Cell Wall Porosity Research Articles

Desiccation tolerance in bryophytes relates to elasticity but is independent of cell wall thickness and photosynthesis.

Mosses have been found outliers of the trade‐off between photosynthesis and bulk elastic modulus described for vascular plants. Hence, potential trade‐offs among physical features of cell walls and desiccation tolerance, water relations, and photosynthesis were assessed in bryophytes and other poikilohydric species. Long‐term desiccation tolerance was quantified after variable periods of desiccation/rehydration cycles. Water relations were analyzed by pressure–volume curves. Mesophyll conductance was estimated using both CO2 curve‐fitting and anatomical methods. Cell wall elasticity was the parameter that better correlated with the desiccation tolerance index for desiccation tolerant species and was antagonistic to higher absolute values of osmotic potential. Although high values of cell wall effective porosity were estimated compared with the values assumed for vascular plants, the desiccation tolerance index negatively correlated with the porosity in desiccation tolerant bryophytes. Neither cell wall thickness nor photosynthetic capacity were correlated with the desiccation tolerance index of the studied species. The existence of a potential evolutionary trade‐off between cell wall thickness and desiccation tolerance is rejected. The photosynthetic capacity reported for bryophytes is independent of elasticity and desiccation tolerance. Furthermore, the role of cell wall thickness in limiting CO2 conductance would be overestimated under a scenario of high cell wall porosity for most bryophytes.

A Comparative Investigation on Structural and Chemical Differences between the Pith and Rind of Sunflower Stalk and Their Influences on Nanofibrillation Efficiency

The structure and chemical composition of cell walls play a vital role in the bioconversion and utilization of plants. In the present study, the cell wall structure and chemical composition of pith and rind from sunflower stalks were compared and correlated to their nanofibrillation efficiency with ultrasonic treatment. Mild chemical pretreatment using 1% or 4% NaOH without any bleaching process were applied prior to ultrasonication nanofibrillation. Significant structural and chemical differences were demonstrated between the pith and rind, with the former exhibiting a much lower lignin and hemicellulose contents, higher pectin, much looser cell structure and higher cell wall porosity than the latter. Alkaline treatment alone was sufficient to eliminate most of the hemicellulose and pectin from stalk pith, whereas only partial removal of hemicellulose and lignin was achieved for the woody rind part. After 30 min of ultrasonic treatment, the stalk pith exhibited fully defibrillated fibrils with a continuous and entangled micro/nanofibrillated network, whereas numerous micron-sized fiber and fragments remained for the rind. The results indicated that stalk pith is less recalcitrant and easier to be fibrillated with ultrasonication than rind, which must be correlated to their distinct differences in both structure and chemical composition.

Molecular sensors reveal the mechano-chemical response of Phytophthora infestans walls and membranes to mechanical and chemical stress

Phytophthora infestans, causal agent of late blight in potato and tomato, remains challenging to control. Unravelling its biomechanics of host invasion, and its response to mechanical and chemical stress, could provide new handles to combat this devastating pathogen. Here we introduce two fluorescent molecular sensors, CWP-BDP and NR12S, that reveal the micromechanical response of the cell wall-plasma membrane continuum in P. infestans during invasive growth and upon chemical treatment. When visualized by live-cell imaging, CWP-BDP reports changes in cell wall (CW) porosity while NR12S reports variations in chemical polarity and lipid order in the plasma membrane (PM). During invasive growth, mechanical interactions between the pathogen and a surface reveal clear and localized changes in the structure of the CW. Moreover, the molecular sensors can reveal the effect of chemical treatment to CW and/or PM, thereby revealing the site-of-action of crop protection agents. This mechano-chemical imaging strategy resolves, non-invasively and with high spatio-temporal resolution, how the CW-PM continuum adapts and responds to abiotic stress, and provides information on the dynamics and location of cellular stress responses for which, to date, no other methods are available.

Cell wall thickness and composition are related to photosynthesis in Antarctic mosses.

