Da-KGM based GO-reinforced FMBO-loaded aerogels for efficient arsenic removal in aqueous solution

A novel g-C3N4-SH@konjac glucomannan composite aerogel for patulin removal from apple juice and its photocatalytic regeneration

Patulin (PAT) is a hazardous mycotoxin frequently occurs in fruit industry. A reusable g-C3N4-SH@KG composite aerogel for PAT removal in a novel "dark adsorption-light regeneration" mode was prepared by thiol(-SH) functionalization and konjac glucomannan (KG) immobilization. The g-C3N4-SH@KG was characterized by SEM, FT-IR, XPS and UV-Vis DRS, and its PAT adsorption and photocatalytic regeneration behaviors and mechanisms were investigated. The g-C3N4-SH@KG exhibited good regeneration performance, maintaining 83% of PAT initial adsorption capacity (0.92 mg/g) after 5 "adsorption-regeneration" cycles. The adsorption process was endothermic and spontaneous. •OH and h+ generated by photocatalysis were the main substances that degraded PAT into two products and regenerated -SH. The g-C3N4-SH@KG could effectively remove PAT without negative impact on juice quality. The study provided a new strategy for the regeneration of thiol-functionalized PAT adsorbents, and a new idea for the application of non-selective photocatalysis in the control of food contaminations.

Progress of research on aroma absorption mechanism and aroma fixation pathway of jasmine green tea

This overview summarizes the latest research progress on the aroma absorption mechanism and aroma fixation pathway of jasmine green tea, and discusses in depth the aroma absorption mechanism of green tea, the aroma release mechanism of jasmine flowers, as well as the absorption and fixation mechanism of the aroma components of jasmine green tea in the process of scenting, to provide a theoretical basis for the improvement of the quality of jasmine green tea and the innovation of processing technology. It was found that the aroma absorption mechanism of jasmine green tea is mainly associated with both physical and chemical adsorption, aroma release in jasmine involves the phenylpropanoid/benzoin biosynthetic pathway, β-glycosidase enzymes interpreting putative glycosidic groups, and heat shock proteins (HSPs) as molecular chaperones to prevent stress damage in postharvest flowers due to high temperatures and to promote the release of aroma components, and so forth. The preparation of aroma-protein nano-complexes, heat stress microcapsules, and the spraying of polymeric substances - β-cyclodextrin are three examples of aroma-fixing pathways. This overview also summarizes the problems and future development trends of the current research and proposes the method of loading benzyl acetate, the main aroma component of jasmine, through konjac glucomannan (KGM)-based gel to solve the problem of volatile aroma and difficult-to-fix aroma, which provides a reference for the sustainable development of the jasmine green tea industry. © 2024 Society of Chemical Industry.

Diversely regio-oxidative degradation of konjac glucomannan by lytic polysaccharide monooxygenase AA10 and generating antibacterial hydrolysate

Konjac glucomannan (KGM) hydrolysate exhibit various biological activities and health-promoting effects. Lytic polysaccharide monooxygenases (LPMOs) play an important role on enzymatic degradation of recalcitrant polysaccharides to obtain fermentable sugars. It is generally accepted that LPMOs exhibits high substrate specificity and oxidation regioselectivity. Here, a bacteria-derived SmAA10A, with chitin-active with strict C1 oxidation, was used to catalyse KGM degradation. Through ethanol precipitation, two hydrolysed KGM components (4 kDa (KGM-1) and 5 kDa (KGM-2)) were obtained that exhibited antibacterial activity against Staphylococcus aureus. In natural KGM, KGM-1, and KGM-2, the molar ratios of mannose to glucose were 1:2.19, 1:3.05, and 1:2.87, respectively, indicating that SmAA10A preferentially degrades mannose in KGM. Fourier-transform infrared spectroscopy and scanning electron microscopy imaging revealed the breakage of glycosylic bonds during enzymatic catalysis. The regioselectivity of SmAA10A for KGM degradation was determined based on the fragmentation behaviour of the KGM-1 and KGM-2 oligosaccharides and their NaBD4-reduced forms. SmAA10A exhibited diverse oxidation degradation of KGM and generated single C1-, single C4-, and C1/C4-double oxidised oligosaccharide forms. This study provides an alternative method for obtaining KGM degradation components with antibacterial functions and expands the substrate specificity and oxidation regioselectivity of bacterial LPMOs.

