Preparation and characterization of guluronic acid oligosaccharides degraded by a rapid microwave irradiation method

Molecular Engineering of Alginate Lyases and the Potential Agricultural Applications of Their Enzymatic Products

Alginate lyases, enzymes that degrade alginate into unsaturated oligosaccharides, have attracted significant attention for their potential applications across various fields, particularly in agriculture. This review focuses on the molecular engineering of alginate lyases to enhance their activity, stability, and specificity as well as the agricultural applications of the resulting enzymatic products, known as alginate oligosaccharides (AOS). We start by summarizing the sources and classification of alginate lyases, followed by recent advances in their engineering through directed evolution, rational design, truncation of noncatalytic domains, and conserved domain reconstruction. We then explore the diverse agricultural applications of AOS, including their ability to promote plant growth, to increase the content of active plant components, to extend fruit shelf life, and to enhance plant resistance to abiotic stresses. Furthermore, the potential value of AOS as feed additives and preservatives in shrimp-based products is also assessed. This review will not only lay a solid theoretical foundation but also serve as a catalyst for the innovative development and practical application of high-value enzymatic preparations and utilization of AOS-related products, providing new solutions for sustainable agriculture and the food industry.

Eco-friendly ozonation of alginate: Physicochemical characterization and degradation mechanism exploration through mass spectrometry

The ozone degradation has been proven to be an effective degradation method for alginate, while the degradation mechanism remained to be unconfirmed. In this study, two high-molecular-weight alginates with different mannuronic/guluronic (G/M) ratios, HM and HG (G/M 0.49 vs 1.40), were depolymerized using established ozonation technology platform. Notably, HM can be degraded faster than HG especially within initial 30 min, indicating that the β-1, 4-mannuronic bonds are more susceptible to be ozonated than α-1, 4-guluronic bonds. However, HM/HG degraded to LMWA in 2 h and reached a plateau. Therefore, we employed mass spectrometry (MS) to profile the degraded products of LMWA polymannuronate (PM) and polyguluronate (PG) in more intense conditions. The results indicated that the oxidation process continued until all reducing ends were converted to carboxyl groups. The o-diol could directly oxidize to o-dialdehyde. This study provides a MS based elucidation of the mechanism by which alginate cleaves to oligosaccharides through ozonation.

Advances in oligosaccharides production from brown seaweeds: extraction, characterization, antimetabolic syndrome, and other potential applications

Brown seaweeds are a promising source of bioactive substances, particularly oligosaccharides. This group has recently gained considerable attention due to its diverse cell wall composition, structure, and wide-spectrum bioactivities. This review article provides a comprehensive update on advances in oligosaccharides (OSs) production from brown seaweeds and their potential health applications. It focuses on advances in feedstock pretreatment, extraction, characterization, and purification prior to OS use for potential health applications. Brown seaweed oligosaccharides (BSOSs) are extracted using various methods. Among these, enzymatic hydrolysis is the most preferred, with high specificity, mild reaction conditions, and low energy consumption. However, the enzyme selection and hydrolysis conditions need to be optimized for desirable yield and oligosaccharides composition. Characterization of oligosaccharides is essential to determine their structure and properties related to bioactivities and to predict their most suitable application. This is well covered in this review. Analytical techniques such as high-performance liquid chromatography (HPLC), gas chromatography (GC), and nuclear magnetic resonance (NMR) spectroscopy are commonly applied to analyze oligosaccharides. BSOSs exhibit a range of biological properties, mainly antimicrobial, anti-inflammatory, and prebiotic properties among others. Importantly, BSOSs have been linked to possible health advantages, including metabolic syndrome management. Metabolic syndrome is a cluster of conditions, such as obesity, hypertension, and dyslipidemia, which increase the risk of cardiovascular disease and type 2 diabetes. Furthermore, oligosaccharides have potential applications in the food and pharmaceutical industries. Future research should focus on improving industrial-scale oligosaccharide extraction and purification, as well as researching their potential utility in the treatment of various health disorders.[Figure: see text].