Cell wall thickness (Tcw ) has been proposed as an important anatomical trait that could determine photosynthesis through land plants' phylogeny, bryophytes being the plant group presenting the thickest walls and the lowest photosynthetic rates. Also, it has recently been suggested that cell wall composition may have the potential to influence both thickness and mesophyll conductance (gm ), representing a novel trait that could ultimately affect photosynthesis. However, only a few studies in spermatophytes have demonstrated this issue. In order to explore the role of cell wall composition in determining both Tcw and gm in mosses, we tested six species grown under field conditions in Antarctica. We performed gas exchange and chlorophyll fluorescence measurements, an anatomical characterization, and a quantitative analysis of cell wall main composition (i.e., cellulose, hemicelluloses and pectins) in these six species. We found the photosynthetic rates to vary between the species, and they also presented differences in anatomical characteristics and in cell wall composition. Whilst gm correlated negatively with Tcw and pectins content, a positive relationship between Tcw and pectins emerged, suggesting that pectins could contribute to determine cell wall porosity. Although our results do not allow us to provide conclusive statements, we suggest for the first time that cell wall composition-with pectins playing a key role-could strongly influence Tcw and gm in Antarctic mosses, ultimately defining photosynthesis.

Yeast as a novel protein source - Effect of species and autolysis on protein and amino acid digestibility in Atlantic salmon (Salmo salar)

Yeasts are gaining increasing attention as alternative protein sources in fish feeds. The nutritional value of yeast depends on cultivation conditions, yeast species and processing conditions used after harvesting. The objective of the current study was to evaluate the effect of autolysis on apparent digestibility coefficients (ADCs) of crude protein and amino acids (AA) of different yeasts species in Atlantic salmon (Salmo salar). Three yeast species (i.e. Cyberlindnera jadinii, Blastobotrys adeninivorans and Wickerhamomyces anomalus) produced from hydrolysates of pre-treated wood and chicken products were used. After harvesting, each yeast was either directly heat-inactivated with spray-drying or autolyzed at 50 °C for 16 h followed by spray-drying. The treatments consisted of a high-quality fishmeal-based reference diet and six test diets containing 30% of each of the yeast product and 70% of the reference diet. The results showed that protein and AA digestibility differed among the yeast species and that the effect of autolysis on nutrient digestibility was inconsistent among the three yeast species. The ADCs of protein in inactivated yeasts were 63%, 72%, 66% in C. jadinii, B. adeninivorans and W. anomalus, respectively. Autolysis increased the ADCs of protein by 12% and 9% in C. jadinii and W. anomalus, respectively, while it remained unchanged for B. adeninivorans. The ADCs of lysine were 67%, 79% and 72% in inactivated C. jadinii, B. adeninivorans and W. anomalus, respectively. Autolysis improved the ADCs of lysine by 15%, 7% and 13% in C. jadinii, B. adeninivorans and W. anomalus, respectively. The ADCs of methionine in inactivated yeasts was 47% in C. jadinii, 81% in B. adeninivorans and 74% in W. anomalus. After autolysing the yeasts, the ADC of methionine improved by 26% and 4% in C. jadinii and B. adeninivorans, respectively, while it slightly reduced by 2% in W. anomalus. Data from regression analyses showed that digesta viscosity, digesta dry matter and nitrogen solubility are important determinants of protein digestibility of yeasts in fish. In addition, cell wall porosity as demonstrated by nitrogen solubility test, had a larger impact on nutrient digestibility of yeasts compared to the cell wall thickness. In conclusion, the digestibility of protein and AA of yeasts in Atlantic salmon depends on type of yeasts and down-stream processing applied after harvesting. Also, the particular in vitro digestibility method used in the current study did not adequately reflect the protein digestibility of yeasts in Atlantic salmon.

