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Background The effectiveness of the enzymatic hydrolysis of cellulose in plant cell wall is strongly influenced by the access of enzymes to cellulose, which is at least in part limited by the presence of lignin. Although physicochemical treatments preceding the enzymatic catalysis significantly overcome this recalcitrance, the residual lignin can still play a role in the process. Lignin is suggested to act as a barrier, hindering cellulose and limiting the access of the enzymes. It can also unspecifically bind cellulases, reducing the amount of enzymes available to act on cellulose. However, the limiting role of the lignin present in pretreated sugarcane bagasses has not been fully understood yet. Results A set of sugarcane bagasses pretreated by five leading pretreatment technologies was created and used to assess their accessibility and the unproductive binding capacity of the resulting lignins. Steam explosion and alkaline sulfite pretreatments resulted in more accessible substrates, with approximately 90% of the cellulose hydrolyzed using high enzyme loadings. Enzymatic hydrolysis of alkaline-treated (NaOH) and steam-exploded sugarcane bagasses were strongly affected by unproductive binding at the lowest enzyme loading tested. Analysis of the extracted lignins confirmed the superior binding capacity of these lignins. Sulfite-based pretreatments (alkaline sulfite and acid sulfite) resulted in lignins with lower binding capacities compared to the analogue pretreatments without sulfite (alkaline and acidic). Strong acid groups present in sulfite-based pretreated substrates, attributed to sulfonated lignins, corroborated the lower binding capacities of the lignin present in these substrates. A more advanced enzyme preparation (Cellic CTec3) was shown to be less affected by unproductive binding at low enzyme loading. Conclusions Pretreatments that increase the accessibility and modify the lignin are necessary in order to decrease the protein binding capacity. The search for the called weak lignin-binding enzymes is of major importance if hydrolysis with low enzyme loadings is the goal for economically viable processes.

In this study, a calcium-binding peptide was obtained by hydrolyzing tilapia bone and its osteogenic activity was evaluated. Animal protease was selected from nine enzymes, and its hydrolysate was purified through preparative and semi-preparative reverse phase high-performance liquid chromatography. The purified peptide was identified as DGPSGPK (656.32 Da) and its calcium-binding capacity reached 111.98 µg/mg. The peptide calcium chelate (DGPSGPK-Ca) was obtained, and its structure was characterized through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and mass spectrometry (MS). The results of XRD and SEM showed that DGPSGPK-Ca was formed as a new compound. The carboxyl and amino groups of Lys and Asp residues may be the chelating sites of DGPSGPK according to the FTIR and MS results. The molecular simulation showed the carbonyl groups of Asp, Pro, Ser, and Lys residues involved in the binding of calcium. The interaction of DGPSGPK and different integrins was evaluated by molecular docking simulation, and the main forces involved were electrostatic interaction forces, hydrogen bonding and hydrophobic interactions. Furthermore, DGPSGPK could inhibit the differentiation of osteoclast and promote the proliferation, differentiation and mineralization of osteoblasts.

Polymer-grafted chromatography media, especially ion exchangers, are high performance materials for protein purification. However, due to the pore size limitation, conventional chromatography beads are usually not considered for the downstream processing of large biomolecules such as virus-like particles (VLPs). Contrariwise, since the outer surface of the chromatography beads provides satisfactory binding capacity for VLPs and impurities of smaller size can bind inside of the beads, conventional porous beads should be considered for VLP capture and purification. We used HIV-1 gag VLPs with a diameter of 100–200 nm as a model to demonstrate that polymer-grafted anion exchangers are suitable for the purification of bionanoparticles. The equilibrium binding capacity was 1 × 1013 part/mL resin. Moderate salt concentration up to 100 mM NaCl did not affect binding, allowing direct loading of cell culture supernatant onto the column for purification. Dynamic binding capacity at 10% breakthrough, when loading cell culture supernatant, was approximately 6 × 1011 part/mL column; only 1-log lower than for monoliths. Endonuclease treatment of the cell culture supernatant did not increase the dynamic binding capacity, suggesting that dsDNA does not compete for the binding sites of VLPs. Nevertheless, due to simultaneous elution of particles and dsDNA, endonuclease treatment is required to reduce dsDNA contamination in the product. Proteomic analysis revealed that HIV-1 gag VLPs contain different host cell proteins in their cargo. This cargo is composed of conserved proteins and other proteins that vary from one particle population to another, as well as from batch to batch. This process allowed the separation of different particle populations. HIV-1 gag VLPs were directly captured and purified from cell culture supernatant with a total particle recovery in the elution of about 35%. Columns packed with beads can be scaled to practically any dimension and therefore a tailored design of the process is possible.

