High Molecular Weight Material Research Articles

The Laccase Catalysed Tandem Lignin Depolymerisation/Polymerisation.

The development of strategies allowing either the production of high value phenolics, or the isolation of properties-enhanced materials from technical lignins represents a fundamental step in the industrial upcycling of technical lignins. Both aims are met by the strategy presented in the present work, relying on the coupling of solvent-based fractionation with the oxidative action of a new type of alkaline-stable genetically modified bacterial laccase. The described approach succeeded in the tandem, high-yield and selective isolation of valuable lignin-monomeric compounds (MCs) and high molecular weight and hydrophobicity-tailored polymerised materials (PMs) from two technical lignins, namely softwood kraft lignin (SKL), and wheat straw organosolv lignin (WSL). With respect to MCs, higher yields as compared to similar studies (up to 17.2 mg/g) were achieved. PMs from SKL samples where characterised by an almost quadrupled Mw, while in the case of WSL the Mw was approximately doubled. Noteworthy, the reaction conditions were optimized in terms of reaction temperature, time, enzymatic loading, and alkalinity for the selective production of single MCs. Most interestingly, technical lignins as well as their fractions and the PMs deriving from their laccase-catalysed oxidation showed increased hydrophobicity.

State diagrams of green peas (Pisum sativum L.) powders with different maltodextrin additions.

The purpose of this study was to examine the effect of maltodextrin addition on the physical stability of powdered green peas. The evaluation of the physical state of the material was based on the equilibrium water content of the monolayer (Xm) and the glass transition temperatures of the powders at room temperature (Tg) and in the frozen state (Tg'). Graphical sorption characteristic at 25°C was determined using static-gravimetric method while capacity of the monolayer values was calculated from the mathematical GAB model. Differential scanning calorimetry was carried out in order to determine glass transition lines and freezing curves which combine together were used to plot state diagrams. Relationship between Tg and solid content were shown by using Gordon-Taylor model. Freezing data were modeled employing the Clausius-Clapeyron equation and its development-Chen model. Sorption isotherms showed sigmoidal shape characteristic for high-molecular weight materials. Monolayer moisture content varied between 0.047 and 0.106 g water/g solids. The glass transition temperature of anhydrous green peas increased in from 89.9 to 175.6°C while Tg' value changed from -43.4 to -26.6°C to as a result of 75% polysaccharide addition. The ultimate maximum-freeze-concentration conditions of the powders were observed in range from 0.783 to 0.814 g solids/g sample. Monolayer capacity, Tg and Tg' values increased with increasing maltodextrin amount in the sample which indicates that the addition of starch hydrolysate has a beneficial effect on the stability of powders stored frozen and at room temperature.

Dominant heterocyclic composition of dissolved organic nitrogen in the ocean: A new paradigm for cycling and persistence.

Marine dissolved organic nitrogen (DON) is one of the planet's largest reservoirs of fixed N, which persists even in the N-limited oligotrophic surface ocean. The vast majority of the ocean's total DON reservoir is refractory (RDON), primarily composed of low molecular weight (LMW) compounds in the subsurface and deep sea. However, the composition of this major N pool, as well as the reasons for its accumulation and persistence, are not understood. Past characterization of the analytically more tractable, but quantitatively minor, high molecular weight (HMW) DON fraction revealed a functionally simple amide-dominated composition. While extensive work in the past two decades has revealed enormous complexity and structural diversity in LMW dissolved organic carbon, no efforts have specifically targeted LMW nitrogenous molecules. Here, we report the first coupled isotopic and solid-state NMR structural analysis of LMW DON isolated throughout the water column in two ocean basins. Together these results provide a first view into the composition, potential sources, and cycling of this dominant portion of marine DON. Our data indicate that RDON is dominated by 15N-depleted heterocyclic-N structures, entirely distinct from previously characterized HMW material. This fundamentally new view of marine DON composition suggests an important structural control for RDON accumulation and persistence in the ocean. The mechanisms of production, cycling, and removal of these heterocyclic-N-containing compounds now represents a central challenge in our understanding of the ocean's DON reservoir.

Natural sources and controlling factors of urea-nitrogen concentrations in agricultural drainage ditches.