Effects of extraction process on the dried cell wall pore structure of messmate heartwood

In order to study the effects of a messmate heartwood extraction process on its cell wall pore structure and its drying ability, its nanopore structure was explored after via gas adsorption technology. Specifically, the messmate heartwood particles were extracted with methanol, and then the cell wall pore structure of the original and extracted samples were evaluated by N2 and CO2 sorption and pycnometer methods, respectively. Overall, compared with the original samples, the cell wall porosity, micropore volume, mesopore volume, BET specific surface area, and specific surface area of the micropores of the extracted messmate heartwoods increased by 2.55%, 0.007 cm3/g, 0.0014 cm3/g, 0.24 m2·g-1, and 21.9 m2·g-1, respectively. The cell wall pore volume measured via the gas adsorption method was smaller than the measurement from the pycnometer method. The results indicated that the presence of extractives made the messmate cell wall have a decreased pore volume and porosity, which may be one of the reasons messmate wood is difficult to dry. Messmate extractives primarily were present in the micropores of the cell wall in the range of 0.4 nm to 0.7 nm. However, gas sorption technology could not detect all the pores in the cell wall of the messmate heartwood sample.

Cell wall polymers in the Phaeoceros placenta reflect developmental and functional differences across generations.

The placenta of hornworts is unique among bryophytes in the restriction of transfer cells that are characterized by elaborate wall labyrinths to the gametophyte generation. During development, cells around the periphery of the sporophyte foot elongate, forming smooth-walled haustorial cells that interdigitate with gametophyte cells. Using immunogold labeling with 22 antibodies to diverse cell wall polymers, we examined compositional differences in the developmentally and morphologically distinct cell walls of gametophyte transfer cells and sporophyte haustorial cells in the placenta of Phaeoceros. As detected by Calcofluor White fluorescence, cellulose forms the cell wall scaffolding in cells on both sides of the placenta. Homogalacturonan (HG) and rhamnogalacturonan I (RG-I) pectins are abundant in both cell types, and haustrorial cells are further enriched in methyl-esterified HGs. The abundance of pectins in placental cell walls is consistent with the postulated roles of these polymers in cell wall porosity and in maintaining an acidic apoplastic pH favorable to solute transport. Xyloglucan hemicellulose, but not mannans or glucuronoxylans, are present in cell walls at the interface between the two generations with a lower density in gametophytic wall ingrowths. Arabinogalactan proteins (AGPs) are diverse along the plasmalemma of placental cells and are absent in surrounding cells in both generations. AGPs in placental cell walls may play a role in calcium binding and release associated with signal transduction as has been speculated for these glycoproteins in other plants. Callose is restricted to thin areas in cell walls of gametophyte transfer cells. In contrast to studies of transfer cells in other systems, no reaction to the JIM12 antibody against extensin was observed in Phaeoceros.

A synthetic 5,3-cross-link in the cell wall of rod-shaped Gram-positive bacteria

Gram-positive bacteria assemble a multilayered cell wall that provides tensile strength to the cell. The cell wall is composed of glycan strands cross-linked by nonribosomally synthesized peptide stems. Herein, we modify the peptide stems of the Gram-positive bacterium Bacillus subtilis with noncanonical electrophilic d-amino acids, which when in proximity to adjacent stem peptides form novel covalent 5,3-cross-links. Approximately 20% of canonical cell-wall cross-links can be replaced with synthetic cross-links. While a low level of synthetic cross-link formation does not affect B. subtilis growth and phenotype, at higher levels cell growth is perturbed and bacteria elongate. A comparison of the accumulation of synthetic cross-links over time in Gram-negative and Gram-positive bacteria highlights key differences between them. The ability to perturb cell-wall architecture with synthetic building blocks provides a novel approach to studying the adaptability, elasticity, and porosity of bacterial cell walls.

Impact of Meloidogyne incognita (nematode) infection on root tissues and cell wall composition of okra (Abelmoschus esculentus L. Moench, Malvaceae).