This study investigated the in vitro digestibility, glycaemic index (GI) and bile acid–binding capacity (BABC) of some potential resistant starch source food products (PRSF). Commercially available resistant starch (RS) samples, Hylon VII (RS2), Novelose 330 (RS3) and Fibersym (RS4) were also included in the study. The RS content of the PRSF used in this study was in the range of 25–77%. Standardised static in vitro digestion processes were applied, and the total digestibility, GI and BABC of the samples were determined. The digestibility of commercial RS samples was lower than the PRSF samples. No significant correlation was found between digestibility and RS or total dietary fibre (TDF) contents of the samples. A statistically significant positive correlation was obtained between GI and in vitro digestibility values. In addition, there was a statistically significant negative correlation between the GI and TDF content of the PRSF samples. In addition, it was observed that neither RS content nor RS type had a significant effect on BABC.

Women are prone to iron deficiency because of increased iron excretion associated with menstruation. This is often treated by oral iron supplementation, although this treatment can cause side effects, such as stomach pain and nausea, with low absorption of ingested iron. Previously, a significant increase in serum iron was observed in association with the consumption of foods containing Lactococcus lactis subsp. cremoris H61 (H61). However, the causal relationship between H61 ingestion and elevated serum iron is still unclear. Therefore, in this study, we aimed to determine the effects of H61 ingestion on the iron status of young women. Healthy young Japanese women (18–25 years of age) ingested either heat-killed H61 or placebo for 4 weeks. Serum iron, transferrin saturation, and ferritin were significantly elevated in the H61 group but remained unchanged in the placebo group. Compared to before the intervention, iron intake remained unchanged during the intervention period, so the change in the iron status of the H61 group was not due to increased iron intake. These results suggest that heat-killed H61 may elevate iron status by enhancing iron absorption.

Pulses are an affordable source of proteins, starch, lipids, minerals and high value nutritional sources. This study was conducted to evaluate relationship between protein functional properties and their preparation methods. Therefore, the functional properties of Grass pea protein concentrates (GPPC) prepared using isoelectric precipitation (IE), salt extraction (SE) and ultrafiltration-diafiltration methods (UF/D) were determined. The GPP processed by those three precipitation methods contained all of the amino acids which aspartic acid and glutamic acid were dominate amino acids followed by arginine and leucine. However, methionine and tryptophan were limited amino acids. Water binding capacity was in following order: UF/D-GPPC > SE-GPPC > IE-GPPC. Meanwhile, highest value of oil binding capacity belonged to UF/D-GPPC. GPPC prepared using UF/D method had highest solubility. In term of interfacial tension, it was revealed that the interfacial tension of all isolates did not significantly reduced (P > 0/05). Net negative zeta potential with values was observed which IE-GPPC had highest surface charge followed by UF/D-GPPC and SE-GPPC, respectively. In terms of surface hydrophobicity, it was altered in the following order: IE-GPPC > SE-GPPC > UF/D-GPPC. It was observed that foaming capacity ranged between 85.06 and 89.78% and foaming stability ranged between 77.34 and 84.35%. Emulsifying capacity, emulsifying activity index and emulsifying stability index ranged between 105.06–109.78%, 31.09–36.29 m2/g and 12.90–18.86 min respectively. Evaluation of least gelling concentration showed that UF/D-GPPC were capable to form firm gel at low concentration (10% W/V). The functional properties of proteins are influenced by their extraction technique and can be achieve maximum functional characteristics by selecting appropriate extraction method. The results indicated the technological potential of GPP for health-promoting food formulations.

The effect of wet and dry milling on the functional properties of whole sorghum grain flour (SF) and extracted kafirin were assessed. White sorghum landrace was used to prepare two SFs by wet milling (SF1) or dry milling (SF2) and to extract their respective kafirins SK1 and SK2. Protein contents of SK1 and SK2 were 90.07 and 94.23%. Wet milling of SF allowed increasing the oil binding capacity, the least gelling concentration and the instant foam capacity and decreasing the water binding capacity and foam stability. The emulsifying activity index of SF1 and SF2 were in the same range, while emulsion stability was two time higher in SF2. Functional properties of SK1 and SK2 showed an appropriate water binding capacity of 2.20 ± 0.10 and 1.82 ± 0.22 (g water/g dry mater), respectively. Both SK1 and SK2 showed higher oil binding capacity than SF1 and SF2 with no gel and foam formation. The wet milling improved water and oil binding capacities of SK1 by 17 and 5%. The emulsifying activity indexes were approximately similar for SK1 and SK2 with emulsion stability exceeding 60%. Fourier transform infrared spectroscopy of SK1 and SK2 showed that wet milling induced a decrease of α-helical structure and an increase of intermolecular β-sheet and β-turns and no change in the anti parallel β-sheet. This study showed that wet milling could allow extracting kafirin with preserving the most important functional properties of SF and kafirin and could constitute an interesting method for protein recovery and starch isolation.