Agricultural drainage ditches accumulate high urea-nitrogen (N) concentrations even in the absence of urea fertilizer applications to adjacent crop fields. The accumulated urea, and other bioavailable forms of dissolved organic nitrogen (DON), can be flushed downstream during substantial rainfall events altering downstream water quality and phytoplankton communities. Sources of urea-N supporting its accumulation in agricultural drainage ditches are poorly understood. A ditch flooding event was simulated using mesocosms with N treatment solutions and monitored for changes in N concentrations, physicochemical properties, dissolved organic matter (DOM) composition, and N cycling enzymes. N concentrations were also monitored in field ditches after two rainfall events. Urea-N concentrations were higher with DON enrichment, but the treatment effects were temporary. The DOM released from the mesocosm sediments was dominated by terrestrial-derived, high molecular weight material. The lack of microbial-derived DOM and evidence from the bacterial gene abundances in the mesocosms suggests that urea-N accumulation after rainfall may not be associated with fresh biological inputs. The urea-N concentrations after spring rainfall and flooding with DON substrates indicated the urea from fertilizers may only temporarily affect urea-N concentrations in drainage ditches. Because urea-N concentrations increased with a high degree of DOM humification, sources of urea may derive from the slow decomposition of complex DOM structures. This study provides further insights of sources contributing to high urea-N concentrations and the types of DOM released from drainage ditches to nearby surface waters after hydrological events.

Source characterization of dissolved organic matter in the eastern Beagle Channel from a spring situation

Dissolved organic matter (DOM) was analyzed by its optical and fluorescent properties in order to study its distribution, source and transformation in relation to microbial abundances, chlorophyll and physicochemical gradients along a transect in the eastern Beagle Channel (BC) during austral spring 2019. Moreover, DOM evolution was followed during three tidal cycles in two fixed stations (F1, F2) separated by the Mackinlay Strait, a hydrographic frontier between water masses under stronger continental influence (inner sector) and that of less modified Sub-Antarctic waters (outer sector). The fluorescence signals of protein- and humic-like compounds were used as a proxy for labile and non-labile material, respectively, while the concentration of nano-, pico- and virioplankton populations, chlorophyll-a (Chl-a) and dissolved organic carbon (DOC) were used as a proxy for biological activity. Moreover, several spectroscopic indices, such as the indicator of microbially produced DOM (BIX), the Freshness index (FIX), an indicator of molecular weight, the Slope Ratio (SR) and an indicator of chromophoric DOM (CDOM), were used to trace the quality and origin of DOM. Chl-a concentration was generally low in the sampling area (< 1 μg L−1) but increased towards the end of the campaign and especially during the visit of F1 along with the concentration of picoeukaryotes and the protein-like fluorophores evidencing the onset of a bloom event. Protein-like fluorophores peaked in the euphotic zone of the inner sector of the BC while humic-like material of terrestrial origin was homogeneously distributed throughout the water column and showed a decreasing gradient towards the outer sector and Atlantic waters. Furthermore, the inner sector was characterized by higher amounts of CDOM, high molecular weight material and more recalcitrant DOM. Accumulation of autochthonous humic-like material in bottom waters of the inner sector along with enhanced values of FIX and BIX preceded by colored organic material suggest an efficient functioning of the microbial carbon pump fueled by terrestrial DOM sources in these waters.

Compound specific δ15N analysis of amino acids reveals unique sources and differential cycling of high and low molecular weight marine dissolved organic nitrogen