Root-knot nematodes are endoparasites whose mature females lodge and grow inside the root of some cultivated plants, leading to losses in productivity. Herein, we investigated if the infection of okra, Abelmoschus esculentus (Malvaceae), promoted by the root-knot nematode Meloidogyne incognita (Meloidogynidae) changes some agronomic traits of the host plant, as well as the cell wall composition of the root tissues. The okra Santa Cruz 47® cultivar was infected with a suspension of 5000 M. incognita juveniles. The inoculated and non-inoculated okra plants were then submitted to morphological analysis at the end of experiment, as well as histological (at 4, 11, 18, 39, ad 66 days after inoculation) and immunocytochemical analysis (control and 66 days after inoculation). Root-knot nematode infection reduced the dry weight of the stem system but, unexpectedly, the number and weight of fruits increased. At 11 days after inoculation, we detected the presence of giant cells that increased in number and size until the end of the experiment, at 66 days after inoculation. These cells came from the xylem parenchyma and showed intense and moderate labeling for epitopes recognized by JIM5 and JIM7. The presence of homogalacturonans (HGs) with different degrees of methyl esterification seems to be related to the injuries caused by the nematode feeding activity and to the processes of giant cell hypertrophy. In addition, the presence of HGs with high methyl-esterified groups can increase the cell wall porosity and facilitate the flux of nutrients for the root-knot nematode.

In vitro fermentation of legume cells and components: Effects of cell encapsulation and starch/protein interactions

Intact legume cotyledon cell walls (CW) hinder the access of digestive enzymes and maintain the physical integrity of cellular structures under in vitro and in vivo conditions, resulting in the transport of cellular structures and their contents from food legumes to the large intestine. The subsequent colonic fermentation of intact legume cells and polymer components is not well understood. In vitro fermentation of intact cells, broken cells, isolated starch, and cell walls from low (60 °C; LHT) and high (95 °C; HHT) heat-treated pea, and mungbean was carried out for 72 h after inoculation with mixed faeces from five pigs fed a controlled (legume-free) diet. The rate and extent of cumulative gas production, short chain fatty acid end-products, as well as alpha-amylase and protease activities, were found to be dependent on cellular integrity, botanical origin, and thermal treatment. For isolated CW and starch substrates, similar fermentation behaviour was found across the three legume types, including a decrease in starch molecular order during the fermentation process. However three different fermentation extents were observed for intact and broken cells: intact > broken for mungbean, intact ~ broken for HHT pea, and intact < broken for LHT pea. These differences can be rationalised on the basis of substrate differences in cell wall porosity and starch/protein interactions. The fermentability of processed legumes containing intact or broken cells therefore cannot be predicted from a knowledge of the fermentation behaviour of constituent starch and cell wall components and depends on both botanical origin and processing history.

Reduced pectin content of cell walls prevents stress-induced root cell elongation in Arabidopsis.

The primary cell walls of plants provide mechanical strength while maintaining the flexibility needed for cell extension growth. Cell extension involves loosening the bonds between cellulose microfibrils, hemicelluloses and pectins. Pectins have been implicated in this process, but it remains unclear if this depends on the abundance of certain pectins, their modifications, and/or structure. Here, cell wall-related mutants of the model plant Arabidopsis were characterized by biochemical and immunohistochemical methods and Fourier-transform infrared microspectroscopy. Mutants with reduced pectin or hemicellulose content showed no root cell elongation in response to simulated drought stress, in contrast to wild-type plants or mutants with reduced cellulose content. While no association was found between the degrees of pectin methylesterification and cell elongation, cell wall composition analysis suggested an important role of the pectin rhamnogalacturonan II (RGII), which was corroborated in experiments with the RGII-modifying chemical 2β-deoxy-Kdo. The results were complemented by expression analysis of cell wall synthesis genes and microscopic analysis of cell wall porosity. It is concluded that a certain amount of pectin is necessary for stress-induced root cell elongation, and hypotheses regarding the mechanistic basis of this result are formulated.

Mesophyll conductance: walls, membranes and spatial complexity.