The development of multifunctional sulfated polyguluronic acid-based polymeric micelles for anticancer drug delivery

Numerous disseminated tumor cells specifically overexpress P-selectin. Therefore, it was thought to be a potential target for tumor therapy. Herein, we described a novel P-selectin-targeted glycosyl ligand-sulfated polyguluronic acid (PGS), as an oriented carrier of P-selectin-targeted drug delivery system. Specifically, the PGS-SS-DOX polymeric micelles were constructed to confirm the practicability of the PGS carrier as a new P-selectin-targeted ligand. PGS-SS-DOX micelles comprised P-selectin-targeted PGS, doxorubicin (DOX) as an anticarcinogen, and pH/redox dual-sensitive bio-linker facilitating drug release in tumor tissues. In vitro and in vivo data showed that PGS-SS-DOX micelles significantly increased tumor cell killing capacity and exhibited a favorable biocompatibility comparison with Free-DOX. This work proved that PGS was an ideal low immunogenic, biodegradable drug carrier for the delivery of anti-cancer drugs. The facile PGS-SS-drug micelle system provided enormous opportunities for treating disseminated tumors utilizing many irreplaceable anticarcinogens.

Enzymatic depolymerization of alginate by two novel thermostable alginate lyases from Rhodothermus marinus

Alginate (alginic acid) is a linear polysaccharide, wherein (1→4)-linked β-D-mannuronic acid and its C5 epimer, α-L-guluronic acid, are arranged in varying sequences. Alginate lyases catalyze the depolymerization of alginate, thereby cleaving the (1→4) glycosidic linkages between the monomers by a β-elimination mechanism, to yield unsaturated 4-deoxy-L-erythro-hex-4-enopyranosyluronic acid (Δ) at the non-reducing end of resulting oligosaccharides (α-L-erythro configuration) or, depending on the enzyme, the unsaturated monosaccharide itself. In solution, the released free unsaturated monomer product is further hydrated in a spontaneous (keto-enol tautomerization) process to form two cyclic stereoisomers. In this study, two alginate lyase genes, designated alyRm3 and alyRm4, from the marine thermophilic bacterium Rhodothermus marinus (strain MAT378), were cloned and expressed in Escherichia coli. The recombinant enzymes were characterized, and their substrate specificity and product structures determined. AlyRm3 (PL39) and AlyRm4 (PL17) are among the most thermophilic and thermostable alginate lyases described to date with temperature optimum of activity at ∼75 and 81°C, respectively. The pH optimum of activity of AlyRm3 is ∼5.5 and AlyRm4 at pH 6.5. Detailed NMR analysis of the incubation products demonstrated that AlyRm3 is an endolytic lyase, while AlyRm4 is an exolytic lyase, cleaving monomers from the non-reducing end of oligo/poly-alginates.

The Use of Carbohydrate Biopolymers in Plant Protection against Pathogenic Fungi

Fungal pathogens cause significant yield losses of many important crops worldwide. They are commonly controlled with fungicides which may have negative impact on human health and the environment. A more sustainable plant protection can be based on carbohydrate biopolymers because they are biodegradable and may act as antifungal compounds, effective elicitors or carriers of active ingredients. We reviewed recent applications of three common polysaccharides (chitosan, alginate and cellulose) to crop protection against pathogenic fungi. We distinguished treatments dedicated for seed sowing material, field applications and coating of harvested fruits and vegetables. All reviewed biopolymers were used in the three types of treatments, therefore they proved to be versatile resources for development of plant protection products. Antifungal activity of the obtained polymer formulations and coatings is often enhanced by addition of biocontrol microorganisms, preservatives, plant extracts and essential oils. Carbohydrate polymers can also be used for controlled-release of pesticides. Rapid development of nanotechnology resulted in creating new promising methods of crop protection using nanoparticles, nano-/micro-carriers and electrospun nanofibers. To summarize this review we outline advantages and disadvantages of using carbohydrate biopolymers in plant protection.

Alginate oligosaccharides: The structure-function relationships and the directional preparation for application

Alginate oligosaccharides (AOS) are degradation products of alginate extracted from brown algae. With low molecular weight, high water solubility, and good biological activity, AOS present anti-inflammatory, antimicrobial, antioxidant, and antitumor properties. They also exert growth-promoting effects in animals and plants. Three types of AOS, mannuronate oligosaccharides (MAOS), guluronate oligosaccharides (GAOS), and heterozygous mannuronate and guluronate oligosaccharides (HAOS), can be produced from alginate by enzymatic hydrolysis. Thus far, most studies on the applications and biological activities of AOS have been based mainly on a hybrid form of HAOS. To improve the directional production of AOS for practical applications, systematic studies on the structures and related biological activities of AOS are needed. This review provides a summary of current understanding of structure-function relationships and advances in the production of AOS. The current challenges and opportunities in the application of AOS is suggested to guide the precise application of AOS in practice.

