Decomposition Of Alginate Research Articles

Influence of temperature during pyrolysis of Fe-alginate: Unraveling the pathway towards highly active Fe/C catalysts

Transition metals supported on carbons play an important role in catalysis and energy storage. By pyrolysis of metal alginate, highly active catalysts for the Fischer-Tropsch synthesis (FTS) can be produced. However, the evolution of the carbon (alginate) and transition metal (Fe3+) during pyrolysis remains largely unknown and was herein corroborated with several advanced in situ techniques. Initially, Fe3+ was reduced to Fe2+, while bound to alginate. FeO nucleated above 300 °C, destabilizing the alginate functional groups. Increasing temperatures improved carbonization of the carbon support, which facilitated reduction of FeO to α-Fe at 630 °C. Catalysts were produced by pyrolysis between 400 and 700 °C, where the highest FTS activity (612 µmolCO gFe−1 s−1) was achieved for the sample pyrolyzed at low temperature. Lower metal loading, due to less decomposition of alginate, moderated sintering and yielded larger catalytic surface areas. The results provide valuable knowledge for rational design of metal-alginate-based materials.

Insights into the mechanism of cyanobacteria removal by the algicidal fungi Bjerkandera adusta and Trametes versicolor.

Fungal mycelia can eliminate almost all cocultured cyanobacterial cells within a short time. However, molecular mechanisms of algicidal fungi are poorly understood. In this study, a time‐course transcriptomic analysis of algicidal fungus Bjerkandera adusta T1 was applied to investigate gene expression and regulation. A total of 132, 300, 422, and 823 differentially expressed genes (DEGs) were identified at 6, 12, 24, and 48 hr, respectively. Most DEGs exhibited high endopeptidase activity, cellulose catabolic process, and transmembrane transporter activity by using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Many decomposition genes encoding endopeptidases were induced a little later in B. adusta T1 when compared with previously investigated algicidal fungus Trametes versicolor F21a. Besides, the accumulated expression of Polysaccharide lyases8 (PL8) gene with peptidoglycan and alginate decomposition abilities was greatly delayed in B. adusta T1 relative to T. versicolor F21a. It was implied that endopeptidases and enzymes of PL8 might be responsible for the strong algicidal ability of B. adusta T1 as well as T. versicolor F21a.

A magnetic macro-porous biochar sphere as vehicle for the activation and removal of heavy metals from contaminated agricultural soil

Remediation of contaminated agricultural soils focused on fixing heavy metals in soils to reduce their bioavailability. However, with the influence of pH, redox potential, and microorganism in the soils, heavy metals were likely to be released from a fixed state. The study aims to investigate magnetic porous biochar spheres and their roles in in situ sorption and removal of heavy metal from the contaminated agricultural soil. The magnetic biochar spheres were prepared using alginate and FeCl3 through a one-step gelation to obtain alginate-Fe3+ gel and subsequently pyrolyzed. Results of Ultraviolet–visible spectrophotometer, X-ray diffraction and Fourier transform infrared spectrometer showed the decomposition of alginate and the formation of Fe3O4 and FeCl2 hydrates nanoparticles on the spheres when the spheres were pyrolyzed at 300 °C. Scanning electron microscope image showed that the CFe300 sphere has a macro-porous structure. The CFe300 sphere exhibited good adsorption capacity of hexavalent chromium from aqueous solution. The CFe300 sphere decreased the bioavailable and total cadmium (II) concentrations from 1.55 ± 0.08 to 0.32 ± 0.04 mg/kg and from 2.81 ± 0.02 to 1.39 ± 0.06 mg/kg, respectively. Moreover, the CFe300 sphere decreased bioavailable and total arsenate (V) concentrations from 1.26 ± 0.003 to 0.85 ± 0.01 mg/kg and from 60.23 ± 0.39 to 27.34 ± 0.94 mg/kg, respectively. Subsequently, addition of water into the soil induced the spheres to leave the soil and float on the surface of soil/water mixture. Thus, the magnetic biochar spheres can be much easier to separate from the soil using magnets.

Photocatalytic alginate fuel cells for energy production and refining of macroalgae

An alginate fuel cell comprising a TiO2-modified carbon sheet (TiO2/C) anode was developed. The power output of the fuel cell and decomposition of alginate were enhanced by solar irradiation of the anode.

