Degradation Of Sodium Alginate Research Articles

Characterization of bifunctional alginate lyase Aly644 and antimicrobial activity of enzymatic hydrolysates.

An alginate lyase gene aly644 encoding a member of polysaccharide lyase family 6 was obtained from a metagenome of Antarctic macroalgae-associated microbes. The gene was expressed heterologously in Escherichia coli, and the recombinant protein was purified using a Ni-NTA His Tag Kit. With sodium alginate as the substrate, recombinant Aly644 exhibited an optimum reaction temperature of 50°C and an optimum reaction pH of 7.0. The Vmax and Km values of Aly644 toward sodium alginate were 112.36 mg/mL·min and 16.75 mg/mL, respectively. Substrate specificity analysis showed that Aly644 was a bifunctional alginate lyase that hydrolyzed both polyguluronic acid and polymannuronic acid. The hydrolysis products of Aly644 with sodium alginate as the substrate were detected by thin-layer chromatography, and were mainly di- and trisaccharides. The oligosaccharides produced by degradation of sodium alginate by Aly644 inhibited the mycelial growth of the plant pathogens Phytophthora capsici and Fulvia fulva; the 50% maximal effective concentration (EC50) values were 297.45 and 452.89 mg/L, and the 90% maximal effective concentration (EC90) values were 1341.45 and 2693.83 mg/L, respectively. This highlights that Aly644 is a potential candidate enzyme for the industrial production of alginate oligosaccharides with low degree of polymerization. Enzyme-hydrolyzed alginate oligosaccharides could support the development of green agriculture as natural antimicrobial agents. KEY POINTS: • An alginate lyase was obtained from a metagenome of Antarctic macroalgae-associated microbes. • Aly644 is a bifunctional alginate lyase with excellent thermostability and pH stability. • The enzymatic hydrolysates of Aly644 directly inhibited Phytophthora capsici and Fulvia fulva.

New insights into the cleaning mechanisms of conductive membrane by NaClO and electric field in terms of protein and polysaccharide degradation

Membrane fouling can be effectively alleviated by using conductive membrane and external electric field in membrane bioreactor. However, the transformation and removal mechanism of foulants during the electrochemical process needs to be further explored. The present work investigated the degradation mechanisms and cleaning efficiency of organic foulants by electric field and sodium hypochlorite (NaClO) on the composite conductive microfiltration membranes. The results show that the electrochemical oxidation obtained a great degradation efficiency of bovine serum albumin (BSA) at current densities of 40 and 80 A/m2, which was equivalent to that of high-dose NaClO (160 mg/L). However, the degradation efficiency of sodium alginate (SA) was much lower than that of BSA under the same cleaning strategy, due to its strong antioxidant activity. It was also found that NaClO oxidation can decompose BSA macromolecules into small molecules instead of mineralization, while electrochemical oxidation can convert dissolved BSA into foams and flocs by electrocoagulation, thus reducing the BSA concentration in the solution. During the electrochemical cleaning, indirect electrochemical oxidation through the formation of strong oxidants played an important role in the degradation of BSA and SA, and the role of OH· was more significant than that of O2·-. The combination of electric fields and NaClO showed great membrane cleaning efficiency. Moreover, the combination of electrochemical cleaning could not only prevent a large number of precursors from being converted to halogenated by-products, but also shorten the chlorination time and reduce the chlorine concentration, which can alleviate the secondary pollution of cleaning solution.

Preparation of low-molecular-weight sodium alginate by ozonation

Low-molecular-weight sodium alginate (LMWSA) has been reported to possess unique physicochemical properties and bioactivities. There is little information available about degradation of sodium alginate by ozonation. Effect of ozonation on molecular weight, molecular weight distribution, color change, M/G ratio, and chemical structure of sodium alginate was investigated. The molecular weight of sodium alginate decreased from 972.3 to 76.7 kDa in the 80-min period of ozonation at 25 °C. Two different degradation-rate constants were calculated. Molecular weight distribution of the LMWSA changed appreciably. Ozonation cannot lead to color change of LMWSA. The M/G ratio of LMWSA was not altered significantly, compared with that of the original alginate. The FT-IR and 13C NMR spectra indicated the chemical structure of LMWSA obtained by ozonation was not altered appreciably. New insight into the ozonation of alginate will be promisingly opened up. Ozonation of sodium alginate can be a alternative for production of LMWSA.