Marine dissolved organic nitrogen is the largest pool of reduced nitrogen (N) in the ocean. Yet, despite indications of a bacterial origin, few N-specific approaches have been developed to trace individual microbial N production and degradation mechanisms. Stable nitrogen isotope ratios (δ15N) are one of the most powerful tools to understand sources and cycling of organic N. However, δ15N measurements of total DON can only be made in the surface ocean and interpretations are complicated by the many factors influencing bulk δ15N values. Compound-specific isotope analysis of amino acids (CSI-AA) on isolated DON fractions represents a new approach for DON study throughout the water column with significantly greater information potential. Here, we compare for the first time δ15N amino acid (δ15N-AA) data on baseline inorganic N source and microbial loop processing in coupled ultrafiltered high molecular weight (HMW) and solid-phase extracted low molecular weight (LMW SPE-) DON from the surface to 2500 m deep in the Atlantic and Pacific Subtropical Gyres.δ15N-AA patterns were very different in HMW versus LMW SPE-DON, indicating unique formation and bacterial alteration mechanisms. HMW DON data supported a prior hypothesis that AA in surface HMW DON originate from heterotrophic bacterial production near the nitracline, but also suggests protozoan heterotrophy as an additional major process. In the mesopelagic, distinct HMW DON δ15N-AA patterns suggest heterotrophic bacterial resynthesis of suspended PON. In contrast, the first LMW DON δ15N-AA patterns were surprisingly similar to those of autotrophs, indicating limited resynthesis at any depth. Taken together with prior biomarker data, we hypothesize a direct bacterial surface source of LMW AA-containing molecules which are inherently refractory. Finally, within each size fraction, δ15N-AA patterns were remarkably similar between Station ALOHA and the BATS site, suggesting our findings can be extended to marine DON at least throughout global subtropical gyres.These findings demonstrate CSI-AA as a novel δ15N tool to understand sources and cycling of marine DON at a new level of detail and suggest a significant shift in our understanding of DON source and cycling. Specifically, we hypothesize that the production and degradation mechanisms of LMW AA-containing DON is fundamentally distinct from HMW DON, and that the majority of LMW refractory DON in the sea derives not from degradation of HMW material, but rather from surface production of intrinsically more refractory LMW molecules.

Bioactive Properties of Instant Chicory Melanoidins and Their Relevance as Health Promoting Food Ingredients.

Instant chicory is a caffeine-free brew worldwide consumed as a coffee substitute. Like coffee grounds processing, chicory roots suffer a roasting process, which may lead to the formation of high-molecular weight nitrogen-brown compounds, the melanoidins. It is hypothesized that similarly to coffee, chicory melanoidins have health promoting potential. In this work, the chemical composition and biological activity of chicory high molecular weight material (HMWM) was evaluated. The chicory HMWM is composed by 28.9% (w/w) of carbohydrates, mainly fructose-rich polysaccharides (18.7% w/w) and 5.7% (w/w) of protein, distinct from coffee. The phenolic compounds constituent of the HMWM were mainly present in glycosidically linked and condensed structures (0.9 g/100 g and 5.8 g/100 g), showing in vitro ABTS•+ scavenging (IC50 = 0.28 mg/mL) and ferric ion reducing capacity (ca. 11 µg Fe2+ eq/mg). Chicory HMWM revealed to be effective against Gram-positive bacteria, mainly Staphylococcus aureus and Bacillus cereus, although not so efficient as coffee. It also showed potential to inhibit α-glucosidase activity (15% of inhibition), higher than coffee HMWM, approaching acarbose activity that is used in type 2 diabetes mellitus treatment. Thus, chicory melanoidins, when used as a food ingredient, may contribute to an antioxidant diet and to prevent diabetes, while increasing the protective effects against pathogenic bacteria.

Tuning polycaprolactone degradation for long acting implantables

Polycaprolactone (PCL) is a bioresorbable polyester that has been widely used in biomedical applications since the 1970s. Because PCL undergoes bulk degradation, it is especially amenable to drug delivery applications. To ensure safety, a drug eluting implant must typically remain intact until the drug is exhausted, and following exhaustion the implant should breakdown and be resorbed. Many PCL based implants target delivery on the order of six months to one year, yet the time to degradation of PCLs is often on the order of multiple years. It is known that the time to degradation of PCL is directly related to its initial molecular weight; however, the limited integrity of neat low molecular weight PCLs make them unsuitable for implantation. Here we outline an approach to tune the time to degradation of PCL by blending low and high molecular weight polymers. We show that the degradation rate and permeability of PCL films are insensitive to their composition, and weight-average molecular weight (Mw) is predictive of time to fragmentation. Additionally, we demonstrate that compositions with up to 50 wt % low molecular weight polymer can retain the mechanical properties of a high molecular weight material. The resulting material has a lower effective Mw and a shorter time to degradation. In accelerated testing, it is possible to reduce time to degradation by roughly two-fold without sacrificing mechanical integrity. This provides versatility in adapting device designs to meet the needs of a specific application. These findings have implications in the development of biodegradable drug eluting implants, tissue engineering scaffolds, and resorbable surgical materials.

