Renewable bio-based adhesive fabricated from a novel biopolymer and soy protein

In this study, a bio-based soy protein adhesive derived from environmentally friendly and renewable enzymatic hydrolysis lignin (EHL), epoxidized soybean oil (ESO), and soy protein isolate (SPI), was successfully prepared. A novel biopolymer (EHL-ESO), as a multifunctional crosslinker, was firstly synthesized from modified EHL and ESO, and then crosslinked with soy protein isolate to obtain a bio-based soy protein adhesive. The structure, thermal properties, and adhesion performance of the obtained soy protein adhesives were determined by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and wet shear strength. The maximum degradation temperature of SPI/EHL-ESO adhesives (332–343 °C) was higher than that of the pristine SPI adhesive (302 °C). Moreover, plywood bonded by the modified adhesive reached a maximum wet shear strength value of 1.07 MPa, a significant increase of 101.8% from the plywood bonded by pristine SPI adhesive. The enhancements in the thermal stability and wet shear strength were attributed to the formation of a dense crosslinking network structure. This work not only highlights the potential to replace petroleum-based polymers, but also presents a green approach to fabricate fully bio-based soy protein adhesive for preparing all-biomass wood composite materials.

The crosslinking reaction process of SPI/EHL-ESO adhesives.     

Modulating the surface and mechanical properties of textile by oil-in-water emulsion design

The synergistic effect of oil viscosity and oil droplet size on the deposition profile of oil on cotton fabric was studied using polydimethylsiloxane (PDMS) as a model oil-in-water emulsion system. Under the same preparation conditions, low viscosity PDMS produced emulsions containing small droplets, which resulted in a uniform surface deposition profile, whilst high viscosity PDMS resulted in a localised deposition profile. Interfacial phenomena such as wicking and penetration of PDMS into cotton fabrics were found to be viscosity-dependent, which agrees with the surface deposition data. Both mechanical characterisation (friction, compression, stiffness) and consumer evaluation confirm that the fabrics treated by the emulsion containing low viscosity PDMS were preferred, suggesting that a homogeneous surface deposition and an excellent penetration profile of PDMS are critical for maximising tactile sensorial benefits, which could be accomplished by optimising the emulsion formulation to contain oil of low viscosity and small PDMS droplets.

The synergistic effect of oil viscosity and oil droplet size on the deposition profile of oil on cotton fabric was studied using polydimethylsiloxane (PDMS) as a model oil-in-water emulsion system.     

Structural basis for the formation of soy protein nanofibrils

Amyloid-like protein nanofibrils (PNFs) can assemble from a range of different proteins including disease-associated proteins, functional amyloid proteins and several proteins for which the PNFs are neither related to disease nor function. We here examined the core building blocks of PNFs formed by soy proteins. Fibril formation at pH 2 and 90 °C is coupled to peptide hydrolysis which allows isolation of the PNF-forming peptides and identification of them by mass spectrometry. We found five peptides that constitute the main building blocks in soy PNFs, three of them from the protein β-conglycinin and two from the protein glycinin. The abilities of these peptides to form PNFs were addressed by amyloid prediction software and by PNF formation of the corresponding synthetic peptides. Analysis of the structural context in the native soy proteins revealed two structural motifs for the PNF-forming peptides: (i) so-called β-arches and (ii) helical segments involved in quaternary structure contacts. However, the results suggest that neither the native structural motifs nor the protein of origin defines the morphology of the PNFs formed from soy protein isolate.

Identification of the peptide building blocks of soy protein nanofibrils provides new clues about the determinants of protein nanofibril morphology.     

