Eco-friendly/Sustainable Approach to Polysaccharides as (nano) materials

Methyl cellulose and its derivatives are widely used in the food industry, cosmetics, and as construction materials. The properties of methyl celluloses (MC) strongly depend on their degrees and positions of substitution. In order to generate MCs with uncommon blocky substitution, we apply fully protected O-benzyl-O-methyl celluloses (BnMC). Such complex polysaccharide derivatives could not be deprotected completely and without shift of the composition by methods usually applied to mono- and oligosaccharides. Therefore, a facile debenzylation method was developed based on photo-initiated free-radical bromination in the presence of hydrobromic acid scavengers followed by alkaline treatment. The reaction proceeds under homogeneous conditions and without the aid of any catalyst. There is no need for expensive equipment, materials, anhydrous reagents, or running the reaction under anhydrous conditions. Reaction parameters were investigated and optimized for successful debenzylation of completely protected BnMC with degrees of methyl substitution (DS_Me) around 1.9 (and DS_Bn around 1.1). Side-product-free and almost complete debenzylation was achieved when 1,2-epoxybutane (0.5 eq./eq. N-bromosuccinimide) and 2,6-di-tert-butylpyridine (0.5 eq./eq. N-bromosuccinimide) were used in the reaction. Furthermore, ATR-IR and ¹H NMR spectroscopy confirmed the successful removal of benzyl ether groups. The method was developed to monitor the transglycosylation reaction of the BnMC with permethylated cellulose, for which the deprotection of many small samples in parallel is required. This comprises the determination of the methyl pattern in the glucosyl units by gas-liquid chromatography (GLC), as well as oligosaccharide analysis by liquid chromatography mass spectrometry (LC-MS) after perdeuteromethylation and partial hydrolysis to determine the methyl pattern in the chains. The unavoidable partial chain degradation during debenzylation does not interfere with this analytical application, but, most importantly, the DS and the methyl pattern were almost congruent for the debenzylated product and the original MC, indicating the full success of this approach The presented method provides an unprecedented opportunity for high throughput and parallel debenzylation of complicated glucans, such as BnMC (as a model compound), for analytical purposes. For comparison, debenzylation using Na/NH₃ was applied to BnMC and resulted in a completely debenzylated product with a remarkably high recovery yield of 99 mol% and is, thus, the method of choice for synthetic applications, e.g., for the transglycosylation product prepared under the selected conditions in a preparative scale. Full article

Orange bagasse (OB) could be considered a sustainable, renewable, and low-cost biomass for the extraction of cellulose. In this context, reactive extrusion can be considered an excellent, eco-friendly, alternative process for the extraction of cellulose from lignocellulosic materials. Thus, the present study aimed to obtain cellulose-based materials with a reactive extrusion process and also to investigate the impact of pectin on the delignification process. Two groups of samples (OB and depectinizated OB) were submitted to extrusion with sulfuric acid or sodium hydroxide in one-step processes. The cellulose content of extruded materials was highly affected by pectin content in the raw material; the thermal profile (TGA curves) and crystallinity also changed. The cellulose content of modified materials ranged from 18.8% to 58.4%, with a process yield of 30.6% to 79.2%. The alkaline reagent provided the highest cellulose content among all extrusion treatments tested, mainly for OB without pectin. The extrusion process was considered an efficient and promising process for extracting cellulose from citrus residue. Materials produced in this study can be used as sources of cellulose fiber for various products and processes, such as in the food industry, fermentation substrates, or refined applications after subsequent treatments. Full article

The human-made pollution of surface and ground waters is becoming an inevitable and persistently urgent problem for humankind and life in general, as these pollutants are also distributed by their natural circulation. For example, from mining activities and metallurgy, toxic heavy metals pollute the environment and present material risk for human health and the environment. Bioadsorbers are an intriguing way to efficiently capture and eliminate these hazards, as they are environmentally friendly, cheap, abundant, and efficient. In this study, we present brewers’ spent grain (BSG) as an efficient adsorber for toxic heavy metal ions, based on the examples of iron, manganese, cadmium, and nickel ions. We uncover the adsorption properties of two different BSGs and investigate thoroughly their chemical and physical properties as well as their efficiency as adsorbers for simulated and real surface waters. As a result, we found that the adsorption behavior of BSG types differs despite almost identical chemistry. Elemental mapping reveals that all components of BSG contribute to the adsorption. Further, both types are not only able to purify water to reach acceptable levels of cleanness, but also yield outstanding adsorption performance for iron ions of 0.2 mmol/g and for manganese, cadmium, and nickel ions of 0.1 mmol/g. Full article

