An efficiently sustainable dextran-based flocculant: Synthesis, characterization and flocculation

Mechanism analysis of a novel natural cationic modified dextran flocculant and its application in the treatment of blue algal blooms

Blue algae, a type of harmful microalgae, are responsible for causing harmful algal blooms that result in severe environmental issues. To address this problem, a biopolysaccharide-based flocculant was developed for treating blue algae blooms. This flocculant was created by modifying high molecular weight dextran using the natural cationic monomer betaine (Dex-Bet), making it environmentally friendly. Various techniques were used to characterize the prepared Dex-Bet flocculant, including infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA). The effectiveness of the Dex-Bet flocculant was evaluated using kaolin-simulated wastewater. The results showed that the treated supernatant had a transmittance of up to 98.25 %. Zeta potential analysis revealed that the main mechanisms of flocculation were charge neutralization, charge patching, and adsorption bridging. The application of Dex-Bet in treating blue-green algae resulted in a maximum removal rate of 98.2 %. This study provides a potential flocculant for blue algae bloom treatment.

A Functionalized Polysaccharide from Sphingomonas sp. HL-1 for High-Performance Flocculation

The characterization and flocculation mechanism of a biopolymer flocculant produced by Sphingomonas sp. HL-1, were investigated. The bio-flocculant HL1 was identified as an acidic polysaccharide, mainly composed of glucose, and also contained a small amount of mannose, galacturonic acid and guluronic acid. The flocculating activity of the purified HL1 polysaccharide could be activated by trivalent cations, and its flocculation mechanism was mainly charge neutralization and bridging. The working concentration of fermentation broth HL1 in a kaolin suspension was only 1/10,000 (v/v), in which the polysaccharide concentration was about 2 mg/L. The bio-flocculant HL1 maintained high efficiency at a wide range of pH (pH 3-10). It also exhibited good flocculating activity at a temperature range of 20-40 °C; it could even tolerate high salinity and kept activity at a mineralization degree of 50,000 mg/L. Therefore, the bio-flocculant HL1 has a good application prospect in the treatment of wastewater over a broad pH range and in high salinity.

Recent advances in polymer composite, extraction, and their application for wastewater treatment: A review

Wastewater from diverse industrial sectors, agricultural practices and other household activities causes water pollution that result in different environmental issues. The main goals of wastewater treatment are typically to enhance the purity of wastewater and to enable the disposal of domestic and industrial effluents without endangering human health or causing excessive environmental issues. There were several natural and synthetic materials which have been utilized for wastewater treatment, amongst them polymers gain more importance due to their non-toxicity, economic feasibility, abundant availability of sources, renewability, biocompatibility, biodegradability, etc. The organic polymers such as cellulose, chitin, gelatin, alginates, lignin, dextran and other starch derivatives are the most commonly used natural polymers in wastewater treatments. The unique physical and chemical characteristics of the natural polymers make them become an alternative in wastewater treatments such as membrane filtration, adsorption, coagulation, flocculation and ion-exchange process to remove harmful contaminants such as toxic metals, dyes, medicines, pesticides, and so on. The review article discusses natural polymers and related uses in wastewater treatment. This review mainly focused on the wastewater treatment using natural polymers and the techniques involved for their extraction from natural sources. The recent trends in polymer extraction from the natural sources and the scope for the future research of natural polymers in various sectors are also discussed in detail.

Structural and bioactive characteristics of a dextran produced by Lactobacillus kunkeei AK1