Mechanical and water-resistant properties of rice straw fiberboard bonded with chemically-modified soy protein adhesive

In this work, rice straw and soy protein were used to make fiberboard which may replace wood fiberboard. Soy protein isolates (SPI) were modified by epoxidized oleic acid to improve the soy protein adhesive properties such as adhesion strength and water resistance. The effects of NaOH content, the addition of modified-SPI adhesives and fiberboard density on the mechanical and water-resistant properties of the rice straw fiberboards were investigated. FTIR and XRD results of modified SPI indicated the epoxidized oleic acid and soy protein reacted with each other. FTIR and SEM images of rice straw fibers showed that NaOH solution removed the wax layer through chemical etching. The results of investigating mechanical properties and water absorption illustrate that when the soy protein-based adhesives content and density and the hot pressing temperature and pressure of fiberboard are 12%, 0.8 g cm⁻³, 140 °C and 6 MPa, respectively, the panels have optimal mechanical and water-resistant performances. Moreover, the panels meet the requirements of chinese medium density fiberboard (MDF) Standard of GB/T 11718-2009. Since biological raw materials are recyclable and biomass, the fiberboard bonded with modified soy protein adhesive has no toxicity and is easily biodegradable. In addition, the rice straw burned to produce haze has been preferably utilized.

In this work, rice straw and soy protein were used to make fiberboard which may replace wood fiberboard.     

Improved performance of soy protein adhesive with melamine–urea–formaldehyde prepolymer

In recent years, soy protein adhesive, as an environmentally friendly bio-based adhesive, has attracted extensive attention. In this study, in order to ameliorate the bonding quality of soy protein isolate (SPI) adhesive, the melamine–urea–formaldehyde prepolymer (MUFP) was synthesized, and different amounts of it were introduced into the SPI adhesive as a cross-linking agent. Fourier transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC), thermogravimetric analyze (TGA), and scanning electron microscopy (SEM) were used to analysis the mechanism of modification. The results of plywood test indicated that the wet bonding strength of the adhesives was first increased and then decreased with an increase in the amount of MUFP additive. FT-IR, TGA, and SEM tests suggested that the introduction of MUFP could promote the establishment of a cross-linking structure in the cured adhesive layer to improve the bonding quality of adhesives, but presence of excessive MUFP could introduce hydrophilic groups and adversely affect water resistance.

In recent years, soy protein adhesive, as an environmentally friendly bio-based adhesive, has attracted extensive attention.     

A kinetic model for in situ coking denitrification of heavy oil with high nitrogen content based on starch using a structure-oriented lumping method

In this study, in situ coking denitrification technology was utilized to simplify the entire process by adding an appropriate quantity of denitrification agents to the delayed-coking tower without any further follow-up denitrification process. The effect of starch as the denitrification agent in the in situ coking denitrification process was studied. The distribution of oil products was characterized by GC of simulated distillation. The results indicated that the nitrogen compounds present in heavy oil transformed to coke via in situ coking conversion by reacting with starch. A molecular-level process model for the coking process was developed. Product distribution on the complex reaction network could be described accurately by the model.

In this study, in situ coking denitrification technology was utilized to simplify the entire process by adding an appropriate quantity of denitrification agents to the delayed-coking tower without any further follow-up denitrification process.     

Nanodeformations of microcapsules: comparing the effects of cross-linking and nanoparticles

The mechanical properties of proteinaceous and composite microcapsules loaded with oil were measured by SFM and evaluated using the Reissner model. Comparison of the obtained results reveals significantly higher Young’s moduli of protein capsules due to intermolecular crosslinking. In contrast, conformational restrictions in composite microcapsules inhibit protein crosslinking leading to the reduction of their elasticity.

SFM results for protein and composite microcapsules are evaluated by the Reissner model. Protein capsules show higher Young’s moduli due to crosslinking, which is absent in composite capsules because of restrictions in the protein conformations.     

Correlation between hydrogen yield and product distribution in algae conversion through an isopropanol/water system

This work reports a catalytic decomposition of algae to bio-oil over an isopropanol and water mixture system. The H₂ yield was adjusted by changing the ratio between isopropanol and water. In this system, the introduction of formic acid was helpful to extend the yield range. Five noble metal supported catalysts were applied and Rh/C was proved to give the highest oil yield. A correlation was established between hydrocarbon yield and H₂ yield. It was useful in predicting product distribution and helping to obtain desired products. EA, GC and GC-MS were applied in product analysis.

Catalytic liquefaction of algae to bio-oil through an isopropanol/water system and correlation between hydrogen selectivity and product distribution.     