Nowadays, the scientific interest is focused more and more on the development of new strategies in recycling of waste products as well as on the development of clean technologies due to the increased environmental pollution. In this work we studied the valorization of an expired cheese-tomato flavor corn snack, which is polysaccharide food product, by producing advanced hybrid magnetic materials for environmental remediation purposes. The carbonization-chemical activation of this snack using potassium hydroxide leads to a microporous activated carbon with high surface area (S_gBET ~800 m²/g). The magnetic hybrid material was synthesized via an in-situ technique using iron acetate complex as the precursor to produce iron based magnetic nanoparticles. The resulting material retains a fraction of the microporous structure with surface area S_gBET ~500 m²/g. Such material consists, of homogenously dispersed magnetic isolated zero valent iron nanoparticles and of iron carbides (Fe₃C), into the carbon matrix. The magnetic carbon exhibited high adsorption capacity in Cr(VI) removal applications following a pseudosecond order kinetic model. The maximum adsorption capacity was 88.382 mg_Cr(VI)/g_AC at pH = 3. Finally, oxidation experiments, in combination with FT-IR, Mössbauer, and VSM measurements indicated that the possible Cr⁶⁺ removal mechanism involves oxidation of iron phases and reduction of Cr⁶⁺ to Cr³⁺. Full article

Cellulose is a natural, unbranched, and fibrous homopolymer that is a major component in several agroindustrial residues. The aim of this study was to extract cellulose from oat hulls and then to modify it using a green route to obtain esterified cellulose through reaction with organic acids employing the reactive extrusion process, which is a process that presents some advantages, including low effluent generation, short reaction times, and it is scalable for large scale use. Citric (CA) and succinic (SA) acids were employed as esterifying agents in different concentrations (0, 5, 12.5, and 20%). Modified cellulose samples were characterized by their degree of substitution (DS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (DRX), scanning electron microscopy (SEM), wettability, oil and water absorption capacities, and thermal stability. DS of modified samples ranged from 2.28 to 3.00, and FTIR results showed that the esterification occurred in all samples for both acids by observation of important bands at 1720 and 1737 cm⁻¹ for samples modified with CA and SA, respectively. All modified samples presented increased hydrophobicity. The modification did not have an influence on the morphological structure or crystallinity pattern of all samples. This study proved to be possible to modify cellulose using a simple and ecofriendly process based on reactive extrusion with organic acids. Full article

Grape processing residues are a good source of bioactive and nutritional compounds. The incorporation of grape pomace extract (GPE) in starch films can be a strategy for the elaboration of new food packaging products for applications such as edible films or fruit strips. In this context, the objective of this research was to analyze the effect of incorporation and variation of concentration of GPE (0, 20, 30, and 40% mass/mass starch solids) on the physical chemical properties of arrowroot starch edible films created by casting. The GPE was characterized for moisture content, pH, total titratable acidity, total soluble solids, and anthocyanin content. Starch films with and without GPE were evaluated by analyzing their visual appearance, water activity, water content, thickness, water solubility, and water vapor permeability. The GPE had high water content, acidity, and anthocyanins content. The films with GPE showed a noticeable reddish color, similar to observed for the GPE. Increasing the concentration of GPE in the film resulted in significantly increased (p < 0.05) thickness (from 0.060 to 0.106 mm), water content (from 8.17 to 12.48%), solubility in water (from 13.33 to 33.32%), and water vapor permeability (from 3.72 to 6.65 g.mm/m² day kPa). GPE increased the hydrophilic portion of the film, in addition to acting as a plasticizer, decreasing the molecular interactions of the polymer chain, and favoring its solubilization, which is desirable for applications such as edible films. The elaboration of arrowroot starch films with the incorporation of grape pomace is a good alternative for the reduction of by-products of grape processing. Full article