In this study, structural and techno-functional characteristics of an exopolysaccharide (EPS) produced by Lactobacillus kunkeei AK1 were determined. High-performance liquid chromatography (HPLC) analysis demonstrated that EPS AK1 was composed of only glucose units. 1H and 13C Nuclear magnetic resonance (NMR) analysis revealed that EPS AK1 was a dextran type EPS containing 4.78% (1 → 4)-linked α-d-glucose branches. The molecular weight of EPS AK1 was determined to be 45 kDa by Gel Permeation Chromatography (GPC) analysis. A high level of thermal stability up to 280 °C was determined for dextran AK1 detected by Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA). Dextran AK1 appeared as regular spheres with compact morphology and as irregular particles in the solution with no clear cross-linking between the chains of the polysaccharide observed by Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) analysis, respectively. X-ray diffraction analysis (XRD) analysis demonstrated that dextran AK1 had a crystalline structure. A relatively strong antioxidant activity was observed for dextran AK1 determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging and cupric reducing antioxidant capacity (CUPRAC) tests. Finally, only a digestion ratio of 3.1% was observed for dextran AK1 following the in vitro simulated gastric digestion test.

High Cyclability Energy Storage Device with Optimized Hydroxyethyl Cellulose-Dextran-Based Polymer Electrolytes: Structural, Electrical and Electrochemical Investigations

The preparation of a dextran (Dex)-hydroxyethyl cellulose (HEC) blend impregnated with ammonium bromide (NH₄Br) is done via the solution cast method. The phases due to crystalline and amorphous regions were separated and used to estimate the degree of crystallinity. The most amorphous blend was discovered to be a blend of 40 wt% Dex and 60 wt% HEC. This polymer blend serves as the channel for ions to be conducted and electrodes separator. The conductivity has been optimized at (1.47 ± 0.12) × 10⁻⁴ S cm⁻¹ with 20 wt% NH₄Br. The EIS plots were fitted with EEC circuits. The DC conductivity against 1000/T follows the Arrhenius model. The highest conducting electrolyte possesses an ionic number density and mobility of 1.58 × 10²¹ cm⁻³ and 6.27 × 10⁻⁷ V⁻¹s⁻¹ cm², respectively. The TNM and LSV investigations were carried out on the highest conducting system. A non-Faradic behavior was predicted from the CV pattern. The fabricated electrical double layer capacitor (EDLC) achieved 8000 cycles, with a specific capacitance, internal resistance, energy density, and power density of 31.7 F g⁻¹, 80 Ω, 3.18 Wh kg⁻¹, and 922.22 W kg⁻¹, respectively.

Low Molar Mass Dextran: One-Step Synthesis With Dextransucrase by Site-Directed Mutagenesis and its Potential of Iron-Loading

Iron dextran is a common anti-anemia drug, and it requires low molar mass dextran as substrate. In this work, we selected 11 amino acid residues in domain A/B of DSR-MΔ2 within a 5-angstrom distance from sucrose for site-directed mutagenesis by molecular docking. Mutation of Q634 did not affect the enzyme catalytic activity, but showed an obvious impact on the ratio of low molecular weight dextran (L-dextran, 3,000–5,000 Da) and relatively higher molecular weight dextran (H-dextran, around 10,000 Da). L-dextran was the main product synthesized by DSR-MΔ2 Q634A, and its average molecular weight was 3,951 Da with a polydispersity index <1.3. The structural characterization of this homopolysaccharide revealed that it was a dextran, with 86.0% α(1→6) and 14.0% α(1→4) glycosidic linkages. Moreover, L-dextran was oxidized with NaOH and chelated with ferric trichloride, and an OL-dextran-iron complex was synthesized with a high iron-loading potential of 33.5% (w/w). Altogether, mutation of amino acids near the sucrose binding site of dextransucrase can affect the chain elongation process, making it possible to modulate dextran size.

Food-Grade Expression and Characterization of a Dextranase from Chaetomium gracile Suitable for Sugarcane Juice Clarification