Preparation and characterization of a soy protein based bio-adhesive crosslinked by waterborne epoxy resin and polyacrylamide

A simple and useful approach by using non-toxic and water-soluble raw material to improve the bonding properties of soy protein adhesive has attracted much attention recently. The objective of this research was to provide a simple and environmentally friendly approach for preparing a high adhesion performance soy protein adhesive in aqueous solution by using waterborne-epoxy resin, soy protein and water-soluble polyacrylamide (PAM). The chemical structure and curing characteristics, as well as the initial viscosity and adhesion performance of the resulted soy protein adhesive were characterized by ¹H nuclear magnetic resonance (¹H-NMR), differential scanning calorimetry (DSC), a rotary viscosity meter and a plywood panel test. The ¹H-NMR analysis results confirmed that epoxy resin was successfully crosslinked with the –NH₂ groups of the soy protein molecule to form a water-resistance network structure, and the resulting adhesive contains active epoxy groups. It was found that the addition of PAM can decrease the apparent viscosity, lower curing temperature, and enhancing the wet shear strength of soy protein adhesives effectively, which were capable of facilitating their application as wood adhesives. The resulting soy protein adhesive containing 4% epoxy resin and 0.05% PAM dosage had a reasonable viscosity and lower cure temperature, and showed good water resistance and wet shear strength, which met the requirement for interior use plywood of the Chinese Industrial Standard. These results suggested that waterborne-epoxy resin can be used to prepare high-performance environmentally friendly soy protein adhesives, which might provide a feasible methodology to prepare bio-adhesive adhesives for plywood industrial applications.

Waterborne epoxy resin mixed with polyacrylamide crosslinked modified soybean protein adhesive.     

Screening of highly effective mixed natural antioxidants to improve the oxidative stability of microalgal DHA-rich oil

Docosahexaenoic acid (DHA)-rich oil sourced from microalgae can easily become oxidized. The objective of this work was to screen the optimal natural antioxidant mixture for protecting DHA-rich oil. Different natural antioxidants, encompassing tea polyphenols, natural vitamin E, rosemary extract, licorice root antioxidant, ascorbyl palmitate and lecithin were tested individually and in combination in an accelerated oxidation process. Three antioxidants namely natural vitamin E, rosemary extract and ascorbyl palmitate with synergistic effects were chosen, and their concentrations were further optimized using response-surface methodology. The highest antioxidants activity of 16.1740 was obtained with a combination of 0.0224% vitamin E, 0.0259% rosemary extract and 0.0166% ascorbyl palmitate, which prolonged the time until oxidation induction to 20.21 days. The mixed natural antioxidants showed a similar antioxidant effect to 0.02% tert-butylhydroquinone and was better than 0.02% butylated hydroxyanisole. These data indicate that the mixed natural antioxidants optimized in this work can be directly applied in the protection of commercial microalgal DHA-rich oil.

Antioxidants with synergistic effect were screened and optimized by RSM. The final natural antioxidant mixture can be actually applied in micrialgal DHA-rich oil, helping to enhance the antioxidant ability of DHA oil and extend its shelf life.     

Preparation and characterization of soy protein isolate-collagen self-assembled nanomicelles

This paper describes the preparation and characterization of soy protein isolate (SPI)-collagen self-assembled nanomicelles. Novel SPI-collagen self-assembled nanomicelles via hydrogen bonding and electrostatic interactions were developed. SPI-collagen soluble complexes were formed at pH 6.4, which was lower than the isoelectric point of collagen (pI = 7.8) and higher than that of SPI (pI = 4.5). This research mainly focuses on the intermolecular force between the SPI and collagen. The diameter distribution, critical association concentration, and stability of the SPI-collagen self-assembled nanomicelles were investigated in this research. It was found that the SPI and collagen had hydrogen bonding and electrostatic interactions, and then formed natural complex nanomicelles in a weakly acidic environment. The preparation of SPI-collagen self-assembled nanomicelles was performed in an aqueous environment without surfactants or toxic agents. As a fixing agent, transglutaminase (TGase) promoted the intra- and intermolecular cross-linking of the nanomicelles, which improved the stability of the self-assembled nanomicelles. The SPI-collagen nanomicelles had a good stability. This research may provide a reference for the utilization of SPI-collagen self-assembled nanomicelles.