A study on torrefaction of Laminaria japonica

Torrefaction of a macroalga Laminaria japonica, a representative macroalga, was carried out in a fixed-bed tubular reactor under nitrogen atmosphere at 423 to 573K. Three useful findings were obtained for torrefaction of L. japonica from this study. Firstly, the major reaction of the microalga may be decomposition of alginate, while the major reaction for torreterrestrial biomass is known to be decomposition of hemicellulose. Even so, H/C vs. O/C (so-called the van Krevelen plot) showed a similar trend between the macroalga and terrestrial biomass. Secondly, an extremely low temperature is effective to obtain a satisfactory energy yield of torrefied macroalga. Thirdly, the ash, nitrogen and sulfur can be considerably eliminated from the macroalga by torrefaction.

Catalytic hydrothermal conversion of macroalgae-derived alginate: effect of pH on production of furfural and valuable organic acids under subcritical water conditions

The hydrothermal decomposition of sodium alginate was analyzed in subcritical water as a function of pH in order to investigate the effects of catalysts on the production of value-added chemicals. A base-catalysed reaction at pH 13 promoted the decomposition of alginate, resulting in the production of lactic acid, fumaric acid and malic acid as major species. At pH 1, monomers (mannuronic acid and guluronic acid), furfural and glycolic acid were predominantly produced by the acid-catalysed hydrothermal decomposition of alginate. Increasing the reaction temperature enhanced both the acid- and base-catalysed reactions, albeit by varying degrees dependent upon the catalyst type. Our results demonstrate that optimizing the reaction temperature and pH is critical for the efficient conversion of seaweed-derived biomass into valuable products.

Invertase stability in alginate beads: Effect of trehalose and chitosan inclusion and of drying methods

The purpose of present work was to analyze the effect of trehalose and chitosan on invertase activity preservation in wet and dried alginate beads, by taking advantage of the well known trehalose protective effect of labile compounds during drying and chitosan improvement on mechanical properties of alginate beads. The beads were subjected to different drying methods (freeze-drying, vacuum and forced air circulation drying) and to a mild thermal treatment (50°C). The size and morphology of the beads were analyzed by optical microscopy and by scanning electron microscopy. The size of the beads was affected by drying at an extent which depended more on the drying method than on the beads composition. Freeze-drying allowed better maintenance of the diameter and circularity of the beads, which showed smoother surface and smaller pores than those generated by vacuum or air drying. The inclusion of chitosan in the gelation media improved enzymatic activity recovery after beads generation; this fact was attributed to a higher mechanical resistance provided by the interaction between alginate and chitosan. There was no effect of trehalose inclusion during this step. Interactions between alginate and chitosan, as well as the effect of trehalose presence were manifested in the FT-IR spectra, and on the increase of alginate decomposition temperatures as detected by DSC. In the alginate beads the enzymatic activity was not enough protected from the damage caused by drying or by heat treatment. The thermal stability of invertase in the dried beads was independent on the type of drying employed, being mainly affected by beads composition. Although trehalose was not effective to prevent enzyme functionality damage during beads generation, it was essential for achieving adequate invertase protection during freezing, drying (freeze-, vacuum or air drying) and thermal treatment.

Alginate-mediated routes to the selective synthesis of complex metal oxide nanostructures

The exceptional electronic, magnetic, optical and catalytic properties demonstrated by many ceramic materials when confined to the nanoscale are well established. However, the synthesis of multicomponent metal oxide nanowires and nanoparticles is notoriously problematic due to the difficulty of controlling homogeneity and achieving the correct stoichiometry. In this paper, we demonstrate a selective route to nanowires or nanoparticles of a quaternary metal oxide product using sodium or ammonium alginate respectively. By pre-organizing metal cations within an alginate gel the nucleation and growth of precursor crystalline phases can be constrained to the nanoscale. On further calcination the alginate decomposition products prevent sintering of these precursor nanoparticles prior to conversion to the final product. The cooperative effect of polymer microstructure and decomposition products allows an exceptional level of control over nucleation, growth and transport of the intermediate phases and subsequently on the particle size and morphology of the final product.

Isolation and characterization of alginate-degrading bacteria for disposal of seaweed wastes

Isolation of novel alginate degrading bacteria for the disposal of seaweed waste in composting process. Decomposition of alginate polymers was checked by the 3,5-dinitrosalicylic acid (DNS) method for reducing sugar, and absorbance at 235 nm for unsaturated sugar. A bacterium A7 was isolated from wakame compost and confirmed to belong to the genus Gracilibacillus by partial 16S rDNA analysis. The optimum condition for the growth of A7 in a medium containing 5 g l(-1) of sodium alginate is as follows: pH, 8.5-9.5; NaCl, 0.5 mol l(-1); temperature, 30 degrees C and polypeptone as nutrient content, 2-5 g l(-1). In a laboratory-scale composting experiment, the alginate content in wakame compost decreased to 14.3% after 72 h of composting from an initial value of 36%, indicating the effectiveness of alginate decomposition of A7 in wakame composting. The bacterium A7 was found to be alginate lyase-producing in genus Gracilibacillus and effective in degrading alginate to oligosaccharides in wakame during composting process. Development of new methods for the disposal of marine wastes and production of functional products.

