved. These structures showed that there were at least seven subsites (−3 to +4) in the catalytic groove of RmMan134A. Mannose in the −1 subsite hydrogen bonded with His113 and Tyr131, revealing a unique conformation. Lys48 and Val159 formed steric hindrance, which impedes to bond with galactose branches. In addition, the various binding modes of RmMan134A–M5 indicated that subsites −2 to +2 are indispensable during the hydrolytic process. The structure of RmMan134A–M4 showed that mannotetrose only binds at subsites +1 to +4, and RmMan134A could therefore not hydrolyze mannan oligosaccharides with degree of polymerization ≤4. Through rational design, the specific activity and optimal conditions of RmMan134A were significantly improved. The purpose of this paper is to investigate the structure and function of fungal GH family 134 β-1,4-mannanases, and substrate-binding mechanism of GH family 134 members.

An engineered β-mannanase (mRmMan5A) from Rhizomucor miehei was successfully expressed in Pichia pastoris. Through high cell density fermentation, the expression level of mRmMan5A reached 79,680 U mL−1. The mRmMan5A showed maximum activity at pH 4.5 and 65 °C, and exhibited high specific activities towards mannans. To produce manno-oligosaccharides, palm kernel cake (PKC) was pretreated by steam explosion at 200 °C for 7.5 min, and then hydrolyzed by mRmMan5A. As a result, the total manno-oligosaccharide yield reached 34.8 g/100 g dry PKC, indicating that 80.6% of total mannan in PKC was hydrolyzed. Moreover, the kilo-scale production of manno-oligosaccharides was carried out to verify the feasibility of mass production. A total of 261.3 g manno-oligosaccharides were produced from 1.0 kg of dry PKC. An effective β-mannanase for the bioconversion of mannan-rich biomasses and an efficient method for the production of manno-oligosaccharides from PKC are provided in this paper.

Partially hydrolyzed guar gum (PHGG), an important supplemental dietary fiber, has been used as food ingredient in many industries. In this study, a novel β-mannanase gene (RmMan5A) from Rhizomucor miehei was successfully expressed in Pichia pastoris and subjected for PHGG production. Enzyme activity of fermentation supernatant reached 85,200UmL-1 after 168h high cell density fermentation. The purified RmMan5A exhibited the highest enzyme activity at pH 7.0 and 65°C. RmMan5A was then employed for guar gum hydrolysis and PHGG obtained demonstrated a weight-average molecular weight (Mw) of 2.5×104Da. Total dietary fiber accounted 90.6% of PHGG and 24.9% (w/w) of PHGG were identified as manno-oligosaccharides with degree of polymerization

The crystallization behavior and microstructure of a series of Dy 3 + /Tb 3 + doped aluminoborosilicate (ABS) magneto-optical glass was investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The apparent crystallization activation energy ( E g ) and the kinetic properties at the corresponding glass transition temperature ( T g ) were studied as a function of Dy 3 + /Tb 3 + concentration. The results showed that the glass matrix precipitated Al 3 Tb(BO 3 ) 4 and TbBO 3 crystals when subjected to heat treatment at 852.8 and 902.6 °C, respectively. The crystallization activation energy of these two crystalline phases (Al 3 Tb(BO 3 ) 4 and TbBO 3 ) was E p1 = 993.3 kJ/mol and E p2 = 544.97 kJ/mol, respectively. The average crystallization index was 0.5 and 0.8, respectively. By applying the Kissinger equation to the parameterized crystallization behavior, the calculated phase transition activation energy was determined to be 420.18 kJ/mol. The parameterized crystallization behavior of this particular ABS magneto-optical glass can be used to avoid the deterioration of magneto-optical properties due to the crystallization of glass matrix.

