Effect of pH and pepsin limited hydrolysis on the structure and functional properties of soybean protein hydrolysates

Enhancing the Gelation Behavior of Transglutaminase-Induced Soy Protein Isolate(SPI) through Ultrasound-Assisted Extraction

Gelation, as an important functional property of soy protein isolate (SPI), can be improved by some green technologies in food manufacturing, including ultrasound, ultrahigh pressure and microwave treatments. This work investigated the effect of an alkaline solubilisation step in SPI extraction combined with sonication on protein properties. The TGase-induced gel of the modified SPI was prepared to explore the effect of ultrasound on gel properties, including structures, strength, water-holding capacity and rheological properties. Additionally, the differences between traditional ultrasound modification of SPI and current modification methods were analyzed. The results showed that the ultrasonication-assisted extraction method could result in a significant increase in extraction rate from 24.68% to 42.25%. Moreover, ultrasound-assisted modification of SPI gels induced with transglutaminase (TGase) exhibited significant improvement in mechanical properties, such as texture, water-holding capacity and rheological properties, In particular, SPI extracted at 400 W ultrasound intensity for 180 s showed the best overall performance in terms of gel properties. Our method efficiently uniformizes gel structure, enhancing mechanical properties compared to conventional ultrasound methods, which reduced energy consumption and costs. These findings provide insights into the production of high-gelation SPI in food manufacturing.

Effect of Molecular Weight on the Structural and Emulsifying Characteristics of Bovine Bone Protein Hydrolysate

The emulsifying capacity of bovine bone protein extracted using high-pressure hot water (HBBP) has been determined to be good. Nevertheless, given that HBBP is a blend of peptides with a broad range of molecular weights, the distinction in emulsifying capacity between polypeptide components with high and low molecular weights is unclear. Therefore, in this study, HBBP was separated into three molecular weight components of 10-30 kDa (HBBP 1), 5-10 kDa (HBBP 2), and <5 kDa (HBBP 3) via ultrafiltration, and the differences in their structures and emulsifying properties were investigated. The polypeptide with the highest molecular weight displayed the lowest endogenous fluorescence intensity, the least solubility in an aqueous solution, and the highest surface hydrophobicity index. Analysis using laser confocal Raman spectroscopy showed that with an increase in polypeptide molecular weight, the α-helix and β-sheet contents in the secondary structure of the polypeptide molecule increased significantly. Particle size, rheological characteristics, and laser confocal microscopy were used to characterize the emulsion made from peptides of various molecular weights. High-molecular-weight peptides were able to provide a more robust spatial repulsion and thicker interfacial coating in the emulsion, which would make the emulsion more stable. The above results showed that the high-molecular-weight polypeptide in HBBP effectively improved the emulsion stability when forming an emulsion. This study increased the rate at which bovine bone was utilized and provided a theoretical foundation for the use of bovine bone protein as an emulsifier in the food sector.

High-strength and high-toughness ECM films with the potential for peripheral nerve repair

Extracellular matrix (ECM) scaffolds are widely applied in the field of regeneration as the result of their irreplaceable biological advantages, and the preparation of ECM scaffolds into ECM hydrogels expands the applications to some extent. However, weak mechanical properties of current ECM materials limit the complete exploitation of ECM's biological advantages. To enable ECM materials to be utilized in applications requiring high strength, herein, we created a kind of new ECM material, ECM film, and evaluated its mechanical properties. ECM films exhibited outstanding toughness with no cracks after arbitrarily folding and crumpling, and dramatically high strength levels of 86 ± 17.25 MPa, the maximum of which was 115 MPa. Such spectacular high-strength and high-toughness films, containing only pure ECM without any crosslinking agents and other materials, far exceed current pure natural polymer gel films and even many composite gel films and synthetic polymer gel films. In addition, both PC12 cells and Schwann cells cultured on the surface of ECM films, especially Schwann cells, showed good proliferation, and the neurite outgrowth of the PC12 cells was promoted, indicating the application potential of ECM film in peripheral nerve repair.