A significant resistance to CO2 diffusion is imposed by mesophyll tissue inside leaves. Mesophyll resistance, rm (or its reciprocal, mesophyll conductance, gm ), reduces the rate at which Rubisco can fix CO2 , increasing the water and nitrogen costs of carbon acquisition. gm varies in proportion to the surface area of chloroplasts exposed to intercellular airspace per unit leaf area. It also depends on the thickness and effective porosity of the cell wall and the CO2 permeabilities of membranes. As no measurements exist for the effective porosity of mesophyll cell walls, and CO2 permeability values are too low to account for observed rates of CO2 assimilation, conclusions from modelling must be treated with caution. There is great variation in the mesophyll resistance per unit chloroplast area for a given cell wall thickness, which may reflect differences in effective porosity. While apparent gm can vary with CO2 and irradiance, the underlying conductance at the cellular level may remain unchanged. Dynamic changes in apparent gm arise for spatial reasons and because chloroplasts differ in their photosynthetic composition and operate in different light environments. Measurements of the temperature sensitivity of membrane CO2 permeability are urgently needed to explain variation in temperature responses of gm .

Determination of mesopores in the wood cell wall at dry and wet state

Wood porosity is of great interest for basic research and applications. One aspect is the cell wall porosity at total dry state. When water is absorbed by wood, the uptake of water within the cell wall leads to a dimension change of the material. A hypothesis for possible structures that hold the water is induced cell wall porosity. Nitrogen and krypton physisorption as well as high pressure hydrogen sorption and thermoporosimetry were applied to softwood and hardwood (pine and beech) in dry and wet state for determining surface area and porosity. Physisorption is not able to detect pores or surface area within the cell wall. Krypton physisorption shows surface area up 5 times lower than nitrogen with higher accuracy. With high pressure sorption no inaccessible pore volumes were seen at higher pressures. Thermoporosimetry was not able to detect mesopores within the hygroscopic water sorption region. Physisorption has to be handled carefully regarding the differences between adsorptives. The absence of water-induced mesopores within the hygroscopic region raise doubts on existing water sorption theories that assume these pore dimensions. When using the term “cell wall porosity”, it is important to distinguish between pores on the cell wall surface and pores that exist because of biological structure, as there are no water-induced mesopores present. The finding offers the possibility to renew wood-water-sorption theories because based on the presented results transport of water in the cell wall must be realized by structures lower than two 2 nm. Nanoporous structures in wood at wet state should be investigated more intensively in future.

Immunocytochemistry and Density Functional Theory evidence the competition of aluminum and calcium for pectin binding in Urochloa decumbens roots

Root growth is reduced in soils with low pH [H+] and abundant soluble aluminum [Al3+], which can be a consequence of the interaction between Al3+ and cell wall composition. The competition between Al3+ and Ca2+ toward binding to pectin molecules was evaluated in roots of Urochloa decumbens, an African grass highly adapted to acidic Al-rich soils. Variations in the composition and distribution of pectins can change the extensibility, rigidity, porosity, and adhesive properties of plant cell walls, which were tested in seedlings of U. decumbens exposed to pH 3.5, 4.5 and 5.8 and to 0, 80, 160 and 320 μM of Al3+ for 80h. Root growth corroborated that U. decumbens is very tolerant to soil acidity, with effective reduction of root growth only at pH 3.5. Immunocytochemical approaches demonstrated variations in pectin composition induced both by Al3+ and by H+ in root tissues and zones. Based on the usual linkage between Ca2+ and pectins, Density Functional Theory (DFT) analyses indicated that Al3+ bound easier to pectins than Ca2+ did, leading to the formation of more Al3+-pectate complexes than Ca2+-pectate complexes, which resulted in higher rigidity of cell walls, and hampered cell extension.

Production and Mechanical Characterisation of TEMPO-Oxidised Cellulose Nanofibrils/β-Cyclodextrin Films and Cryogels.