The microbial production of dextranase using cheap carbon sources is beneficial to solve the economic loss caused by the accumulation of dextran in syrup. A food-grade microbial cell factory was constructed by introducing the dextranase encoding gene DEX from Chaetomium gracile to the chromosome of Bacillus subtilis, and the antibiotic resistance marker gene was subsequently deleted via the Cre/loxP strategy. The dual-promoter system with a sequentially arranged constitutive P43 promoter resulted in an 85 % increase in DEX expression. Under the optimal fermentation conditions of 10 g/L maltose, 15 g/L casein, 1 g/L Na₂ HPO₄ , 1 g/L FeSO₄ and 8 g/L NaCl, DEX activity was increased from 2.625 to 64.34 U/mL. Recombinant DEX was purified 5.98-fold with a recovery ratio of 26.67 % and specific activity of 3935.02 U/mg. Enzyme activity was optimal at 55 °C and pH 5.0 and remained 80.34 % and 71.36 % of the initial activity at 55 °C and pH 4.0 after 60 min, respectively. The enzyme possessed high activity in the presence of Co²⁺ , while Ag⁺ showed the strongest inhibition ability. The optimal substrate was 20 g/L dextran T-2000. The findings could facilitate the low-cost, large-scale production of food-grade DEX for use in the sugar industry.

High-Performance Flocculants for Purification: Solving the Problem of Waste Incineration Bottom Ash and Unpurified Water

The silicon-aluminum-iron flocculant (PAFSi) combines the most abundant resources of waste incineration bottom ash and unpurified water, being regarded as one of the most promising approaches toward water purification. Herein, in this research, waste incineration bottom ash was employed to produce a cost-effective and highly efficient flocculant. PAFSi with a particle size of 214 nm and a zeta potential of 8.63 mV reached the optimum performance using a dosage of 2 mL/50 mL at pH from 8 to 11. The results with the copolymer exhibited the following: (1) a good flocculation efficiency over a wide pH range, (2) superior flocculation performance compared to those of polyaluminum chloride and polyferric sulfate, (3) three-dimensional branching structure of PAFSi micelles with a high aggregation degree, (4) charge neutralization and bridging as the main flocculation mechanism, and (5) recycling the floc. Thus, this work provides an attractive solution to the pressing global clean water shortage problem.

Facile design of a dextran derived polyurethane hydrogel and metallopolymer: a sustainable approach for elimination of organic dyes and reduction of nitrophenols

This work reports a sustainable approach for fabrication of a highly cost-effective and operation-convenient adsorbent derived from dextran and its valorization to a metallopolymer photocatalyst.

Synthesis of polyaluminium chloride/papermaking sludge-based organic polymer composites for removal of disperse yellow and reactive blue by flocculation

In this study, a series of polyaluminium chloride/papermaking sludge-based organic polymer (PAC-PSBF) composites with different PAC basicity and PAC/PSBF mass ratios were prepared from papermaking sludge. The basic properties of the aforementioned composites were characterized, and their flocculation efficiencies were studied in the disperse yellow (DY) and reactive blue (RB) dye removals. The results of the flocculation experiments demonstrated that PAC-PSBF composites performed better than PAC regardless of the PAC basicity or PAC/PSBF mass ratios. The composites with low PAC basicity were effective in DY and RB dye removals. PAC-PSBF composites with the same PAC basicity but higher PAC/PSBF mass ratios exerted more satisfactory color removals and floc properties in both DY and RB dye removals. PAC-PSBF composites were more pH-independent than PAC, and the excellent flocculation efficiencies of the composites was achieved at pH 4.0 to 8.0 in DY/RB dye removals. In brief, desirable flocculation efficiencies of the PAC-PSBF composites were obtained when PAC and PSBF were appropriately combined together.

Evaluation of a novel dextran-based flocculant on treatment of dye wastewater: Effect of kaolin particles