Yeast protein as a novel dietary protein source: Comparison with four common plant proteins in physicochemical properties

Currently, with the preference for a healthy diet and increased awareness of reducing the carbon footprint, the demand for protein is becoming more and more diversified. In this study, the physicochemical properties of yeast protein (YP) and four common plant proteins (soy protein isolate, pea protein isolate, wheat gluten, and peanut protein) were compared. The most prevalent secondary structure in YP is the β-sheet. Furthermore, YP is in an aggregated state, and it has a high surface hydrophobicity. The tryptophan residues are primarily exposed on the polar surface of YP. The results of in vitro digestibility indicated that YP (84.91 ± 0.52%) was a high-quality protein. Moreover, YP has a higher thermal stability and relatively stable low apparent viscosity, which provides ample possibility for its application in food processing and in foods for people with swallowing difficulties. This study provides theoretical basis in the potential of YP as an alternative protein source.

Effect of High-Intensity Ultrasound Pretreatment on the Properties of the Transglutaminase (TGase)-Induced β-Conglycinin (7S) Gel

In this study, we investigated the effects of different high-intensity ultrasound (HIU) pretreatment times (0-60 min) on the structure of β-conglycinin (7S) and the structural and functional properties of 7S gels induced by transglutaminase (TGase). Analysis of 7S conformation revealed that 30 min HIU pretreatment significantly induced the unfolding of the 7S structure, with the smallest particle size (97.59 nm), the highest surface hydrophobicity (51.42), and the lowering and raising of the content of the α-helix and β-sheet, respectively. Gel solubility showed that HIU facilitated the formation of ε-(γ-glutamyl)lysine isopeptide bonds, which maintain the stability and integrity of the gel network. The SEM revealed that the three-dimensional network structure of the gel at 30 min exhibited filamentous and homogeneous properties. Among them, the gel strength and water-holding capacity were approximately 1.54 and 1.23 times higher than those of the untreated 7S gels, respectively. The 7S gel obtained the highest thermal denaturation temperature (89.39 °C), G', and G″, and the lowest tan δ. Correlation analysis demonstrated that the gel functional properties were negatively correlated with particle size and the α-helix, while positively with Ho and β-sheet. By contrast, gels without sonication or with excessive pretreatment showed a large pore size and inhomogeneous gel network, and poor properties. These results will provide a theoretical basis for the optimization of HIU pretreatment conditions during TGase-induced 7S gel formation, to improve gelling properties.

Developing rumen mimicry process for biological ammonia synthesis

The ruminant rumen houses hyper-ammonia-producing bacteria (HAB) that produce ammonia with minimal energy use. Here we developed a mimicry process to produce bio-ammonia, a solution of ammonia and ammonium. The rumen microbes were used to ferment soybean (SYB), soybean protein isolate (SPI), and pepsin-hydrolysate (HP) for bio-ammonia production. The maximum bio-ammonia produced from SYB, SPI, and HP were 0.65, 1.2_, and 1.1 g/L, respectively. The presence of non-protein in SYB hindered bio-ammonia production and the processing of SYB to SPI and HP significantly (p < 0.05) increased bio-ammonia production. HP was converted to bio-ammonia quicker than SPI suggesting that enzymatic hydrolysis increases bioprocessing efficiency. Metagenomic analysis of a sample culture revealed that the HAB population is predominantly Klebsiella quasivariicola (73%), Escherichia coli (6%), and Enterobacter cloacae (6%). The bioprocessing steps developed would enable industrial ammonia production to achieve a low CO₂ footprint.

Purification and characterization of aspartic protease from Aspergillus niger and its efficient hydrolysis applications in soy protein degradation

BACKGROUND

Adding acid protease to feed can enhance protein digestibility, boost feed utilization, and stimulate the growth of animals in breading industry. In order to obtain an acid protease with high hydrolysis efficiency to plant protein, in this study, an aspartic protease from Aspergillus niger was heterologous expressed in Pichia pastoris (P. pastoris). The enzymatic properties and application in soybean protein degradation were also studied.