This paper describes the preparation and characterization of soy protein isolate (SPI)-collagen self-assembled nanomicelles.     

A novel carboxylic-functional indole-based aerogel for highly effective removal of heavy metals from aqueous solution via synergistic effects of face–point and point–point interactions

A new type of carboxylic-functional indole-based aerogel (CHIFA) has been successfully prepared via a facile sol–gel technology, which possessed a highly effective removal of heavy metals from aqueous solution through the synergistic effects of face–point and point–point interactions.

A new type of carboxylic-functional indole-based aerogel (CHIFA) has been successfully prepared, which possessed highly effective removal of heavy metals from aqueous solution through the synergistic effects of face–point and point–point interactions.     

Effect of water content on the physical properties and structure of walnut oleogels

This study aimed to investigate the effect of water content on the properties and structure of oleogels by developing walnut oleogel based on potato starch and candelilla wax (CW). Physical, thermal, rheological and microstructure characteristics of the walnut oleogel were determined by texture analyzer, differential scanning calorimeter, rotary rheometer, X-ray diffractometer and optical microscope. Results showed that with increased water content, the hardness of the oleogel increased from 123.35 g to 158 g, whereas the oil loss rate decreased from 24.64% to 10.91%. However, these two values decreased slightly when the ratio of oil to water was 1 : 1. The prepared oleogels have a high elastic modulus, and the flow behavior of all walnut oleogels conformed to that of a non-flowing fluid. Microstructure observation indicated that the crystal size and quantity increased with an increase in water content, and the liquid oil was wrapped in the crystal network by CW and potato starch, forming solidified droplets to further promote gelation. In conclusion, when the ratio of oil to water is 39%, the oleogel has good physical properties and stable crystal structure. These findings can provide an indication of water content in the composition of oleogels.

This study aimed to investigate the effect of water content on the properties and structure of oleogels by developing walnut oleogel based on potato starch and candelilla wax (CW).     

Obtention of biodiesel through an enzymatic two-step process. Study of its performance and characteristic emissions

We describe the enzymatic synthesis of biodiesel from waste cooking oil (WCO) in a two-step production process: hydrolysis of WCO, followed by acid-catalyzed esterification of free fatty acids (FFAs). Among the three commercial enzymes evaluated, the inexpensive lipase Lipex® 100L supported on Lewatit® VP OC 1600 produced the best overall biodiesel yield (96.3%). Finally, we assessed the combustion efficiency of the obtained biodiesel and its blends. All blends tested presented lower emissions of CO and HC compared to diesel. The NOx emissions were higher due to biodiesel''s high volatility and viscosity. The cost of biodiesel production was calculated using the process described.

The inexpensive lipase Lipex® 100L produced biodiesel from waste cooking oil in a two-step process, with an overall yield of 96.3%.     

Influence of gardenia yellow on in vitro slow starch digestion and its action mechanism

This study aimed to explore the influence of gardenia yellow on in vitro wheat starch digestion. The influence of gardenia yellow on the digestion properties of starch was determined through in vitro digestion, and its action mechanism on slow starch digestion was revealed by laser scanning confocal microscopy, enzymatic inhibition dynamics, and other means of characterization. Results showed that gardenia yellow could inhibit starch digestion, significantly increase the resistant starch and slowly digestible starch contents in starch (P < 0.05), and trigger the decrease in glycemic and hydrolysis indices. Furthermore, gardenia yellow could spontaneously bind to the catalytic sites of α-amylase and α-glucosidase, affect their secondary structures through vdW force and hydrophobic interaction, and reduce their catalytic abilities to inhibit the digestion process of wheat starch. Therefore, the interactions of gardenia yellow with starch and digestive enzymes jointly promote the slow digestion of starch.

This study aimed to explore the influence of gardenia yellow on in vitro wheat starch digestion.     