Preparation and potential applications of alginate oligosaccharides

Alginate, a linear polymer consisting of β-D-mannuronic acid (M) and α-L-guluronic acid (G) with 1,4-glycosidic linkages and comprising 40% of the dry weight of algae, possesses various applications in the food and nutraceutical industries. However, the potential applications of alginate are restricted in some fields because of its low water solubility and high solution viscosity. Alginate oligosaccharides (AOS) on the other hand, have low molecular weight which result in better water solubility. Hence, it becomes a more popular target to be researched in recent years for its use in foods and nutraceuticals. AOS can be obtained by multiple degradation methods, including enzymatic degradation, from alginate or alginate-derived poly G and poly M. AOS have unique bioactivity and can bring human health benefits, which render them potentials to be developed/incorporated into functional food. This review comprehensively covers methods of the preparation and analysis of AOS, and discussed the potential applications of AOS in foods and nutraceuticals.

Comparison of Biochemical Characteristics, Action Models, and Enzymatic Mechanisms of a Novel Exolytic and Two Endolytic Lyases with Mannuronate Preference

Recent explorations of tool-like alginate lyases have been focused on their oligosaccharide-yielding properties and corresponding mechanisms, whereas most were reported as endo-type with α-L-guluronate (G) preference. Less is known about the β-D-mannuronate (M) preference, whose commercial production and enzyme application is limited. In this study, we elucidated Aly6 of Flammeovirga sp. strain MY04 as a novel M-preferred exolytic bifunctional lyase and compared it with AlgLs of Pseudomonas aeruginosa (Pae-AlgL) and Azotobacter vinelandii (Avi-AlgL), two typical M-specific endolytic lyases. This study demonstrated that the AlgL and heparinase_II_III modules play indispensable roles in determining the characteristics of the recombinant exo-type enzyme rAly6, which is preferred to degrade M-enriched substrates by continuously cleaving various monosaccharide units from the nonreducing end, thus yielding various size-defined ΔG-terminated oligosaccharides as intermediate products. By contrast, the endolytic enzymes Pae-rAlgL and Avi-rAlgL varied their action modes specifically against M-enriched substrates and finally degraded associated substrate chains into various size-defined oligosaccharides with a succession rule, changing from ΔM to ΔG-terminus when the product size increased. Furthermore, site-directed mutations and further protein structure tests indicated that H¹⁹⁵NHSTW is an active, half-conserved, and essential enzyme motif. This study provided new insights into M-preferring lyases for novel resource discoveries, oligosaccharide preparations, and sequence determinations.

Single-Point Mutation Near Active Center Increases Substrate Affinity of Alginate Lyase AlgL-CD

Alginate lyases have been widely used for the preparation of bioactive alginate oligosaccharides. An alginate lyase AlgL-CD was rationally designed by introducing alkaline amino acid residues near active center to increase activity. One of its mutants E226K presented much higher activity than wild-type AlgL-CD. Substrate affinity of E226K increased 10 folds as the K_m values indicated. The spectra of intrinsic emission fluorescence and circular dichroism of E226K suggested the whole enzyme turned to be more flexible. The 8-anilino-1-naphthalenesulfonate (ANS)-binding assay showed that the hydrophobic active center of E226K was more available to ligand. Molecular dynamic analysis of the enzyme-substrate complex showed that lid loops of the active center in E226K turned to be more opened up, which might contribute to the increase of substrate-binding affinity. Meanwhile, the catalytic residue of E226K was closer to the hydrogen donor C5 atom of the substrate to increase catalysis rate. The final degradation products of alginate by E226K were determined to be identical with that of AlgL-CD. This study provides guidance for improving enzymatic preparation efficiency of bioactive alginate oligosaccharides.

Field demonstration of irradiated sodium alginate as tea production booster

Sodium alginate oligomers were tested for tea plant growth promoter and anti-fungal agent in this experiment. Sodium alginate solutions were irradiated by Co-60 gamma radiation with different radiation doses to produce the oligomers. Irradiated solutions were then diluted into 150, 300 and 500 ppm prior to foliar application. Solutions were applied through foliar spraying at 7 days interval and the best response of tea plants in terms of various attributes were recorded. Tea buds were collected in 10 days of interval and the growth attributes like- total number of buds, fresh weight of buds, average leaf area and weight per bud, weight of made tea etc. were calculated. The experiment was continued up to 12 weeks and the attributes were averaged to get results per plucking. 12 kGy radiation doses along with 300ppm solution showed the best results and about 36% increase in productivity was found based on the fresh weight of buds. Total fungal count in tea leaves was also found to be reduced greatly. Based on the present study, irradiated sodium alginate could be used as safe and environmentally friendly agent to increase tea production.