Graft modified flocculants have recently received increasing attention in the field of water treatment as they have the combinative advantages of synthetic and natural polymeric flocculants. In this work, surface-active monomer benzyl(methacryloyloxyethyl)dimethylammonium chloride (BMDAC) was selected to graft on dextran (DX) with high molecular weight (10.3 × 10⁶ g/mol) produced through enzyme-catalyzed process in order to remove dissolved dyes from wastewater. The flocculant (DAB) was fabricated by ultrasound initiated polymerization technique, and the structure characterization of FTIR, ¹H/¹²C NMR, XRD and XPS spectrum confirmed the successful grafting. Then the Congo red (CR) removal efficiency by DAB was optimized based on the flocculation conditions, including wastewater initial pH, flocculant dosage and initial dye concentration. The effect of suspended solids on the removal of dyes was evaluated in kaolin-CR simulated wastewater. The results indicated that the optimal removal efficiency of CR was 68.1% and 88.2% in single CR and kaolin-CR flocculation system, respectively. The improvement of removal efficiency was attributed to the fact that partial CR molecules were adsorbed onto kaolin particles before flocculation, and were synergistically flocculated accompanied by kaolin particles. Finally, the flocculation mechanism was discussed by a detailed investigation of the zeta potentials, FTIR and XPS spectra of flocs, which can provide important reference for optimizing the flocculation conditions and designing novel high-performance flocculants.

Hypocholesterolemic and bioactive potential of exopolysaccharide from a probiotic Enterococcus faecium K1 isolated from kalarei

Bioprospecting of novel probiotic strains especially from unexplored eco-niches has been a continuous practice. Enterococcus faecium K1, an isolate from indigenously fermented milk product kalarei possesses numerous desirable functional attributes. In current study, E. faecium K1 has been used for EPS production, and it yielded 355 ± 0.019 mg/L EPS. EPS demonstrates remarkable hypocholesterolemic, antioxidant, antibiofilm, and emulsification characteristics. EPS is constituted of mannose, glucose and galactose. SEM analysis reveals flake like compact structure of EPS while TEM and X-ray diffractogram confirms the amorphous structure of EPS. FTIR substantiates the functional groups/bonds typical of polysaccharides. Thermal analysis indicates adequate stability of EPS at 237 °C with average weight loss of 22%. E. faecium K1 EPS possesses unique functional bioactivities and physicochemical characteristics, and may potentially be explored for applications in food/pharmaceutical industries.

Synthesis and characterization of dextran-coated iron oxide nanoparticles

Synthesis and characterization of iron oxide nanoparticles coated with a large molar weight dextran for environmental applications are reported. The first experiments involved the synthesis of iron oxide nanoparticles which were coated with dextran at different concentrations. The synthesis was performed by a co-precipitation technique, while the coating of iron oxide nanoparticles was carried out in solution. The obtained nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectrometry, Fourier transform infrared spectroscopy and superconducting quantum interference device magnetometry. The results demonstrated a successful coating of iron oxide nanoparticles with large molar weight dextran, of which agglomeration tendency depended on the amount of dextran in the coating solution. SEM and TEM observations have shown that the iron oxide nanoparticles are of about 7 nm in size.

The effect of NaOH and NaClO/NaBr modification on the structural and physicochemical properties of dextran

Dextran was modified at different pH levels by using NaClO/NaBr and also this method was compared with just using NaOH. Then the properties of the products were investigated.

Purification, characterization, and application of a thermostable dextranase from Talaromyces pinophilus

Abstract

Dextranase can hydrolyze dextran to low-molecular-weight polysaccharides, which have important medical applications. In the study, dextranase-producing strains were screened from various soil sources. The strain H6 was identified as Talaromyces pinophilus by a standard ITS rDNA analysis. Crude dextranase was purified by ammonium sulfate fractionation and Sepharose 6B chromatography, which resulted in a 6.69-fold increase in the specific activity and an 11.27% recovery. The enzyme was 58 kDa, lower than most dextranase, with an optimum temperature of 45 °C and an optimum pH of 6.0, and identified as an endodextranase. It was steady over a pH range from 3.0 to 10.0 and had reasonable thermal stability. The dextranase activity was increased by urea, which enhanced its activity to 115.35% and was conducive to clinical dextran production. Therefore, T. pinophilus H6 dextranase could show its superiority in practical applications.

Graphical Abstract

Fabricating an anionic polyacrylamide (APAM) with an anionic block structure for high turbidity water separation and purification

Ultraviolet (UV)-initiated template polymerization (UTP) was used as a feasible strategy to prepare a novel anionic polyacrylamide (APAM) with a microblock structure.