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Brown algae, as the main source of alginate, are a type of marine biomass with a very high output. Alginate, a polysaccharide composed of β-D-mannuronic acid (M) and α-L-guluronic acid (G), has great potential for applications in the food, cosmetic and pharmaceutical industries. Alginate lyases (Alys) can degrade alginate polymers into oligosaccharides or monosaccharides, resulting in a broad application field. Alys can be used for both the production of alginate oligosaccharides and the biorefinery of brown algae. In view of their important functions, an increasing number of Alys have been isolated and characterized. For better application, a comprehensive understanding of Alys is essential. Therefore, in this paper, we summarized recently discovered Alys, discussed their characteristics, and introduced their structural properties, degradation patterns and biological roles in alginate-degrading organisms. In addition, applications of Alys have been illustrated with examples. This paper provides a relatively comprehensive description of Alys, which is significant for Alys exploration and application., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Marine-polysaccharide degrading enzymes have recently been studied extensively. They are particularly interesting as they catalyze the cleavage of glycosidic bonds in polysaccharide macromolecules and produce oligosaccharides with low degrees of polymerization. Numerous findings have demonstrated that marine polysaccharides and their biotransformed products possess beneficial properties including antitumor, antiviral, anticoagulant, and anti-inflammatory activities, and they have great value in healthcare, cosmetics, the food industry, and agriculture. Exploitation of enzymes that can degrade marine polysaccharides is in the ascendant, and is important for high-value use of marine biomass resources. In this review, we describe research and prospects regarding the classification, biochemical properties, and catalytic mechanisms of the main types of marine-polysaccharide degrading enzymes, focusing on chitinase, chitosanase, alginate lyase, agarase, and carrageenase, and their product oligosaccharides. The state-of-the-art discussion of marine-polysaccharide degrading enzymes and their properties offers information that might enable more efficient production of marine oligosaccharides. We also highlight current problems in the field of marine-polysaccharide degrading enzymes and trends in their development. Understanding the properties, catalytic mechanisms, and modification of known enzymes will aid the identification of novel enzymes to degrade marine polysaccharides and facilitation of their use in various biotechnological processes., (© 2020 Institute of Food Technologists®.)

Ionizing radiation is increasingly used to successfully diagnose many human health problems, but ionizing radiation may cause damage to organs/tissues in the living organisms such as the spleen, liver, skin, and brain. Many radiation protective agents have been discovered, with the deepening of radiation research. Unfortunately, these protective agents have many side effects, which cause drug resistance, nausea, vomiting, osteoporosis, etc. The polysaccharides extracted from natural sources are widely available and low in toxicity. In vivo and in vitro experiments have demonstrated that polysaccharides have anti-radiation activity through anti-oxidation, immune regulation, protection of hematopoietic system and protection against DNA damage. Recently, some studies have shown that polysaccharides were resistant to radiation. In the review, the anti-radiation activities of polysaccharides from different sources are summarized, and the anti-radiation mechanisms are discussed as well. It can be used to develop more effective anti-radiation management drugs., (Copyright © 2020. Published by Elsevier B.V.)

Agar is a polysaccharide mixture extracted from red algae. Agar has been widely used in food, medicine and biochemistry, because of its gelling properties and stability. However, sulfate groups in the structure of agar weaken the gel strength of agar; hence, sulfate removal is necessary to improve the agar quality. The commonly used alkali desulfation greatly pollutes the environment, and enzymatic desulfation is costly due to the need for a large amount of the enzyme. In this work, microorganisms were for the first time used for agar desulfation, taking advantage of the sulfur demand of microorganisms themselves. This allows the removal of agar sulfate groups to be eco-friendly and effective. Firstly, microorganism strains were screened with agar as the sole sulfur source. Then 4 microorganism-based agar desulfation techniques, sulfate removal from agar liquid at 60 °C, from an solid agar plate at 37 °C, from freshly-prepared agar slices in liquid medium, and from agar strips without pretreatment (ASWP) in liquid medium, were established and compared. Finally, by using Priestia megaterium WMX, the sulfate removal rate from ASWP reached 74.67%, and the gel strength increased by 187%, reaching 1173 g cm−2. Therefore, the agar quality was greatly improved by sulfate removal with microorganisms. The microorganism-based agar desulfation technique established in this work is easy-to-perform, cost effective, and an eco-friendly way to improve agar quality and has the potential to be applied on the industrial scale. [ABSTRACT FROM AUTHOR]