Preparation of alginate oligosaccharides and their biological activities in plants: A review

Alginate oligosaccharide (AOS) is the degradation product of alginates extracted from brown algae. As a multifunctional oligomer, it has attracted widespread attention in plant research. Different methods of preparation generate AOS possessing diverse structural properties, and result in differences in AOS activity. In this review, the methods of preparation and characterization of AOS are briefly summarized, followed by a systematic introduction to the activity and mechanisms of AOS in plants. AOS can act as a growth promoter at different growth stages of plants. AOS also enhances resistance to pathogens, drought, salt, heavy metals and other stressors by triggering plant immunity, exerting bioactivity just like a pathogen-associated molecular pattern. In addition, AOS can regulate ABA biosynthesis and metabolite to preserve fruit quality and enhance shelf life. This review provides a comprehensive summary of the biological activity of AOS in plants, which will support research and the application of AOS treatments for plants in the future.

Oligomannuronate prevents mitochondrial dysfunction induced by IAPP in RINm5F islet cells by inhibition of JNK activation and cell apoptosis

Background

Oligomannuronates (OM) are natural products from alginate that is frequently used as food supplement. The aim of this study was to investigate the in vitro protective effects of OM on RINm5F cells against human Islet amyloid polypeptide (IAPP) induced mitochondrial dysfunction, as well as the underlying mechanisms.

Methods

In the present study, we obtained several kinds of OM with different molecular masses, and then we used RINm5F cells as a model to elucidate the involvement of JNK signal pathway in hIAPP-induced mitochondrial dysfunction in pancreatic beta cells, and the protective effects of OM are associated with its ability to attenuate the mitochondrial dysfunction.

Results

Our results demonstrated that human IAPP induced mitochondrial dysfunction, as evidence by loss of ΔΨm and ATP content, and decrease in oxygen consumption and complex activities, was accompanied by JNK activation, changes in the expressions of Bcl-2 and Bax proteins, release of cytochrome c (Cyto-c) and apoptosis inducing factor (AIF) from mitochondria into cytosol. Interestingly, the human IAPP induced damage in RINm5F cells were effectively restored by co-treatment of OM. Moreover, JNK activation was required for the OM mediated changes in RINm5F cells.

Conclusions

OM prevented mitochondrial dysfunction induced by human IAPP in RINm5F islet cells through JNK dependent signaling pathways.

Biochemical Characterization of a New Oligoalginate Lyase and Its Biotechnological Application in Laminaria japonica Degradation

Oligoalginate lyases catalyze the degradation of alginate polymers and oligomers into monomers, a prerequisite for biotechnological utilizing alginate. In this study, we report the cloning, expression and biochemical characterization of a new polysaccharide lyase (PL) family 17 oligoalginate lyase, OalV17, from the marine bacterium Vibrio sp. SY01. The recombinant OalV17 showed metal ion independent and detergent resistant properties. Furthermore, OalV17 is an exo-type enzyme that yields alginate monomers as the main product and recognizes alginate disaccharides as the minimal substrate. Site-directed mutagenesis followed by kinetic analysis indicates that the residue Arg²³¹ plays a key role in substrate specificity. Furthermore, a rapid and efficient alginate monomer-producing method was developed directly from Laminaria japonica. These results suggest that OalV17 is a potential candidate for saccharification of alginate.

Combined enzymatic hydrolysis and selective fermentation for green production of alginate oligosaccharides from Laminaria japonica

Alginate oligosaccharides (AOS) showed various biological activities. Traditional protocol for producing AOS was a multiple-step and high-pollution procedure. In this study, a rapid and efficient AOS producing method was developed directly from Laminaria japonica. Natural sun-dried L. japonica with a feed ratio of 1:7 (w/v) was pretreated using cellulase with a dry weight of 3%, for releasing the fermentable sugars (8.5 g/L glucose and 15.2 g/L mannitol). Then, the engineered yeast Yarrowia lipolytica strain with alginate lyase activity was grown using an algae-based medium. After fermentation for 72 h, glucose and mannitol were completely consumed, and 71.8 mM AOS was extracted from the fermentation supernatant. The degree of polymerization (DP) was ranging from 2 to 3. The recovery yield of AOS was about 91.7%. The purity of the extracted AOS was 92.6%. Overall, our work provided new insights for the development of green biotechnologies for oligosaccharide production from seaweed.