Process optimization for the valorization of plastic waste into fuel additive production under the zero waste concept

• One of alternative ways to valorize plastic waste under the zero waste concept. • Polycarbonate derived from automobile as a precursor for fuel additive production. • Fuel additive from plastic waste produced by methanolysis under mild condition. • Response surface methodology was usefully assisted for fuel additive production. Synthetic plastic, generally derived from the petrochemical industry, is classified as a high molecular weight material and mostly contains branch and crosslinked polymer structures. However, it cannot be decomposed naturally, which causes a global warming crisis. Therefore, in this research, a fuel additive was prepared from thermoplastic polycarbonate via catalytic methanolysis. Furthermore, statistical response surface methodology (RSM) was applied to obtain process optimization under various reaction times, sodium hydroxide (NaOH) concentrations, and methanol contents. After the reaction, a fuel additive of dimethyl carbonate (DMC) was separated by filtration and distillation. The results revealed that the optimum reaction time (40 min), 0.5 g of NaOH, and 30 g of methanol were obtained. Successfully, a 3.5 g DMC yield, which was equivalent to more than 95% DMC yield, was achieved. The characterization of DMC was also analyzed by Fourier transform infrared spectroscopy. The functional groups of O–H, C–H, C = O and C-O were sequenced in the form of wave frequencies of 3318.46 cm −1 , 2963.33 cm −1 , 1726.84 cm −1 and 1274.04 cm −1 , respectively. Interestingly, the valorization of synthetic plastic waste into fuel additive was achieved under the zero waste concept.

Key odorant melanoidin interactions in aroma staling of coffee beverages

Fractionation of high molecular weight (HMW) coffee melanoidins of varying roasting intensity and evaluation of aroma binding activity via nuclear magnetic resonance spectroscopy revealed two fractions 5–10 kDa and > 50 kDa with high and selective binding affinity toward key coffee odorants. Quantification of monosaccharides, amino acids and phenolic acids, as well as aliphatic organic acids in hydrolysates of HMW material indicated the importance of aromatic residues in the form of hydroxycinnamic acids for the formation of non-covalent interactions with odorants. Caffeic acid concentrations were up to four times higher in fractions 5–10 kDa and > 50 kDa compared to 30–50 kDa and 10–30 kDa fractions. A minimization strategy was developed involving alkaline treatment of the most affine HMW fractions followed by reconstitution at typical coffee concentrations. These reconstituted HMW fractions exhibited up to 25% less aroma binding compared to native fractions of coffee.

Bacterial sources and cycling dynamics of amino acids in high and low molecular weight dissolved organic nitrogen in the ocean

Amino acids (AA) represent the most abundant identifiable biomolecule class in marine dissolved organic nitrogen (DON) and provide powerful proxies for DON degradation state. In particular, the D-enantiomers of AA (D-AA) are known to be derived mainly from bacteria, making them ideal tracers for bacterially derived N. However, despite the widespread use of D-AA tracers, it remains unclear if the accumulation of different D-AA species in the ocean indicates that most DON arises from direct bacterial sources or from continual bacterial alteration of eukaryotic algal material. This difference has major implications for our understanding of sources and cycling mechanisms of DON in the ocean. Here, we present the most extensive D-AA suite ever reported in younger, high molecular weight (HMW) DON contrasted with older, low molecular weight (LMW) solid phase extracted (SPE) DON from the central Atlantic and Pacific Oceans. We evaluate D-AA in these two contrasted MW fractions in the context of multiple common AA-based proxies and bulk DOM radiocarbon (Δ14C) data. Specifically, we assess if D-AA in HMW and LMW SPE-DON are most consistent with 1) preformed bacterial source signals, 2) progressive bacterial degradation/alteration of eukaryotic algal sources, or 3) gradual, continued resynthesis/addition of new bacterial biomolecules during ocean circulation. Our results suggest that AA-containing molecules in HMW and LMW SPE-DON fractions are almost entirely distinct, with independent bacterial sources and degradation mechanisms. In HMW DON, all measured indices support a surface-produced, semi-labile component which is progressively altered in the mesopelagic with increasing radiocarbon age. In contrast, for LMW SPE-DON, AA-based proxies showed conflicting results. Some proxies (D/L ratios of most D-AA, non-protein AA, mol% Gly, and %C-AA) indicated LMW SPE-DON was less labile and more degraded than HMW DON. However other proxies (D/L-Ala, the N isotope based ΣV parameter, and the commonly used DI index) indicated equivalent or even less degradation and resynthesis in the isolated LMW material compared to HMW material, suggesting a disconnect in the underlying mechanisms reflected by different proxies. Finally, AA composition and degradation state in the subsurface samples of both HMW and LMW DON varied little with increasing radiocarbon age, suggesting that HMW and LMW pools may cycle independently. Together, our results suggest that AA DON sources, while almost entirely bacterial, may be more diverse than previously believed, and that much of the hydrolysable AA pool in the ocean may not be derived from proteinaceous material. Overall, these observations support the microbial nitrogen pump idea, but with compositionally unique refractory components in both HMW and LMW material which resist degradation over millennial timescales.