Background β-Mannanase randomly cleaves the β-1,4-linked mannan backbone of hemicellulose, which plays the most important role in the enzymatic degradation of mannan. Although the industrial applications of β-mannanase have tremendously expanded in recent years, the wild-type β-mannanases are still defective for some industries. The glycoside hydrolase (GH) family 5 β-mannanase (RmMan5A) from Rhizomucor miehei shows many outstanding properties, such as high specific activity and hydrolysis property. However, owing to the low catalytic activity in acidic and thermophilic conditions, the application of RmMan5A to the biorefinery of mannan biomasses is severely limited. Results To overcome the limitation, RmMan5A was successfully engineered by directed evolution. Through two rounds of screening, a mutated β-mannanase (mRmMan5A) with high catalytic activity in acidic and thermophilic conditions was obtained, and then characterized. The mutant displayed maximal activity at pH 4.5 and 65 °C, corresponding to acidic shift of 2.5 units in optimal pH and increase by 10 °C in optimal temperature. The catalytic efficiencies (k cat/K m) of mRmMan5A towards many mannan substrates were enhanced more than threefold in acidic and thermophilic conditions. Meanwhile, the high specific activity and excellent hydrolysis property of RmMan5A were inherited by the mutant mRmMan5A after directed evolution. According to the result of sequence analysis, three amino acid residues were substituted in mRmMan5A, namely Tyr233His, Lys264Met, and Asn343Ser. To identify the function of each substitution, four site-directed mutations (Tyr233His, Lys264Met, Asn343Ser, and Tyr233His/Lys264Met) were subsequently generated, and the substitutions at Tyr233 and Lys264 were found to be the main reason for the changes of mRmMan5A. Conclusions Through directed evolution of RmMan5A, two key amino acid residues that controlled its catalytic efficiency under acidic and thermophilic conditions were identified. Information about the structure–function relationship of GH family 5 β-mannanase was acquired, which could be used for modifying β-mannanases to enhance the feasibility in industrial application, especially in biorefinery process. This is the first report on a β-mannanase from zygomycete engineered by directed evolution. Electronic supplementary material The online version of this article (doi:10.1186/s13068-017-0833-x) contains supplementary material, which is available to authorized users.

Functional oligosaccharides, particularly konjac mannan oligosaccharides (KMOS), can regulate glucose metabolism. However, the molecular mechanisms involved in the hypoglycemic effect of KMOS remain largely unknown. Here, the effect of KMOS supplementation on glucose homeostasis was evaluated in both high-fat diet (HFD)-fed C57BL/6J mice and high-glucosamine-induced HepG2 cells. KMOS supplementation remarkably ameliorated the fasting blood glucose, glucose tolerance, and insulin tolerance of HFD-fed mice. Abnormalities of triglyceride and glycogen metabolism in the liver induced by the HFD were reversed by KMOS supplementation. The insulin signaling pathway was activated by KMOS, with stimulation of GLUT2 membrane translocation and glucose uptake in HepG2 cells via the AMPK pathway. Moreover, KMOS suppressed p-mTOR expression and stimulated the GSK-3&beta, /CREB pathway via the AMPK pathway. KMOS significantly upregulated leptin receptor expression and downregulated PTP1B and SOCS3 levels in the liver and brain, with a decreased serum leptin concentration. Phosphorylation of JAK2 and STAT3 in the liver was activated by KMOS supplementation, while the expressions of Sirt1, Tfam, and Pgc1-&alpha, in the brain were elevated. Conclusively, KMOS attenuated HFD-induced glucose metabolism dysfunction through the regulation of insulin resistance and leptin resistance. This finding indicates that KMOS have potential value as an anti-hyperglycemic dietary supplement.

To produce manno-oligosaccharides from cassia gum, a mutated glycoside hydrolase family 134 β-mannanase gene (mRmMan134A) from Rhizopus microsporus var. rhizopodiformis F518 was expressed in Pichia pastoris and a high expression level (3680 U mL−1) was obtained through high cell density fermentation. mRmMan134A exhibited maximum activity at pH 5.5 and 50 °C. It was then subjected to hydrolyze cassia gum with 70.6% of overall yield of manno-oligosaccharides. From the hydrolysate, seven components (F1–F7) were separated and identified as mannose, mannobiose, galactose, mannotriose, mannotetraose, 61-α- d -galactosyl-β- d -mannobiose, and mannopentaose, respectively. According to in vitro fermentation, the manno-oligosaccharides were able to promote the growth of three Bifidobacterium strains and six Lactobaillus strains with 3.0-fold increment in culture absorbance, and these strains preferred manno-oligosaccharides with degree of polymerization (DP) 2–3 rather than those with DP 4–5. Novel manno-oligosaccharides from cassia gum with promising prebiotic activity were provided in the present study.