Disposal of seaweed wakame (Undaria pinnatifida) in composting process by marine bacterium Halomonas sp. AW4

A novel marine bacterium, identified as Halomonas sp. AW4 by partial 16S rDNA analysis, was isolated from the seaweeds in Awaji Island, Japan. Strain AW4 grew well even in the wide NaCl concentration ranges of 0-3 mol/L, where it showed an optimal growth in the presence of 0.5 mol/L NaCl. The organic components were reduced to 73.6% of initial dry weight after 168 h of composting by inoculation of AW4. The microbial community structure became complex after 72 h of composting. The initial content of alginate was 35.6%, which decreased to 15.6% after 168 h of composting. The decomposition of alginate mainly occurred at the late stage of composting, suggesting that the microbial community consisting of various types of microorganisms is effective in degrading alginate. The germination of plant Brassica campestris L. indicated the promotion effect of composted wakame.

Degradation of the seaweed wakame (Undaria pinnatifida) by a composting process with the inoculation of Bacillus sp. HR6.

Disposal of the seaweed wakame (Undaria pinnatifida) by inoculating the halotolerant bacterium Bacillus sp. HR6 was examined in an experimental scale composting system. Strain HR6 was effective in initiating the composting process of wakame, and there was a rapid increase in temperature to over 54.9-55.7 degrees C after 18-20 h. The composting process of wakame could be carried out despite a high NaCl content, 28.2 mg/g, although lower salinity resulted in a shorter lag time and higher weight reduction. In a larger scale composting process with aeration, two peaks of temperature change were found which corresponded well to oxygen consumption and CO2 emission during the process. The pH increased to 8.83 and organic materials were reduced to 93.4% after 72 h. The initial N and C contents were 3.9 and 34.0%, respectively, both of which decreased during the composting process. The changes in the viable cell numbers suggested that strain HR6 predominated before 24 h and other microorganisms including HR6 were present in a mixed state during the later period of composting. The total content of alginate (TA), 32.2% in the initial stage, decreased to 29.2% after 72 h, while water soluble alginate (WSA) increased, indicating that the solubilization and decomposition of alginate had occurred during the composting process.

Determination of D-mannuronic to L-guluronic acids ratio in acid hydrolysis of alginate under improved conditions.

Decomposition of alginate under the hydrolysis procedure with sulfuric acid was evaluated by determining the recovery of monouronates produced and its depolymerization extent. The first three hour hydrolysis with 80% sulfuric acid at 30°C, followed by the two hour hydrolysis with 2 N sulfuric acid at 100°C, resulted in complete hydrolysis with the highest recovery in the conditions examined. Under these conditions, the recovery of authentic uronates was 80.9% for D-man-nuronic acid and 62.8% for L-guluronic acid. Prolonged treatment resulted in a lower recovery of monouronates, and showed indications of an increase in the degradation of monouronates. The degradation products showing reducing power, were detectable with the phenol-sulfuric acid method but undetectable with the carbazole-sulfuric acid method. D-Mannuronic acid to L-guluronic acid ratios (M/G ratio) of nine species of alginates determined by the improved procedure were compared to those determined by the method of Haug and Larsen. The values of M/G ratio obtained by both methods were nearly equal in six species and were slightly different among three species. The modified method, however, showed a 9∼17% higher recovery of monouronates than the method of Haug and Larsen. In addition, the time for the completion of the analysis process was shortened by at least 1/5.

Ecological studies on the littoral attaching micro-algae - X. Decomposition of agar, protein, and organic phosphate by marine epiphytic diatoms.

Decomposition of agar, starch, alginate, casein and organic phosphate (phenolphthalein diphosphate) by eleven clones of marine epiphytic diatoms (Grammatophora marina, Licmophora abbreviata, Navicula spp. and Nitzschia spp.) was examined. Seven clones belonging to genera Navicula and Nitzschia exhibited agar hydrolyzing activity. Five clones (G. marina, Navicula spp. and Nitzschia spp.) hydrolyzed casein. Two clones of Nitzschia decomposed organic phosphate. There was no clone showing starch and alginate decom-position. The results obtained suggest that marine epiphytic diatoms can decompose various organic compounds and may use the products for their growth in natural habitat.