NMR-Based Studies on Odorant-Melanoidin Interactions in Coffee Beverages.

A quantitative 1H NMR-based approach was established, which allowed the direct and noninvasive analysis of molecular interactions between key coffee odorants and high-molecular-weight (HMW) melanoidin polymers. A clear distinction between covalent and noncovalent interactions was achieved by monitoring the time dependency of odorant-polymer interactions, resulting in four scenarios: covalent, π-π, covalent and π-π-, as well as no interactions. Evaluation of temperature influence on e.g. 2-furfurylthiol (FFT), revealed an altered behavior with increased π-π stacking at lower temperatures and accelerated covalent interactions at higher temperatures. Human sensory experiments with HMW material and a coffee aroma reconstitution model showed a drastic reduction of "roasty/sulfury" aroma notes, as well as an increased "sweetish/caramel-like" flavor. The lack of interactions between the "sweetish/caramel" smelling 4-hydroxy-2,5-dimethyl-3(2H)-furanone with the HMW melanoidins in combination with the high binding affinity of coffee thiols explains the sensory evaluation and is obviously the reason for the fast disappearance of the typical "roasty/sulfury" aroma impressions of a freshly prepared coffee brew.

Rethinking Transition Metal Catalyzed N-Carboxyanhydride Polymerization: Polymerization of Pro and AcOPro N-Carboxyanhydrides.

Polyproline (PP) based polypeptides have broad applications as protein mimics, ordered materials, hydrogels, and surface coatings. However, a lack of rapid and efficient preparatory methods has challenged synthesis of well-defined high molecular weight materials. Here, we report facile and high-yielding methods for preparation and polymerization of Pro and trans-4-acetoxy-Pro N-carboxyanhdrides (NCAs). For decades, transition metal initiators of NCA polymerization were assumed to be nonstarters with Pro due to the lack of an amide NH proton. We carefully considered the known steps in the initiation mechanism and applied a Ni initiator that intercepts an intermediate and does not require an NH group. This initiator efficiently catalyzes controlled, living polymerization of Pro NCAs, revealing that routes alternate to the previously proposed mechanism must be at play. We also found Co species can catalyze Pro NCA polymerization, and we improved the synthetic methods to prepare the NCA monomers. Our methods are high-yielding and rapid and give tunable, end-functional PP-based homo, statistical, and block polypeptides. We characterized the conformation of PP and trans-4-hydroxy-PP by CD and confirmed the time scale for quantitative conversion from PPI to PPII helices. Overall, our data shed light on the general propagation mechanism of transition metal catalyzed NCA polymerization and have opened the door for efficient preparation of a desirable class of biomaterials.

Volatile aroma compounds of sugarcane molasses as affected by spray drying at low and high temperature

Sugarcane molasses was chosen as an example material for the investigation of the influence of spray drying approach (conventional high temperature and a developed low temperature drying method which applies dehumidified air as a process gas) and the presence of drying carrier on volatile aroma compounds (VACs). Among 28 identified VACs 10 were chosen for detailed investigation. The influence of drying depended, apart from two mentioned factors, also on the type/origin of VACs and particle morphology. In the case of compounds connected with the fermentation process, the retention was higher after high temperature spray drying. On the contrary, VACs which could be additionally created during spray drying, thus Maillard reaction and caramelization reaction products, were more abundant in samples dried at lower temperature. As was explained, this contradictory phenomenon could be related to the higher evaporative loss at higher temperature, and also the fact that particles created at higher temperature were partially destroyed (as evident from the SEM photos). The presence of carrier increased the content of VACs after low temperature spray drying, which was connected to the encapsulation mechanisms of high molecular weight material. Thus, the most beneficial was the simultaneous application of carrier and low temperature spray drying approach.