Preparation of alginate oligosaccharide and its effects on decay control and quality maintenance of harvested kiwifruit

Alginate oligosaccharide (AOS) is a biological carbohydrate formed from the degradation of sodium alginate. AOS used in this study was enzymatically prepared and had varying degrees of polymerization (2–8). AOS applied to harvested kiwifruit stored at 25 °C inhibited gray mold, blue mold, and black rot. AOS inhibited pectin solubilization, gene expression of pectin methylesterase and polygalacturonase, and the corresponding enzyme activity of their encoded proteins in kiwifruit. In contrast, AOS induced antioxidant gene expression and enzyme activity, including catalase and superoxide dismutase. The level of total phenols and flavonoids in kiwifruit was also elevated. AOS treatment also had a beneficial effect on fruit quality. Collectively, the results indicate that postharvest treatment with AOS inhibits postharvest decay and prolongs fruit quality by suppressing cell wall degradation and eliciting antioxidants in harvested kiwifruit. AOS has the potential to be used to preserve and extend the postharvest quality of kiwifruit.

Powder Characterization of Calcium Phosphate/Collagen for Bone Implant Application

Calcium phosphate (CaP) is a type of bioceramic material that is biocompatible and bioactive. It is usually used for bone implant application but it lacks mechanical strength. Therefore, sodium alginate (SA), a natural polymer, is combined with CaP to improve its properties of the CaP via precipitation method. The powder formed is then characterized by using FESEM, EDX, FTIR and DTA. Based on the FESEM result, it was confirmed that the SA particles were well embedded and homogeneously dispersed throughout the CaP matrix whereas the EDX result showed that the CaP and SA are pure and were not contaminated with other materials or substances.The FTIR result showed that the intensity of some peaks (3100-3600 cm-1 and 1585-1625cm-1) increased due to the addition of SA but for some peaks the addition of SA leads to a decrease in intensity (1650-1300cm-1 and 1190-976cm-1).This proves that the addition of SA in CaP influenced the intensity peaks and it was confirmed that chemical bonds were formed between these two substances. Meanwhile, the DTA result showed that CaP dehydroxylation occurred in the range of 650-13000C and the thermal degradation of SA happened at 245.80C but the SA thermal degradation temperature improved when it was added to the CaP matrix.

Silk fibroin and sodium alginate blend: Miscibility and physical characteristics

Films of silk fibroin (SF) and sodium alginate (SA) blends were prepared by solution casting technique. The miscibility of SF and SA in those blends was evaluated and scanning electron microscopy (SEM) revealed that SF/SA 25/75wt.% blends underwent microscopic phase separation, resulting in globular structures composed mainly of SF. X-ray diffraction indicated the amorphous nature of these blends, even after a treatment with ethanol that turned them insoluble in water. Thermal analyses of blends showed the peaks of degradation of pristine SF and SA shifted to intermediate temperatures. Water vapor permeability, swelling capacity and tensile strength of SF films could be enhanced by blending with SA. Cell viability remained between 90 and 100%, as indicated by in vitro cytotoxicity test. The SF/SA blend with self-assembled SF globules can be used to modulate structural and mechanical properties of the final material and may be used in designing high performance wound dressing.

Degradation of sodium alginate by γ-irradiation and by oxidative-reductive depolymerization

Methods are described for preparing degraded sodium alginate by oxidative-reductive depolymerization (ORD) and by γ-irradiation. The rate of degradat

Rate of ultrasonic degradation of sodium alginate in solutions of various ionic strengths

Rate of ultrasonic degradation of sodium alginate in solutions of various ionic strengths

Influence of cavitation phenomena on the ultrasonic degradation of sodium alginate in solutions of different ionic strength

Influence of cavitation phenomena on the ultrasonic degradation of sodium alginate in solutions of different ionic strength