RESULTS

In our investigation, the high aspartic protease (Apa1) activity level of 1500 U/mL was achieved in 3 L bioreactor. After dialysis and anion exchange chromatography, the total enzyme activity and specific enzyme activity were 9412 U and 4852 U/mg, respectively. The molecular weight of the purified protease was 50 kDa, while the optimal pH and temperature were 3.0 and 50 °C, respectively. It was stable at pH 2.0-5.0 and 30-60 °C. Apa1 was used to hydrolyze soybean isolate protein (SPI) at 40 °C and pH 3.0, and a high hydrolysis degree (DH) of 61.65% was achieved. In addition, the molecular weight distribution of SPI hydrolysis products was studied, the result showed that the hydrolysis products were primarily oligopeptides with molecular weights of 189 Da or below.

CONCLUSIONS

In this study, Apa1 was successfully expressed in P. pastoris and high expression level was obtained. In addition, the highest protein hydrolysis rate to SPI degradation so far was achieved. The acid protease in this study provides a new protease that is suitable for the feed industry, which will be very helpful to improve the feed utilization and promote the development of the breeding industry.

Walnut Protein Isolate-κ-Carrageenan Composite Gels Improved with Synergetic Ultrasound-Transglutaminase: Gelation Properties and Structure

Walnut protein is a kind of natural, high-quality plant protein resource. However, its high content of gluten, strong hydrophobicity and poor gelation ability have greatly limited its development and utilization in gel products. It was found in this experiment that ultrasonic power combined with transglutaminase (TGase) had a significant effect on the gel properties of the walnut protein isolate (WNPI)-κ-carrageenan (KC) complex. The results showed that the gel strength of the WNPI-KC complex first increased and then decreased with the increase in ultrasonic power (0-400 W). WNPI-KC composite gel had the best texture properties, rheological properties, water-holding capacity (99.41 ± 0.76%), swelling ratio (2.31 ± 0.29%) and thermal stability (83.22 °C) following 200 W ultrasonic pretreatment. At this time, the gel network was more uniform and much denser, and the water molecules were more tightly bound. Further, 200 W ultrasonic pretreatment could promote the transformation of α-helices to β-folds in protein molecules, improve the fluorescence intensity, increase the content of free sulfhydryl groups and enhance the intermolecular forces. The experimental results could provide technical support for the development of walnut protein gel food.

The role of the extension region on the structural and physicochemical characteristics of the α-subunit of β-conglycinin: implications of pH value and ionic strength

BACKGROUND

To clarify the role of the extension region on the structure-functional relationship of the α-subunit of β-conglycinin, α-subunit and its segment of the core region (αc-subunit) were expressed via an Escherichia coli system. Their physicochemical properties were compared under acid, neutral or alkaline conditions (pH 4.0, 7.0, and 8.0) and high or low ionic strength (μ = 0.05 and 0.5), respectively.

RESULTS

The results showed that the extension region contributed to increasing thermal stability, especially at low ionic strength under acidic and neutral conditions. The extension region stabilized the α-subunit with high solubility, low turbidity, and small particle size under neutral and alkaline conditions, whereas these impacts were suppressed at a high ionic strength and acidic conditions. Surface hydrophobicity of the α-subunit decreased under acidic and alkaline conditions without being interfered with by ionic strength.

CONCLUSION

It can be concluded that the extension region played different roles under different pH and ionic strength conditions. These factors should be specified carefully and speculated individually to explore the more detailed and profound nature of β-conglycinin at the submolecular level. The results could benefit a better understanding of the relationship between domain structure and functions of soybean protein. © 2022 Society of Chemical Industry.