Wood-based TEMPO-oxidised cellulose nanofibrils (toCNF) are promising materials for biomedical applications. Cyclodextrins have ability to form inclusion complexes with hydrophobic molecules and are considered as a method to bring new functionalities to these materials. Water sorption and mechanical properties are also key properties for biomedical applications such as drug delivery and tissue engineering. In this work, we report the modification with β-cyclodextrin (βCD) of toCNF samples with different carboxyl contents viz. 756 ± 4 µmol/g and 1048 ± 32 µmol/g. The modification was carried out at neutral and acidic pH (2.5) to study the effect of dissociation of the carboxylic acid group. Films processed by casting/evaporation at 40 °C and cryogels processed by freeze-drying were prepared from βCD modified toCNF suspensions and compared with reference samples of unmodified toCNF. The impact of modification on water sorption and mechanical properties was assessed. It was shown that the water sorption behaviour for films is driven by adsorption, with a clear impact of the chemical makeup of the fibres (charge content, pH, and adsorption of cyclodextrin). Modified toCNF cryogels (acidic pH and addition of cyclodextrins) displayed lower mechanical properties linked to the modification of the cell wall porosity structure. Esterification between βCD and toCNF under acidic conditions was performed by freeze-drying, and such cryogels exhibited a lower decrease in mechanical properties in the swollen state. These results are promising for the development of scaffold and films with controlled mechanical properties and added value due to the ability of cyclodextrin to form an inclusion complex with active principle ingredient (API) or growth factor (GF) for biomedical applications.

Top-Down Approach Making Anisotropic Cellulose Aerogels as Universal Substrates for Multifunctionalization.

Highly porous, strong aerogels with anisotropic structural properties are of great interest for multifunctional materials for applications including insulators in buildings, filters for oil cleanup, electrical storage devices, etc. Contemporary aerogels are mostly extracted from fossil resources and synthesized from bottom-up techniques, often requiring additional strategies to obtain high anisotropy. In this work, a universal approach to prepare porous, strong, anisotropic aerogels is presented through exploiting the natural hierarchical and anisotropic structure of wood. The preparation comprises nanoscale removal of lignin, followed by dissolution–regeneration of nanofibers, leading to enhanced cell wall porosity with nanofibrillated networks occupying the pore space in the cellular wood structure. The aerogels retain structural anisotropy of natural wood, exhibit specific surface areas up to 247 m2/g, and show high compression strength at 95% porosity. This is a record specific area value for wood aerogels/foams and even higher than most cellulose-based aerogels for its assigned strength. The aerogel can serve as a platform for multifunctional composites including scaffolds for catalysis, gas separation, or liquid purification due to its porous matrix or as binder-free electrodes in electronics. To demonstrate the multifunctionality, the aerogels are successfully decorated with metal nanoparticles (Ag) and metal oxide nanoparticles (TiO2) by in situ synthesis, coated by the conductive polymer (PEDOT:PSS), and carbonized to yield conductive aerogels. This approach is found to be a universal way to prepare highly porous anisotropic aerogels.

MsPG1 alleviated aluminum-induced inhibition of root growth by decreasing aluminum accumulation and increasing porosity and extensibility of cell walls in alfalfa (Medicago sativa)

Pectins are abundant in the primary cell walls and involve in regulating intercellular adhesion. MsPG1gene was cloned from alfalfa and its function of Al tolerance was tested in vivo and vitro. Results showed that the expression of MsPG1 was increased by Al, and the MsPG1 was localized in the plasma membrane of epidermal cells in root apexes. Overexpression of MsPG1 in hairy roots of alfalfa increased root growth in the present of Al, which was attributed to the decreased Al accumulations in pectins, hemicellulose 1 (HC1), cell walls and root apexes conferred by the decreased content of HC1 and ratios of negatively charged functional groups (−OH and −COOH) in cell wall. The decreased Al accumulations in pectins and cell walls were also observed in incubation MsPG1 with pectins and cell walls in vitro. TEM and FESEM assays showed that overexpression of MsPG1 protected the cell microstructure of root apexes, and increased the porosity and pore size of porous lattice-like structure of cell wall in the present of Al. These results indicated that MsPG1 could increase Al tolerance of alfalfa via decreasing Al accumulation in cell wall and increasing the porosity and extensibility of cell wall under excess Al stress.