Comparative study on the effect of inhibitory methods on the color and gelation properties of alkali induced heat-set konjac gel from Amorphophallus bulbifer

As a newly superior konjac variety, the Amorphophallus bulbifer (A. bulbifer) was easily browning during the alkali-induced process. In this study, five different inhibitory methods, such as citric-acid heat pretreatment (CAT), mixed with citric acid (CA), mixed with ascorbic acid (AA), mixed with L-cysteine (CYS), and mixed with potato starch (PS, containing TiO2), were separately used to inhibit the browning of alkali-induced heat-set A. bulbifer gel (ABG). The color and gelation properties were then investigated and compared. Results showed that the inhibitory methods had significant influences on the appearance, color, physicochemical properties, rheological properties, and microstructures of ABG. Among them, the CAT method not only significantly inhibited the browning of ABG (ΔE value dropped from 25.74 to 14.68) but also improved the water-holding capacity, moisture distribution, and thermal stability without damaging the textural properties of ABG. Moreover, SEM revealed that both CAT and adding PS methods could exhibit the more dense gel network structures of ABG than other methods. It was reasonable to conclude that ABG-CAT offered a superior method to prevent browning compared to the other methods based on the texture, microstructure, color, appearance, and thermal stability of the product.

Konjac Glucomannan Aerogels Modified by Hydrophilic Isocyanate and Expandable Graphite with Excellent Hydrolysis Resistance, Mechanical Strength, and Flame Retardancy

At present, biomass foamlike materials are a hot research topic, but they need to be improved urgently due to their defects such as large size shrinkage rate, poor mechanical strength, and easy hydrolysis. In this study, the novel konjac glucomannan (KGM) composite aerogels modified with hydrophilic isocyanate and expandable graphite were prepared by a facile vacuum freeze-drying method. Compared with the unmodified KGM aerogel, the volume shrinkage of the KGM composite aerogel (KPU-EG) decreased from 36.36 ± 2.47% to 8.64 ± 1.46%. Additionally, the compressive strength increased by 450%, and the secondary repeated compressive strength increased by 1476%. After soaking in water for 28 days, mass retention after hydrolysis of the KPU-EG aerogel increased from 51.26 ± 2.33% to more than 85%. The UL-94 vertical combustion test showed that the KPU-EG aerogel can achieve a V-0 rating, and the limiting oxygen index (LOI) value of the modified aerogel can reach up to 67.3 ± 1.5%. To sum up, the cross-linking modification of hydrophilic isocyanate can significantly improve the mechanical properties, flame retardancy, and hydrolysis resistance of KGM aerogels. We believe that this work can provide excellent hydrolytic resistance and mechanical properties and has broad application prospects in practical packaging, heat insulation, sewage treatment, and other aspects.

Evaluation of the composition of konjac glucomannan on the color changes during the deacetylation reaction

As a newly superior konjac variety, the Amorphophallus bulbifer (A. bulbifer) has several unique advantages of high reproductive coefficient, short growth cycle, high disease resistance, high konjac glucomannan (KGM) content and climate adaption to hot or humid conditions. However, the gel formed by KGM from the A. bulbifer flour is easily browning during the alkali-induced process and the mechanism underlying them is still unclear. In order to explore the browning mechanisms, the changes of composition and color parameters of KGM were investigated during deacetylation in this research. The L*, h*, total phenols, total flavonoids, reducing sugars, and amino acids decreased along with the increase of deacetylation degree of KGM while a*, ΔЕ, and browning index increased. The results indicated that the oxidation or polymerization of polyphenols and flavones in alkaline circumstances, and the carbonyl ammonia reaction between reducing sugars and amino acids may be the main reasons for color changes of KGM flour during deacetylation. Hence, this study was expected to provide the theoretical basis for the inhibition of KGM gel browning and further broaden the application range of KGM in food and other industries.