Objective: The aim of this study was to investigate the effects of supplementation of dietary soluble fibers with high water-binding capacity (WBC) and swelling capacity (SC) on gastrointestinal tract mass, physicochemical properties of digesta, gastrointestinal mean retention time (MRT), body weight, and food intake in male rats. Methods: Thirty-two male Sprague-Dawley rats were randomized to four equal groups and fed the control diet or diet containing 2% konjac flour (KF), pregelatinized waxy maize starch plus guar gum (PWMS+GG), andPWMS plus xanthan gum (PWMS+XG) for three weeks. Results: WBC and SC of diets followed the order of PWMS+GG > KF > PWMS + XG > control. PWMS+GG and KF groups had a lower average daily food intake than the control group, but all the groups showed no difference in final body weightand the weight gain rate. The high WBC and SC of the PWMS+GG and KF groupsled to an increase of WBC and SC in the stomach digesta, and a gain of the cecal digesta weight, due to increased cecal moisture content. Conclusion: The inclusion of the novel fiber, PWMS+GG, in the diet of male rats appears to facilitate the modulation of WBC and SC of stomach digesta and the reduction of food intake.

Due to their nutritional and sensorial characteristics, tropical fruits like guava, mamey sapote, and passion fruit are regularly incorporated into daily diets. Their by-products, especially peels, are approximately 10 to 35% of their weight and possess an important content of bioactive compounds, such as dietary fiber and phenolics. The nutritional, technological, physio-functional properties and phenolic compound compositions of guava, mamey sapote, and passion fruit peels were studied. Peels had promising techno- and physio-functional characteristics, good dietary fiber contents (45.18-61.42 g/100 g), and phenolic profiles with ferulic acid, gallic acid, p-coumaric, and catechin as the main compounds. Peel powders also showed excellent DPPH radical scavenging activity (125.3–252.4 µmol TE/100 g) and Trolox equivalent antioxidant capacity, TEAC (369.2–656.8 µmol TE/100 g). The α-amylase and lipase inhibitory activity varied from 28.15 to 51.4% and 30.89 to 57.15%, respectively. Higher values of α-glucosidase inhibition capacity were found, ranging from 51.64 to 70.32%. The chemical composition and properties reported in the present work suggest that peel powders of these guava, mamey sapote, and passion fruit could be used as constituents in different foods, such as bakery and meat goods, with beneficial health effects like control of hyperglycemia, improved intestinal function, and control of overweight; however, more studies are necessary for animal models and humans to confirm these bioactivities conclusively.

Plastein reaction is a modification reaction that can improve the functional properties of protein hydrolysate. The product of the reaction is a thixotropic aggregation of peptides. This study investigated the formation condition of soybean-whey plastein and bile acid binding capacity of plastein. Soy protein and whey protein were hydrolyzed by pepsin. The mixture (1:1, w/w) of two hydrolysates was modified by pepsin again. After the reaction, the decrease in free amino groups and the turbidity of the modified hydrolysate were measured to obtain appropriate reaction condition. Results showed that the concentration of hydrolysates 40% (w/v), enzyme ratio of 2.0 KU/g protein, pH 5.0, 37 °C, reaction time of 3.0 h respectively, were showed maximum changes in protein hydrolysates. Tricine SDS-PAGE analysis under denaturing conditions revealed that whey protein was more sensitive to pepsin and yielded different polypeptides (PPs) of molecular weight ranged from 3.5–17 kDa. However, a high molecular weight PP was completely hydrolyzed while PPs of 14.2–26 kDa were partially digested after pepsin treatment. Native page analysis further revealed the presence of a high-molecular weight PP in crude and purified plastein product. The bile acid binding capacity was improved by the plastein reaction. The amount of binding sodium deoxycholate, sodium taurocholate, and sodium cholate were 0.75, 2.0 and 1.87 μmol/100 mg respectively.