Relationship Between Porosity and Spacer Content of Open Cell Metal Foams

Metal foams with high melting points are generally fabricated by the space holder technique. Foams with desirable pore size, shape and distribution can be obtained by using appropriate space holder. However, porosity (P) is always not equal to spacer content (ϕmac), which makes it difficult to obtain the expected porosity. In this study, a model equation for describing the relationship between P and ϕmac was established based on theory, i.e., P = (a1ϕmac + a2)/(a3ϕmac + a4). Each coefficient ai (i.e., a1, a2, a3, a4) could be determined by the porosity of cell walls (Pcell wall) and the volume change rate of macropores (Rmac). The theoretical equation was in accordance with the experimental results by authors and in the studies. It implies that Pcell wall and Rmac can be considered as constants in one certain production condition.

The effects of cell density and intrinsic porosity on structural properties and adsorption kinetics in 3D-printed zeolite monoliths

Herein, we report the evaluation of dynamic performance of 3D-printed zeolite monoliths for CO2/N2 separation at 5 bar 25 °C. Monoliths with various cell densities (200, 400, 600 cpsi) and porosities (0.23–0.46) were printed and the effects of cell density, wall porosity, and inlet gas velocity on their separation performance were investigated. Dynamic breakthrough tests with 10% CO2/N2 revealed that increasing cell density gives rise to gas throttling, inadequate time for molecular mass transfer, and broad wavefronts. For 200 cpsi monoliths, upon increasing wall porosity from 0.23 to 0.46, the mass transfer zone (MTZ) length decreased from 0.40 cm to 0.07 cm at the feed velocity of 1.8 cm/s. The mass transfer coefficients estimated from modeling the breakthrough profiles were found to decrease steadily with both velocity and monolith cell density. In the macroporous samples, the best mass transfer coefficient was found to be 0.049 s−1 for the 200 cpsi monolith with kaolin binder substitution. Both increasing the plasticizer concentration and substituting a macroporous binder promoted mass transfer rate, however, the former method increased the number of zeolite-bentonite bonds around large surface defects during burnout and reduced the CO2 adsorption capacity by 27% from the other formulations. On the basis of adsorption capacity and kinetics, utilization of a macroporous binder was found to be the best method of developing 3D-printed zeolite monoliths because it could reduce intraparticle resistance without compromising adsorption capacity or mechanical integrity.

Effect of soybean processing on cell wall porosity and protein digestibility.

Apart from the presence of antinutritional factors, digestibility of soybean proteins is limited in intact cells by cell wall permeability to proteolitic enzymes. Food processing may modulate cell wall permeability and hence the accessibility of protease enzymes to intracellular proteins. In this study, soybeans were processed in various ways, e.g. cooking applied alone or with either germination or fermentation processes, and the modification in cell wall permeability was investigated using confocal microscopy to visualize the penetration of FITC-dextran probes into isolated cells/cell clusters. Diffusion of fluorescently labelled trypsin into cells and cell clusters was also monitored. Microscopy observations showed that fermentation and germination as well as proteolitic enzymes increase the permeability of boiled soybean cotyledon cells. The diffusion of trypsin into all the isolated cells was observed at an early stage of simulated in vitro digestion, whereas diffusion into cell clusters was delayed due to a bigger size and limited permeability of cell clusters. A modest, although significant, increase in protein digestibility was observed when boiling was combined with fermentation or germination likely due to pre-digestion of storage proteins and inactivation of trypsin inhibitors. This study highlights the positive role of fermentation and germination in improving protein digestibility in soybeans but overall suggests that cell wall permeability to trypsin plays a minor role in the extent of protein digestion of intact soybean cells.