Microfiltration of raw soy sauce: membrane fouling mechanisms and characterization of physicochemical,aroma and shelf-life properties

Refinement to remove fermented mash residue is essential for obtaining clarified, stable and high-quality soy sauce. In this study, raw soy sauce microfiltration was investigated. Four widely-used microfiltration membranes were employed: ceramic, polyethersulfone (PES), polyvinylidene fluoride (PVDF) and mixed cellulose ester (MCE). Membrane fouling mechanisms were identified based on the blocking filtration model, indicating that the dominant fouling mechanism during soy sauce microfiltration was cake formation on the membrane surface. Microfiltration delivered highly dispersed soy sauce having superior clarity and a light color, with satisfactory sterilization quality, and preserved well the NaCl, reducing sugar, total acid and amino nitrogen content, leading to a product having a longer shelf life as compared to pasteurization. The loss of volatile compounds after refinement (microfiltration and pasteurization) was not neglected, particularly the ester groups (total loss of 76.3% to 96.4%), which affected the aroma profile of the soy sauce; all the samples from microfiltration seemed to lack the floral aroma. Ceramic membrane filtration and pasteurization exhibited relatively good preservation of the aroma of soy sauce, which then obtained the best scores in sensory analysis.

Membrane fouling mechanisms and characterization of physicochemical, aroma and shelf-life properties of soy sauce subjected to refinement.     

Heavy oil oxidation in the nano-porous medium of synthetic opal

Increasing interest to study hydrocarbon behavior in fine porous media, awakened by the shale revolution, requires the application of suitable model porous media. In the current study we prepared nano-porous synthetic opal, profoundly investigated its morphological and textural properties, and studied the kinetics of combustion of heavy oil impregnated into nanopores. Comparison of kinetic parameters of the oil oxidation process for nano-porous and coarse-porous media revealed that nanoconfinement affects the reactivity of oil.

In the current study we synthesized nano-porous opal, investigated its morphological and textural properties, and showed that nanoconfinement affects reactivity of oil.     

Efficient alkaloid capture from water using a charged porous organic polymer

Berberine hydrochloride (BH), an important alkaloid, can be captured from water and released in organic solution circularly by a charged porous polymer (TPB–HCP), which is hypercross-linked using the cost-effective Friedel–Crafts reaction using sodium tetraphenylborate as the monomer. With high BET surface area, hierarchical porous structure and charged characteristics, TPB–HCP displays excellent adsorption capacity for BH owing to the synergistic effects of size matching and electrostatic interaction.

A charged porous polymer displays excellent adsorption capacity for berberine hydrochloride from the synergistic effects of size matching and electrostatic interaction.     

Highly efficient conversion of CO2 to cyclic carbonates with a binary catalyst system in a microreactor: intensification of “electrophile–nucleophile” synergistic effect

An intensification of the “electrophile–nucleophile” synergistic effect was achieved in a microreactor for the coupling reaction of CO₂ and epoxides mediated by the binary Al complex/ternary ammonium salt catalyst system. The microreactor technology is proven to be a powerful tool for the preparation of cyclic carbonates with an improved reaction rate and a wide substrate scope.

An intensification of the “electrophile–nucleophile” synergistic effect was achieved in a microreactor for the coupling reaction of CO₂ and epoxides mediated by the binary Al complex/ternary ammonium salt catalyst system.     

Bifunctional phase-transfer catalysts for synthesis of 2-oxazolidinones from isocyanates and epoxides

A series of bifunctional phase-transfer catalysts (PTCs) were synthesized to catalyze the [3 + 2] coupling reaction of isocyanates and epoxides to afford 2-oxazolidinones in good to high yields (up to 92% yield) using PhCl as a solvent at 100 °C within 12 h. These bifunctional PTCs were easily prepared from commercially available tertiary-primary diamines and isocyanates (or isothiocyanates, mono-squaramides, respectively) in two simple steps with good modularity and demonstrated high efficiency (2.5 mol% catalyst-loading). The synergistic interaction of the quaternary ammonium salt center and hydrogen-bond donor group in the catalyst with the substrate is crucial to this atom-economic reaction.

A series of bifunctional phase-transfer catalysts were synthesized to catalyze the [3 + 2] coupling reaction of isocyanates and epoxides to afford 2-oxazolidinones in good to high yields (up to 92% yield) using PhCl as a solvent at 100 °C within 12 h.