Microwave-Assisted Degradation of Polysaccharide from Polygonatum sibiricum and Antioxidant Activity

Four polysaccharide fractions (P-1: 71.40%, P-2: 1.95%, P-3: 1.14%, P-4: 1.64%) were isolated from crude Polygonatum sibiricum polysaccharide (PSP), processed by water extraction, ethanol precipitation, and further separated with diethylaminoethyl cellulose-52 anion-exchange chromatography. Their molecular weights and monosaccharide compositions were characterized by high performance gel chromatography with evaporative light scattering detector and ultraviolet-visible detector. The antioxidant activity of four polysaccharides fractions were assessed by the electron transfer menchanism (DPPH, ferric reducing power, and ABST assays) and chelation of transition metals (Fe²⁺ and Cu²⁺ chelation ability). The highest content fraction P-1 exhibited the lowest antioxidant activity, and the ranking of antioxidant capacity was P-4 > P-3 > P-2 > PSP > P-1. After processed by microwave-assisted degradation, the molecular weight of P-1 was decreased from 2.99 × 10⁵ to 2.33 × 10³ Da, while the antioxidant activity of degraded P-1 was about eightfold higher than natural P-1. These results indicated that the proposed microwave-assisted degradation approach was an efficacious methodology to improve their bioactivity by lower the molecular weight of polysaccharides. PRACTICAL APPLICATION: This study provided an environmentally friendly, convenient and efficient microwave-assisted degradation technology to process the neutral polysaccharides from Polygonatum sibiricum. The results could be used for the development and utilization of various plant polysaccharides as a kind of food supplement in our daily life.

Purification and characterization of alginate lyase from Sphingomonas sp. ZH0

Alginate lyases degrade alginate in a beta-elimination reaction to produce oligosaccharides. Thus, alginate lyases are widely used in the food/pharmaceutical industries and are commercially valuable. In this study, four alginate lyase encoding genes were successfully cloned from Sphingomonas sp. ZH0. The expression systems of these alginate lyases were then constructed in Escherichia coli cells. The recombinant ZH0-I, ZH0-II, ZH0-III and ZH0-IV were purified from E. coli cells and were confirmed to be monomeric enzymes with molecular weights of approximately 91, 52, 67, and 113 kDa, respectively. The conditions for enzymes to have the highest specific lyase activities were 53.2 U/mg, 42 °C, pH 7.0 for ZH0-I, 103.9 U/mg, 47 °C, pH 6.5 for ZH0-II, 13.7 U/mg, 52 °C, pH 7.5 for ZH0-III, and 12.3 U/mg, 37 °C, pH 7.0 for ZH0-IV, respectively. These recombinant enzymes were stable over a pH range. Moreover, the enzymes were active in the absence of salt ions, and their activities were substantially reduced by the addition of HgCl₂. ZH0-I, ZH0-II and ZH0-III belong to endotype alginate lyases, while ZH0-IV is an exotype alginate lyase. All types could degrade both poly-β-d-mannuronate and poly-α-l-guluronate blocks, yielding alginate oligosaccharides as the main product. The K_m and V_max values were 0.51 mg/ml and 56.18 U/ml for ZH0-I, 0.47 mg/ml and 27.5 U/ml for ZH0-II, 0.55 mg/ml and 60.24 U/ml for ZH0-III, and 0.41 mg/ml and 5.53 U/ml for ZH0-IV, respectively. These features indicate that these alginate lyases are promising candidates for producing antioxidants from alginates in industrial applications.