Natural polysaccharides, particularly galactomannans, are potential candidates for treatment of alcoholic liver diseases (ALD). However, applications are restricted due to the physicochemical properties associated with the high molecular weight. In this work, guar gum galactomannans were partially hydrolyzed by &beta, mannanase, and the molecular mechanisms of hepatoprotective effects were elucidated both in vitro and in vivo. Release of lactate dehydrogenase and cytochrome C were attenuated by partially hydrolyzed guar gum (PHGG) in HepG2 cells, due to protected cell and mitochondrial membrane integrity. PHGG co-administration decreased serum amino transaminases and cholinesterase levels of acute alcohol intoxicated mice, while hepatic pathologic morphology was depleted. Activity of superoxide dismutase, catalase, and glutathione peroxidase was recovered to 198.2, 34.5, 236.0 U/mg protein, respectively, while malondialdehyde level was decreased by 76.3% (PHGG, 1000 mg/kg∙day). Co-administration of PHGG induced a 4.4-fold increment of p-AMPK expression, and lipid metabolism was mediated. PHGG alleviated toll-like-receptor-4-mediated inflammation via the signaling cascade of MyD88 and I&kappa, B&alpha, decreasing cytokine production. Moreover, mediated expression of Bcl-2 and Bax was responsible for inhibited acute alcohol-induced apoptosis with suppressed cleavage of caspase 3 and PARP. Findings gained suggest that PHGG can be used as functional food supplement for the treatment of acute alcohol-induced liver injury.

A novel glycoside hydrolase family 5 β-mannosidase gene (AcMan5) from the filamentous fungus Absidia corymbifera D1 was cloned and expressed in Escherichia coli. AcMan5 had an open reading frame of 1311 bp encoding 436 amino acids. The β-mannosidase (AcMan5) shared highest amino acid sequence identity (73%) with the β-mannosidase from Rhizomucor miehei. The purified β-mannosidase was a monomer of 51.9 kDa. Its optimal pH and temperature were pH 5.5 and 60 °C, respectively. The enzyme was stable up to 60 °C and within a pH range of 4.0⿿10.5. It was found to be a typical exo-β-mannosidase acting on the non-reducing end of manno-oligosaccharides. In addition, AcMan5 displayed high transglycosylation activity. It could transfer mannose residue to six acceptors ⿿ glucose, galactose, fructose, gentiobiose, laminaribiose and sucrose ⿿ among 20 candidates at low donor concentration in a short time. Due to its hydrolytic and transglycosylation properties, AcMan5 may have potential in several industrial applications. This is the first report on a β-mannosidase from Absidia species.

Foam glass was prepared which using iron tailings and waste glass with SiC powders as foaming agent. The influence of the foam temperature on the bulk density, porosity, water absorption and compressive strength was studied. The results show that foam glass with higher iron tailings content of 24.5 wt% could be prepared at about 830 °C for 30 min. Some of the reactions inside the iron tailings are responsible for the foaming mechanisms. When the foam temperature was 830 °C, the bulk density and flexural strength reached a minimum value of 0.224 g/cm 3 and 0.53 MPa.

Due to high operating cost, limited coverage range, complex installation and additional weight, helicopter and other general aviation aircraft may not have datalink function implemented as portion of its avionics system. However, datalink has great advantages of releasing crowed VHF channel resources, reducing pilot and controller workload, supporting automation application, gaining time efficiency and operation precision. During the preflight, in-the-air and post-flight periods, general aviation operators and ground stations always demand data from helicopters, similar to Airline Operation Control (AOC) for air transportation. The automotive control trends and mandatory standards also drive the installation of data communication for the helicopters. By using SysML modeling language, this paper tries to identify the data link communication scenarios and requirements for helicopters. The feasibility of utilizing existing high speed mobile network for helicopters data communication is analyzed and confirmed, which removes the cost obstacles of helicopter datalink applications. Based on the operational concept and requirement analysis, flexible and scalable datalink system architecture for helicopters is proposed, which support both the VHF ACARS and mobile cellular network. Since the weight and size of airborne system for helicopter is severely restricted, besides the data communication radios, all the other router, protocol stacks and applications should be hosted in the modular computing resources and/or multi-function displays. With an integrated data communication radio and the datalink partition hosted applications, the airborne datalink system can support the 4G/LTE, WiFi, VHF ACARS and other future new communication channels, e.g. broadband satellite communication and AeroMACS system etc.