Cardamom essential oil (EO) is a rare oil of high scientific and economic interest due to its biofunctionality. This work aims to stabilize the EO by Pickering emulsions with nanocellulose, in the form of nanocrystals (CNC) or nanofibers (CNF), and to investigate the stability and chemical and physical interactions involved in the process. The emulsions were characterized by droplet size, morphology, stability, surface charges, Fourier transform infrared spectroscopy, FT-Raman, nuclear magnetic resonance, and scanning electron microscopy. Stable emulsions were prepared with cellulose morphologies and CNCs resulted in a 34% creaming index, while CNFs do not show instability. Emulsions indicate a possible interaction between nanocellulose, α-terpinyl acetate, and 1,8-cineole active essential oil compounds, where α-terpinyl acetate would be inside the drop and 1,8-cineole is more available to interact with cellulose. The interaction intensity depended on the morphology, which might be due to the nanocellulose’s self-assembly around oil droplets and influence on oil availability and future application. This work provides a systematic picture of cardamomum derived essential oil Pickering emulsion containing nanocellulose stabilizers’ formation and stability, which can further be extended to other value-added oils and can be an alternative for the delivery of cardamom essential oil for biomedical, food, cosmetics, and other industries. Full article

Calcium chloride (CaCl₂) has been widely used to maintain the quality of fresh-cut fruits and vegetables because it stabilizes and strengthens the membrane system against fungal attacks. It is mainly applied via spray coating and dip coating techniques. This study explored a method of incorporating calcium chloride extracted from eggshells in a packaging material, thermoplastic starch (TPS), via a hot-melt extrusion process. The composites were characterized by FTIR, DSC, SEM-EDX and tensile testing. FTIR confirmed the chemical reactions between CaCl₂ and TPS. DSC results showed a significant decrease in the heat of fusion by adding 20 wt% of CaCl₂ content in TPS, indicating a drop in the degree of crystallinity. The Young’s modulus of TPS was not significantly affected by the incorporation of 10 wt% CaCl₂ (P = 0.968), but reduced notably with the addition of 20 wt% CaCl₂ (P = 0.05), indicating the plasticizer effect of the CaCl₂. Physiochemical analysis of fresh-cut apple slices was assessed. Samples placed on the surface of the TPS/CaCl₂ composites displayed less pH reduction, reduced antioxidant activity, more weight loss and increased reducing sugar compared to the samples placed on the surface of virgin TPS films. CaCl₂ released from the TPS/CaCl₂ films was measured and their antimicrobial activity was confirmed by bacterial inhibitory growth assessment. Fungal growth was observed on apple slices placed on virgin TPS film by day 21 while apple slices placed on TPS/CaCl₂ 20 wt% composites did not support any fungal growth for 28 days. In summary, TPS and eggshell-extracted CaCl₂ showed the ability to maintain the quality of fresh-cut apples, and TPS/CaCl₂ 10 wt% composite could be a good option as a packaging material for fresh-cut fruits due to active antimicrobial activity and maintained Young’s modulus. Full article

Development of biodegradable materials for packaging is an issue of the utmost importance. These materials are an alternative to petroleum-based polymers, which contribute to environment pollution after disposal. In this work, graphene oxide (GO) and glucose-reduced graphene oxide (rGO-g) were incorporated to thermoplastic starch (TPS) by melt extrusion. The TPS/GO and TPS/rGO-g composites had their physical properties and biodegradability compared. X-ray diffraction (XRD) showed that the type of graphene used led to different dispersion levels of graphene sheets, and to changes in the crystalline structure of TPS. Tensile tests carried out for the compression-molded composites indicated that TPS/rGO-g composites presented better mechanical performance. The Young’s modulus (E) increased from E = (28.6 ± 2.7) MPa, for TPS, to E = (110.6 ± 9.5) MPa and to (144.2 ± 11.2) MPa for TPS with rGO-g incorporated at 1.0 and 2.0 mass% content, respectively. The acid groups from graphene derivatives promoted glycosidic bond breakage of starch molecules and improved biodegradation of the composites. GO is well-dispersed in the TPS matrix, which contributes to biodegradation. For TPS/rGO-g materials, biodegradation was influenced by rGO-g dispersion level. Full article