Polymerized guluronates (polyG)-specific alginate lyase with lower polymerized mannuronates (polyM)-degrading activity, superior stability, and clear action mode is a powerful biotechnology tool for the preparation of AOSs rich in M blocks. In this study, we expressed and characterized a polyG-specific alginate lyase OUC-FaAly7 from Formosa agariphila KMM3901. OUC-FaAly7 belonging to polysaccharide lyase (PL) family 7 had highest activity (2743.7 ± 20.3 U/μmol) at 45 °C and pH 6.0. Surprisingly, its specific activity against polyG reached 8560.2 ± 76.7 U/μmol, whereas its polyM-degrading activity was nearly 0 within 10 min reaction. Suggesting that OUC-FaAly7 was a strict polyG-specific alginate lyase. Importantly, OUC-FaAly7 showed a wide range of temperature adaptations and remarkable temperature and pH stability. Its relative activity between 20 °C and 45 °C reached >90 % of the maximum activity. The minimum identifiable substrate of OUC-FaAly7 was guluronate tetrasaccharide (G4). Action process and mode showed that it was a novel alginate lyase digesting guluronate hexaose (G6), guluronate heptaose (G7), and polymerized guluronates, with the preferential generation of unsaturated guluronate pentasaccharide (UG5), although which could be further degraded into unsaturated guluronate disaccharide (UG3) and trisaccharide (UG2). This study contributes to illustrating the catalytic properties, substrate recognition, and action mode of novel polyG-specific alginate lyases. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, carboxymethylation and TEMPO-mediated oxidation were compared for their ability to introduce carboxyl groups to polysaccharides, using cellulose and chitin as model polysaccharides. The carboxyl group contents and changes in the molecular weight of carboxymethylated and TEMPO-oxidized cellulose/chitin were measured. The results revealed that carboxymethylation achieved higher carboxyl group contents, with values of 4.99 mmol/g for cellulose and 4.46 mmol/g for chitin, whereas for TEMPO-oxidized cellulose and chitin, the values were 1.64 mmol/g and 1.12 mmol/g, respectively. As a consequence of TEMPO-mediated oxidation, polysaccharides underwent degradation, leading to a decrease in the molecular weight of 42.46 % for oxidized cellulose and 64.5 % for oxidized chitin. Additionally, the crystallinity of carboxymethylated polysaccharides decreased with an increase in the carboxyl group contents, whereas that of TEMPO-oxidized polysaccharides remained unchanged. Furthermore, TEMPO-mediated oxidation selectively oxidized C6 primary hydroxyls, while carboxylmethylation converted all the hydroxyl groups on the polysaccharides. [ABSTRACT FROM AUTHOR]

Dialdehyde-based cross-linking agents are widely used in the cross-linking of amino group-containing macromolecules. However, the most commonly used cross-linking agents, glutaraldehyde (GA) and genipin (GP), have safety issues. In this study, a series of dialdehyde derivatives of polysaccharides (DADPs) were prepared by oxidation of polysaccharides, and their biocompatibility and cross-linking properties were tested using chitosan as a model macromolecule. The DADPs showed outstanding cross-linking and gelation properties comparable to GA and GP. The DADPs and hydrogels cross-linked with the DADPs exhibited excellent cytocompatibility and hemocompatibility with different concentrations while significant cytotoxicity was observed in GA and GP. The experimental results showed that the cross-linking effect of DADPs increased along with their oxidation degree. The outstanding cross-linking effect of the DADPs show a potential for use in the cross-linking of biomacromolecules with amino groups and could be an adequate alternative to existing cross-linkers. [ABSTRACT FROM AUTHOR]