Cloning, Expression, and Biochemical Characterization of Two New Oligoalginate Lyases with Synergistic Degradation Capability

Alginate, the most abundant carbohydrate presents in brown macroalgae, has recently gained increasing attention as an alternative biomass for the production of biofuel. Oligoalginate lyases catalyze the degradation of alginate oligomers into monomers, a prerequisite for bioethanol production. In this study, two new oligoalginate lyase genes, oalC6 and oalC17, were cloned from Cellulophaga sp. SY116, and expressed them in Escherichia coli. The deduced oligoalginate lyases, OalC6 and OalC17, belonged to the polysaccharide lyase (PL) family 6 and 17, respectively. Both showed less than 50% amino acid identity with all of the characterized oligoalginate lyases. Moreover, OalC6 and OalC17 could degrade both alginate polymers and oligomers into monomers in an exolytic mode. Substrate specificity studies demonstrated that OalC6 preferred α-L-guluronate (polyG) blocks, while OalC17 preferred poly β-D-mannuronate (polyM) blocks. The combination of OalC6 and OalC17 showed synergistic degradation ability toward both alginate polymers and oligomers. Finally, an efficient process for the production of alginate monomers was established by combining the new-isolated exotype alginate lyases (i.e., OalC6 and OalC17) and the endotype alginate lyase AlySY08. Overall, our work provides new insights for the development of novel biotechnologies for biofuel production from seaweed.

Cloning and characterization of a new cold-adapted and thermo-tolerant ι-carrageenase from marine bacterium Flavobacterium sp. YS-80-122

ι-Carrageenases play a role in marine ι-carrageenan degradation, and their enzymatic hydrolysates are thought to be excellent antioxidants. In this study, we identified a new ι-carrageenase, encoded by cgiF, in psychrophilic bacterium Flavobacterium sp. YS-80-122. The deduced ι-carrageenase, CgiF, belongs to glycoside hydrolase family 82 and shows less than 40% amino acid identity with characterized ι-carrageenases. The activity of recombinant CgiF peaked at 30°C (1,207.8U/mg). Notably, CgiF is a cold-adapted ι-carrageenase, which showed 36.5% and 57% of the maximum activity at 10°C and 15°C, respectively. In addition, it is a thermo-tolerant enzyme that recovered 58.2% of its initial activity after heat shock. Furthermore, although the activity of CgiF was enhanced by NaCl, the enzyme is active in absence of NaCl. This study also shows that CgiF is an endo-type ι-carrageenase that hydrolyzes β-1,4-linkages of ι-carrageenan, yielding neo-ι-carratetraose as the main product. Its cold-adaptation, thermo-tolerance, NaCl independence and high neo-ι-carratetraose yield make CgiF an excellent candidate for industrial applications in production of ι-carrageen oligosaccharides from seaweed polysaccharides.

Purification and Characterization of a New Alginate Lyase from Marine Bacterium Vibrio sp. SY08

Unsaturated alginate disaccharides (UADs), enzymatically derived from the degradation of alginate polymers, are considered powerful antioxidants. In this study, a new high UAD-producing alginate lyase, AlySY08, has been purified from the marine bacterium Vibrio sp. SY08. AlySY08, with a molecular weight of about 33 kDa and a specific activity of 1070.2 U/mg, showed the highest activity at 40 °C in phosphate buffer at pH 7.6. The enzyme was stable over a broad pH range (6.0–9.0) and retained about 75% activity after incubation at 40 °C for 2 h. Moreover, the enzyme was active in the absence of salt ions and its activity was enhanced by the addition of NaCl and KCl. AlySY08 resulted in an endo-type alginate lyase that degrades both polyM and polyG blocks, yielding UADs as the main product (81.4% of total products). All these features made AlySY08 a promising candidate for industrial applications in the production of antioxidants from alginate polysaccharides.

Cloning and characterization of two thermo- and salt-tolerant oligoalginate lyases from marine bacterium Halomonas sp

Two new alginate lyase genes, oalY1 and oalY2, have been cloned from the newly isolated marine bacterium Halomonas sp. QY114 and expressed in Escherichia coli The deduced alginate lyases, OalY1 and OalY2, belonged to polysaccharide lyase (PL) family 17 and showed less than 45% amino acid identity with all of the characterized oligoalginate lyases. OalY1 and OalY2 exhibited the highest activities at 45°C and 50°C, respectively. Both of them showed more than 50% of the highest activity at 60°C, and 20% at 80°C. In addition, they were salt-dependent and salt-tolerant since both of them showed the highest activity in the presence of 0.5 M NaCl and preserved 63% and 68% of activity in the presence of 3 M NaCl. Significantly, OalY1 and OalY2 could degrade both polyM and polyG blocks into alginate monosaccharides in an exo-lytic type, indicating that they are bifunctional alginate lyases. In conclusion, our study indicated that OalY1 and OalY2 are good candidates for alginate saccharification application, and the salt-tolerance may present an exciting new concept for biofuel production from native brown seaweeds.