Density Functional Theory Investigation of Fulvene-Derivatized Fullerenes as Candidates for Organic Solar Cells.

Interest within the scientific community in organic solar cells has been on the rise over the last two decades as researchers respond to increasing demands for alternative renewable energy sources. Fulvene, fullerene, and endohedral metallofullerene derivatives have individually shown great promise as efficient charge transfer agents. Despite the heavy demand for research in this area, there have been no studies reported to date that explore the electronic behavior of molecules containing both fullerene and fulvene groups. The lack of interest may be attributed to inherent limitations and inaccuracy in most density functional theory (DFT) band gap calculations for large molecules. Herein we present a systematic computational investigation of the band gaps and dipole moments of several test fullerene-fulvene molecules using a novel DFT method that has been modified to allow accurate computation of the band gaps of this class of molecules. Calculated results showed promising low band gap energies and attractive conductive properties for all fullerene-fulvene derivatives. This new DFT method can conceivably be an invaluable tool that can provide predictive insight into the suitability of similar high molecular weight materials for application in organic solar cell devices.

Neutral Nickel(II) Catalysts: From Hyperbranched Oligomers to Nanocrystal-Based Materials

ConspectusPlastics materials are a vital component of modern technologies. They are applied, e.g., in construction, transportation, communication, water supply, or health care. Consequently, polyolefins-the most important plastics by scale-are produced in vast amounts by catalytic polymerization. Effective and selective as the catalysts used may be, their high sensitivity toward any polar compounds limits these methods to hydrocarbon reaction media and monomers like ethylene and propylene, respectively. This can be overcome by less oxophilic late transition metal catalysts, and here particularly neutral nickel(II) catalysts have seen major advances in the past few years. They stand out due to being capable of aqueous catalytic polymerizations. Aqueous polymerizations are benign processes that advantageously yield polymers in the form of particles. Moreover, these catalysts can incorporate polar monomers like acrylates, a realm previously restricted to noble metal catalysts. The introduction of polar moieties can induce properties like compatibility with metals or fibers in high performance composite materials or a desirable degradability.This Account provides a personal account of developments in the past decade. Prior findings are outlined briefly as a background. Aqueous polymerizations afford unique polyethylene morphologies as a result of the unusual underlying particle growth mechanism. Polymer single crystals are formed, which can be composed of a single ultrahigh molecular weight chain. This represents a completely disentangled state of such extremely long polymer chains, which has been long sought-after in order to overcome the difficult processing of high performance ultrahigh molecular weight materials. A key prerequisite for this approach and utilization of these catalysts, in general, is control of polymer branching and molecular weight. This is achieved via remote substituents on the Ni(II)-chelating ligand. Despite their distal position to the active site, weak secondary interactions control whether branching and chain transfer pathways compete very effectively with chain growth or are suppressed entirely. This provides access to hyperbranched oligomers, on the one hand, and enables living polymerizations to strictly linear high molecular weight polymer, on the other hand. Other advanced catalysts provide linear copolymers with in-chain polar monomer repeat units for the first time with non-noble metal active sites. Mechanistic studies further revealed that for copolymerizations with polar vinyl monomers the decisive limiting factor is irreversible termination reactions with neutral Ni(II) catalysts, rather than the well-recognized reversible blocking of coordination sites by the polar functional groups found for other types of catalysts. The mechanistic picture also implies the possibility of free-radical pathways, and their role in the formation of desirable polymer end groups and polymer blends is now being recognized. The area of neutral Ni(II) catalysts has progressed significantly in the entire range from fundamental mechanistic understanding, catalyst performance, and previously inaccessible polymer microstructures, and it is moving forward to materials through unique concepts. The unprecedented ability to incorporate functional groups into linear crystalline polyethylene also provides perspectives for much needed polyolefin materials that will not persist in the natural environment for several decades but that can be degraded by virtue of low levels of functional groups.