Several studies report the potential of bacterial cellulose (BC) in the fashion and leather industries. This work aimed at the development of BC-based composites containing emulsified acrylated epoxidized soybean oil (AESO) that are polymerized with the redox initiator system hydrogen peroxide (H₂O₂) and L-ascorbic acid and ferrous sulfate as a catalyst. BC was fermented under static culture. The polymerization of the emulsified organic droplets was tested before and after their incorporation into BC by exhaustion. The composites were then finished with an antimicrobial agent (benzalkonium chloride) and dyed. The obtained composites were characterized in terms of wettability, water vapor permeability (WVP), mechanical, thermal and antimicrobial properties. When AESO emulsion was polymerized prior to the exhaustion process, the obtained composites showed higher WVP, tensile strength and thermal stability. Meanwhile, post-exhaustion polymerized AESO conferred the composite higher hydrophobicity and elongation. The composites finished with the antimicrobial agent showed activity against S. aureus. Finally, intense colors were obtained more uniformly when they were incorporated simultaneously with the emulsified AESO with all the dyes tested. Full article

The separation of toxic pollutants such as Pb²⁺, Cd²⁺, and Al³⁺ from water is a constant challenge as contamination of natural water bodies is increasing. Al³⁺ and especially Pb²⁺ and Cd²⁺ are ecotoxic and highly toxic for humans, even in ppb concentrations, and therefore removal below a dangerous level is demanding. Herein, the potential adsorber material starch, being ecofriendly, cheap, and abundantly available, was investigated. Thus, four different native starch samples (potato, corn, waxy corn, and wheat starch) and two oxidized starches (oxidized potato and corn starch) were comprehensively analyzed with streaming potential and charge density measurements, SEM-EDX, ATR-FTIR, ¹H-NMR, and TGA. Subsequently, the starch samples were tested for the adsorption of Pb²⁺, Cd²⁺, and Al³⁺ from the respective sulfate salt solution. The adsorption process was analyzed by ICP-OES and SEM-EDX, and the adsorption isotherms were fitted comparing Langmuir, Sips, and Dubinin-Radushkevich models. Oxidized starch, for which chemical modification is one of the simplest, and also native potato starch were excellent natural adsorber materials for Al³⁺, Cd²⁺, and especially Pb²⁺ in the low concentration range, exhibiting maximum adsorption capacities of 84, 71, and 104 µmol/g for oxidized potato starch, respectively. Full article

Agave, commonly known as “maguey” is an important part of the Mexican tradition and economy, and is mainly used for the production of alcoholic beverages, such as tequila. Industrial exploitation generates by-products, including leaves, bagasse, and fibers, that can be re-valorized. Agave is composed of cellulose, hemicellulose, lignin, fructans, and pectin, as well as simple carbohydrates. Regarding functional properties, fructans content makes agave a potential source of prebiotics with the capability to lower blood glucose and enhance lipid homeostasis when it is incorporated as a prebiotic ingredient in cookies and granola bars. Agave also has phytochemicals, such as saponins and flavonoids, conferring anti-inflammatory, antioxidant, antimicrobial, and anticancer properties, among other benefits. Agave fibers are used for polymer-based composite reinforcement and elaboration, due to their thermo-mechanical properties. Agave bagasse is considered a promising biofuel feedstock, attributed to its high-water efficiency and biomass productivity, as well as its high carbohydrate content. The optimization of physical and chemical pretreatments, enzymatic saccharification and fermentation are key for biofuel production. Emerging technologies, such as ultrasound, can provide an alternative to current pretreatment processes. In conclusion, agaves are a rich source of by-products with a wide range of potential industrial applications, therefore novel processing methods are being explored for a sustainable re-valorization of these residues. Full article

Polysaccharide biomaterials have gained significant importance in the manufacture of nanoparticles used in colon-targeted drug delivery systems. These systems are a form of non-invasive oral therapy used in the treatment of various diseases. To achieve successful colonic delivery, the chemical, enzymatic and mucoadhesive barriers within the gastrointestinal (GI) tract must be analyzed. This will allow for the nanomaterials to cross these barriers and reach the colon. This review provides information on the development of nanoparticles made from various polysaccharides, which can overcome multiple barriers along the GI tract and affect encapsulation efficiency, drug protection, and release mechanisms upon arrival in the colon. Also, there is information disclosed about the size of the nanoparticles that are usually involved in the mechanisms of diffusion through the barriers in the GI tract, which may influence early drug degradation and release in the digestive tract. Full article