Low molecular weight guluronate prevents TNF-α-induced oxidative damage and mitochondrial dysfunction in C2C12 skeletal muscle cells

Muscle wasting is associated with a variety of chronic or inflammatory disorders. Evidence suggests that inflammatory cytokines play a vital role in muscle inflammatory pathology and this may result in oxidative damage and mitochondrial dysfunction in skeletal muscle. In our study, we used microwave degradation to prepare a water-soluble low molecular weight guluronate (LMG) of 3000 Da from Fucus vesiculosus obtained from Canada, the Atlantic Ocean. We demonstrated the structural characteristics, using HPLC, FTIR and NMR of LMG and investigated its effects on oxidative damage and mitochondrial dysfunction in C2C12 skeletal muscle cells induced by tumor necrosis factor alpha (TNF-α), a cell inflammatory cytokine. The results indicated that LMG could alleviate mitochondrial reactive oxygen species (ROS) production, increase the activities of antioxidant enzymes (GSH and SOD), promote mitochondrial membrane potential (MMP) and upregulate the expression of mitochondrial respiratory chain protein in TNF-α-induced C2C12 cells. LMG supplement also increased the mitochondrial DNA copy number and mitochondrial biogenesis related genes in TNF-α-induced C2C12 cells. LMG may exert these protective effects through the nuclear factor kappa B (NF-κB) signaling pathway. These suggest that LMG is capable of protecting TNF-α-induced C2C12 cells against oxidative damage and mitochondrial dysfunction.

Cloning and characterization of the first polysaccharide lyase family 6 oligoalginate lyase from marine Shewanella sp. Kz7

Alginate, the most abundant carbohydrate in brown macroalgae, is widely used in the food and pharmaceutical industries. Recently, alginate has attracted increasing attention, as it may serve as an alternative biomass for the production of biofuel. The degradation of alginate into monomeric units is the prerequisite for bioethanol production. All known oligoalginate lyases belong to the polysaccharide lyase (PL) family 7, 14, 15 and 17, and most of them preferred to degrade the polyM blocks to yield 4-deoxy-l-erythro-5-hexoseulose uronic acid as the primary product. In this study, we cloned an oligoalginate lyase gene, oalS6, from Shewanella sp. Kz7 and expressed it in Escherichia coli. The PL family 6 oligoalginate lyase (OalS6) has no significant sequence similarity with other known oligoalginate lyases. OalS6 contains a chondroitinase-like domain and was assigned to the PL family 6. This lyase is an exo-type oligoalginate lyase and prefer to depolymerize polyG block into 2, 4, 5, 6-tetrahydroxytetrahydro-2H-pyran-2-carboxylic acid. All of these results indicate that OalS6 is a novel oligoalginate lyase that is structurally and functionally different from other known oligoalginate lyases. This finding provides new insights into the development of biofuel processing biotechnologies from seaweed.

Regioselective silyl/acetate exchange of disaccharides yields advanced glycosyl donor and acceptor precursors

Glycoconjugates are composed of carbohydrate building blocks linked together in a multitude of ways giving rise to diverse biological functions. Carbohydrates are especially difficult to synthetically manipulate because of the similar reactivity of their numerous and largely equivalent hydroxyl groups. Hence, methodologies for both the efficient protection and selective modification of carbohydrate alcohols are considered important synthetic tools in organic chemistry. When per-O-TMS protected mono- or disaccharides in a mixture of pyridine and acetic anhydride are treated with acetic acid, regioselective exchange of silicon for acetate protecting groups occurs. Acid concentration, thermal conditions, and microwave assistance mediate the silyl/acetate exchange reaction. Regiocontrol is achieved by limiting the equivalents of acetic acid, and microwave irradiation hastens the process. We coined the term Regioselective Silyl Exchange Technology (ReSET) to describe this process, which essentially sets the protecting groups anew. To demonstrate the scope of the reaction, the conditions were applied to lactose, melibiose, cellobiose, and trehalose. ReSET provided rapid access to a wide range of orthogonally protected disaccharides that would otherwise require multiple synthetic steps to acquire. The resulting bifunctional molecules are poised to serve as modular building blocks for more complex glycoconjugates.