Adsorption performance and its mechanism of aqueous As(III) on polyporous calcined oyster shell-supported Fe-Mn binary oxide

Fe-Mn binary oxide (FMBO) is a promising adsorbent for As(III) removal through combined adsorption and oxidation. The calcined oyster shell-supported Fe-Mn binary oxide (FMBO/OS) adsorbent was synthesized by the co-precipitation method. Results indicated that the calcined oyster shell, as a carrier, improved the stability of FMBO and its adsorption capacity for As(III). The maximum adsorption capacity of FMBO/OS on As(III) reached 140.5 mg·g^-1 . Under pH 5.0 and 25°C, the removal efficiency of FMBO/OS to As(III) solution (C₀  = 10 mg·L^-1 ) reached 87% within 12 h. Moreover, based on the characterization analyses, the removal mechanisms of As(III) were deduced to include the combined adsorption and oxidation process of FMBO and the synergistic effect of oyster shells. This work provides new insights into synthesizing efficient and green adsorbents to remove aqueous As(III). Meanwhile, it provides technical support for reusing waste biomass materials such as the oyster shell. PRACTITIONER POINTS: FMBO/OS was prepared by a simple hydrothermal co-precipitation method. The carrier alleviates the agglomeration of Fe-Mn oxides. The adsorbent shows a strong adsorption capacity of As(III) and good selectivity. The good results benefit from the synergistic effect of calcium arsenate generation. The prepared adsorbent can adsorb arsenic in real samples.

Review on heterogeneous oxidation and adsorption for arsenic removal from drinking water

The long term exposure of arsenic via drinking water has resulted in wide occurrence of arsenisim globally, and the oxidation of the non-ionic arsenite (As(III)) to negatively-charged arsenate (As(V)) is of crucial importance for the promising removal of arsenic. The chemical oxidants of ozone, chlorine, chlorine dioxide, and potassium permanganate may achieve this goal; however, their application in developing countries is sometimes restricted by the complicate operation and high cost. This review paper focuses on the heterogeneous oxidation of As(III) by solid oxidants such as manganese oxide, and the adsorption of As(V) accordingly. Manganese oxide may be prepared by both chemical and biological methods to achieve good oxidation performance towards As(III). Additionally, manganese oxide may be combined with other metal oxides, e.g., iron oxide, to improve the adsorption capability towards As(V). Furthermore, manganese oxide may be coated onto porous materials of metal organic frameworks to develop novel adsorbents for arsenic removal. To achieve the application in engineering works, the adsorbents granulation may be achieved by drying and calcination, agglomeration, and the active components may also be in situ coated onto the porous materials to maintain the oxidation and adsorption activities as much as possible. The novel adsorbents with heterogeneous oxidation and adsorption capability may be carefully designed for the removal of arsenic in household purifiers, community-level decentralized small systems, and the large-scale drinking water treatment plants (DWTPs). This review provides insight into the fundamental studies on novel adsorbents, the development of innovative technologies, and the demonstration engineering works involved in the heterogeneous oxidation and adsorption, and may be practically valuable for the arsenic pollution control globally.

Effect of ultrasound assisted konjac glucomannan treatment on properties of chicken plasma protein gelation

The effect of ultrasound assisted konjac glucomannan treatment on the properties of chicken plasma protein gelation was investigated in this study. There were four gelation groups as follows: untreated plasma protein gelation (Control), gelation added konjac glucomannan (KGG), gelation by ultrasound treatment alone (UG) and gelation added konjac glucomannan combined with ultrasound treatment (KGUG). The data showed that the gelation strength and water-holding capacity of the treated groups were significantly increased compared with those of Control. The strongest bonding water was present in KGUG, followed by KGG and UG in low-field nuclear magnetic resonance. The storage energy (G') and loss energy modulus (G″) of KGUG showed the largest rheological properties, and the G' value was higher than that of G″. Furthermore, the elastic and gelatinous properties of UG, KGG and KGUG played a dominant role in viscoelasticity. After konjac glucomannan addition, the particle size of KGG increased significantly. Compared with that of the Control and KGG, the average particle size of UG and KGUG decreased significantly after ultrasound treatment. The hydrophobicity and disulfide bonds mainly affected the formation of heat-induced gelation in these four groups. Furthermore, KGUG with the highest hydrophobicity and disulfide bonds revealed the best stability. Therefore, the gelation of chicken plasma protein by ultrasound assisted konjac glucomannan treatment had excellent gelling properties.