Molecular and emulsifying properties of arachin and conarachin of peanut protein isolate from ultrasound-assisted extraction

The present study aimed to investigate the particle size, molecular weight distribution, secondary structure, and nanostructures of arachin and conarachin of peanut protein isolates produced using ultrasound-assisted extraction, as well as the characteristics of their emulsions. The results indicated that ultrasound-assisted extraction could improve the emulsifying properties of arachin and conarachin. Arachin obtained via ultrasound-assisted extraction had smaller particle size, lower content of high molecular weight material, a higher percentage of α-helix structure, and a higher number of exposed hydrophobic groups compared with those obtained using the regular alkali soluble and acid precipitation method. However, no obvious changes in the secondary structure of conarachin after ultrasound-assisted extraction were observed. The least amount of droplet flocculation and smallest values of the averaged particle size of emulsions stabilized by arachin and conarachin were obtained using an ultrasound time of 30 min, which also produced the highest absolute values of zeta potential. Ultrasound-assisted extraction changed the composition and structure of arachin, which led to a marked improvement in the emulsifying properties. Ultrasound-assisted extraction has a great application potential in the plant protein industry.

Cell surface changes that advance the application of using yeast as a food emulsifier

A previous study revealed that Saccharomyces cerevisiae mcd4Δ, a cell wall mutant with a defect in the synthesis of the glycosylphosphatidylinositol anchor, has a strong macrophage activation ability. In this study, remarkable emulsion formation after cell suspensions of mcd4Δ and anp1Δ (which exhibit an extreme reduction of mannan) were mixed with oil was found. Moreover, the relationship between cell wall mutation and emulsion formation was investigated, suggesting that och1Δ with a defect in the formation of N-linked glycans also had a strong emulsification ability and that high molecular weight materials released from the cells were involved in emulsion formation. Furthermore, two strains (asc1Δ and scp160Δ) with a strong emulsification ability without a large decrease in mannan content were also found from the wide screening of strains that exhibit an emulsifying activity using more than 5000 gene-deficient strains. These results provide valuable information for the development of a yeast-derived emulsifier.

Influence of the physico-chemical properties of root mucilage and model substances on the microstructural stability of sand

Root mucilage (RM), a soil-born biohydrogel, affects the physical stability of the rhizosphere. One reason for this is attributed to the present polysaccharides which contribute to the formation of aggregates by acting as interparticulate glue. The aim of this study was to explore how physico-chemical properties of polymers of interparticulate gels influence this gluing and thus soil microstructural stability. We hypothesized that the microstructural stability of sand increases with the viscosity of the amended biohydrogel, which depends on the content of carbohydrate polymers and non-esterified uronic acids which themselves determine the amount of absorbed calcium. Therefore, natural RM of maize and wheat were compared with higher viscous chia seed mucilage (SM) as a widely used model for RM, and with industrial pectin rich in uronic acids partially methylated. Results show that additionally to Ca binding by uronic acids, binding by proteins is a further possible mechanism of Ca adsorption in RM. Upon Ca addition, the viscosity increased upon intermolecular associations (pectin) and decreased upon suppression of intermolecular charge–charge repulsion (chia SM, maize RM). Amount of high-molecular weight material in the amendment affected strongly soil microstructural stability. Results further suggest the creation of gel micro-zones upon Ca addition, which increase the viscosity of interparticulate gel and sand microstructural stability. Finally, the study outlines several physico-chemical mechanisms through which interactions between biotic (roots and seed) and abiotic components (mineral particles) influence soil structure, which control the water, air and nutrient flow through the rhizosphere and is, thus, an important soil quality parameter.

Thermal, Mechanical and Rheological Properties of Poly(lactic acid) Chain Extended with Polyaryl Polymethylene Isocyanate

In this study, polyaryl polymethylene isocyanate (PAPI) was used as a chain extender for poly(lactic acid) (PLA) to produce a high molecular weight material with better rheological, thermal and mechanical properties. The reaction between PLA chains and PAPI was proved by FTIR during reactive blending. The results showed that the molecular weight and molecular weight distribution were increased with the addition of PAPI content due to the chain extension. Chain extension was also responsible for the increased modulus and complex viscosity. The glass transition temperature (Tg) and thermal stability increased by incorporating with PAPI. The results of mechanical properties showed that a considerably higher tensile strength and Young’s modulus of the reactive blends compared with neat PLA.