Removal of decidedly lethal metal arsenic from water using metal organic frameworks: a critical review

Water contamination is worldwide issue, undermining whole biosphere, influencing life of a large number of individuals all over the world. Water contamination is one of the chief worldwide danger issues for death, sickness, and constant decrease of accessible drinkable water around the world. Among the others, presence of arsenic, is considered as the most widely recognized lethal contaminant in water bodies and poses a serious threat not exclusively to humans but also towards aquatic lives. Hence, steps must be taken to decrease quantity of arsenic in water to permissible limits. Recently, metal-organic frameworks (MOFs) with outstanding stability, sorption capacities, and ecofriendly performance have empowered enormous improvements in capturing substantial metal particles. MOFs have been affirmed as good performance adsorbents for arsenic removal having extended surface area and displayed remarkable results as reported in literature. In this review we look at MOFs which have been recently produced and considered for potential applications in arsenic metal expulsion. We have delivered a summary of up-to-date abilities as well as significant characteristics of MOFs used for this removal. In this review conventional and advanced materials applied to treat water by adsorptive method are also discussed briefly.

Effect of konjac glucomannan/carrageenan-based edible emulsion coatings with camellia oil on quality and shelf-life of chicken meat

The quality and safety of chicken meat are prone to deteriorate due to bacteria reproduction and oxidation reaction. In this study, the antimicrobial and antioxidant effects of KGM-KC coatings incorporated camellia oil were evaluated to extend the shelf-life of chicken meat. The result showed that the KGM/KC-CO coating significantly (P < 0.05) decreased weight loss, pH, thiobarbituric acid reactive substance (TBARS), total volatile nitrogen (TVN) and microbial counts when compared to uncoated samples. The obtained results revealed that KGM/KC-based coating incorporated with CO significantly extended the shelf-life of chicken meat by restraining the oxidation of lipid and protein, and retarding the microbial growth. The sensory evaluation showed that the addition of CO did not affect the odor of chicken meat, maintained the overall acceptability of coated samples. The shelf-life of chicken meat was extended up to 10 days using KGM/KC-based coating containing 3.5% CO at refrigeration (4 °C) compared to control samples. These results indicated CO could be used as an active agent to be dispersed in KGM/KC matrix by emulsification method, and the prepared emulsion coating had positive effects on extending the shelf-life of chicken meat.

Application of three dimensional porous aerogels as adsorbent for removal of heavy metal ions from water/wastewater: A review study

Nowadays, by rapid development of economies and industries, water contamination through the heavy metal ions (toxic, non-toxic and radioactive) is a great concern and an important environmental problem. Currently, numerous techniques such as chemical precipitation, coagulation, ion-exchange, filtration, reverse osmosis, biological treatment and physical adsorption are presented by researchers for removing and recycling heavy metal ions from wastewater. Among these methods, adsorption approach is one of the most efficient techniques for the elimination of heavy metal ions from aqueous solutions. There are a number of low cost absorbent such as agricultural and industrial solid waste such as lingo-cellulosic materials, wheat bran, peanut shell, moss peat, fly ash, bagasse, tree fern, gram husk, nanostructures (such as TiO₂, SiO₂, SnO₂, ZnO, etc.), 3D porous structures (aerogels), etc. which have been developed and tested to efficient removal of heavy metal ions from wastewater. In this study, a critical review of the applications of aerogels in water and sewage purifications is performed. For this reason, different kinds of aerogel namely organic, inorganic and organic-inorganic hybrid aerogels are investigated. It is concluded that the most applicable aerogels used in these studies are graphene-based aerogels due to more porous structure as well as simplification of their modification. Also, in this review paper, for the first time we summarized and highlighted the recent literature information about heavy metal ions and theirs removal methods from aqueous pollutants and wastewater/water, adsorption kinetics, isotherms and thermodynamics models by different type of three dimensional (3D) porous structure. In additional, in this review article, the influence of various parameters such as pH solution, temperature, initial concentration of heavy metal ions, composition, contact time, coexisting ions and adsorbent dosage on the adsorption process of heavy metal ions were investigated.

Carboxymethyl konjac glucomannan mechanically reinforcing gellan gum microspheres for uranium removal

Biosorbents have been a promising adsorbent to remove uranium while their poor mechanical properties prevent them from being widely used in practice. In this study, carboxymethyl konjac glucomannan (CMKGM) was incorporated to gellan gum to form a double-network gel micro spheres (CMKGM/GG-Al) for uranium removal with its mechanical strength fairly being reinforced. The compressive strength of the CMKGM/GG-Al microspheres was about 6 times than that of GG-Ca microspheres we prepared before while the adsorption capacity still be at a better value with the fitting maximum adsorption capacity being of 97.94 mg/g. Its uranium adsorption properties were investigated by considering the influence of pH, the adsorbent dosage, temperature, initial uranium concentration, time and coexisting ions. The adsorption mechanism was also investigated according to the SEM, EDX, FT-IR and XPS data analysis. The isotherm equilibrium data which were best fitted with Langmuir model and the kinetics data which were best fitted with pseudo-second-order model. It was inferred that the adsorption process was mainly the ion-exchange and the coordination with hydroxyl groups on the adsorbent surface and the adsorption process was endothermic and spontaneous. The CMKGM/GG-Al microspheres prepared in this study would be more conducive to practical application for uranium removal.

Microfluidic spinning of poly (methyl methacrylate)/konjac glucomannan active food packaging films based on hydrophilic/hydrophobic strategy

Here, inspired by the hydrophilic/hydrophobic theory, a novel konjac glucomannan/poly (methyl methacrylate)/chlorogenic acid (KGM/PMMA/CGA) food packaging film was successfully fabricated via microfluidic spinning technology (MST). The results of fourier transform infrared spectroscopy and x-ray diffraction confirmed the formation of hydrogen bonds in the films, which lead to the enhanced mechanical properties. Thermogravimetric analysis and differential scanning calorimetry showed excellent thermal stability of the films. Water vapor permeability (1.47 × 10^-5 ± 0.11 g/(m⋅h⋅kPa)) and water contact angle (89.2°) measurement proved that the films were hydrophobic. The good swelling degree (85.18 ± 15.65%) indicated film's potentials in releasing CGA. More importantly, KGM played a key role in the antibacterial activities against Staphylococcus aureus (8.5 ± 3.5 mm) and Escherichia coli (6.5 ± 2.1 mm) by utilizing its hydrophilicity. Thus, our present work may provide a new idea for constructing active food packaging films with significant performances based on hydrophilic/hydrophobic strategy.

Mussel-inspired fabrication of konjac glucomannan/microcrystalline cellulose intelligent hydrogel with pH-responsive sustained release behavior

Intelligent hydrogels are attractive biomaterials for various applications, however, fabricating a hydrogel with both adequate self-healing ability and mechanical properties remains a challenge. Herein, a series of novel intelligent konjac glucomannan (KGM)/microcrystalline cellulose (MCC) hydrogels were prepared vis the mussel-inspired chemistry. MCC was firstly functionalized by the oxidative polymerization of dopamine, and the intelligent hydrogels were obtained by mixing aqueous solutions of KGM and functionalized MCC (PDMCC). By introducing PDMCC, a more compact interconnected porous structure formed for the resulting hydrogels. The self-healing ability and mechanical properties of intelligent hydrogels were dependence on the PDMCC content. Compared with KGM hydrogels, KGM/PDMCC hydrogels exhibited a more distinct pH sensitivity and a lower initial burst release, which was attributed to the compact structure and strong intermolecular hydrogen bond interaction between PDMCC and KGM. These results suggest that the KGM/PDMCC intelligent hydrogels may be promising carriers for controlled drug delivery.

A Review on Konjac Glucomannan Gels: Microstructure and Application

Konjac glucomannan (KGM) has attracted extensive attention because of its biodegradable, non-toxic, harmless, and biocompatible features. Its gelation performance is one of its most significant characteristics and enables wide applications of KGM gels in food, chemical, pharmaceutical, materials, and other fields. Herein, different preparation methods of KGM gels and their microstructures were reviewed. In addition, KGM applications have been theoretically modeled for future uses.