Enzymatic hydrolysates of soy protein promote the physicochemical stability of mulberry anthocyanin extracts in food processing

Soy protein papain hydrolysate (SPAH) and soy protein pepsin hydrolysate (SPEH) were used as protective agents for mulberry anthocyanin extracts (MAEs) to inhibit its color fading and enhance the anthocyanin stability at pH 6.3. Both SPAH and SPEH showed a significant protective effect on total anthocyanins in MAEs solutions. 1.0 mg/mL of SPEH presented the best protective effect on MAEs by increasing its half-life from 1.8 to 5.7 days. SPAH/SPEH-cyaniding-3-O-glucoside (C3G) interactions were investigated at pH 6.3 by fluorescence, Fourier-transform infrared spectroscopy (FT-IR), and Circular Dichroism (CD). Their association was mainly driven by hydrophobic interactions, and SPEH showed a higher binding affinity for C3G than SPAH, with a KA value of 2.62 × 105 M-1 at 300 K. The second structures of SPAH and SPEH were altered by C3G, with a decrease in the β-sheets and an increase in the turns and random coils.

Effect of Coconut Protein and Xanthan Gum, Soybean Polysaccharide and Gelatin Interactions in Oil-Water Interface

We report on our study of the interactions between coconut protein extracted from coconut meat and three hydrocolloids (gelatin, xanthan gum, and soybean polysaccharide) and their interfacial adsorption and emulsification properties. We used Zeta potential, fluorescence spectroscopy scanning and ITC to investigate the interactions between a fixed concentration (1%) of coconut protein and varying concentrations of hydrocolloid. Through the interfacial tension and interfacial viscoelasticity, the interfacial properties of the hydrocolloid and coconut protein composite solution were explored. The physical stability of the corresponding emulsion is predicted through microstructure and stability analysis. Xanthan gum forms a flocculent complex with coconut protein under acidic conditions. Soy polysaccharides specifically bind to coconut protein. Under acidic conditions, this complex is stabilized through the steric hindrance of soy polysaccharides. Due to gelatin-coconut protein interactions, the isoelectric point of this complex changes. The interfacial tension results show that as time increases, the interfacial tensions of the three composite solutions decrease. The increase in the concentration of xanthan gum makes the interfacial tension decrease first and then increase. The addition of soybean polysaccharides reduces the interfacial tension of coconut protein. The addition of xanthan gum forms a stronger elastic interface film. Emulsion characterization showed that the gelatin-added system showed better stability. However, the addition of xanthan gum caused stratification quickly, and the addition of soybean polysaccharides also led to instability because the addition of polysaccharides led to a decrease in thermodynamic compatibility. This research lays the foundation for future research into coconut milk production technology.

Influence of pH and temperature on the physicochemical and functional properties of Bambara bean protein isolate

Bambara bean is a rich low-cost protein source and a functional ingredient in the food industry. We investigated the effects of temperature and different pH on the physicochemical and functional properties of Bambara bean protein isolate. Vicilin was the major protein of Bambara bean as revealed by SDS PAGE analysis. The emulsifying capacity of protein isolate was highest at 80 °C, pH 9 while emulsion stability was highest at pH 4. Generally, increase in temperature decreased protein solubility at pH 4 and 7, while increase was observed at pH 9 and 100 °C. The hydrophobicity of isolate was highest at pH 4 and lowest at pH 9, regardless of temperature. Protein isolate possessed highly compact β-sheet and α-helix secondary structures in proportions greater than 75% (at pH 9 and 50 °C). Increase in temperature generally promoted protein rearrangement and partial unfolding. Protein secondary structure and surface hydrophobicity can predict food functionality, directly affecting protein behavior during formulation and long-term storage. This study clearly demonstrated the potential of exploiting pulse protein isolates as nutritional and functional ingredients through temperature and pH control.

Study of biological activities and physicochemical properties of Yamú (Brycon siebenthalae) viscera hydrolysates in sodium alginate-based edible coating solutions

The fishing industry produces waste such as viscera, which is an environmental problem for many countries. Obtaining protein from these wastes are useful for the food industry. In this study, the chemical composition, amino acid profile, solubility, digestibility and thermal properties of Yamú protein isolate (PI) and its hydrolysates obtained by enzymatic hydrolysis were characterized. The hydrolysates (0.05, 0.1, 0.5, 1 and 2% w/v) were mixed with a sodium alginate-based solution to form an edible coating solution (ECS). Antioxidant capacity antimicrobial activity, Zeta potential (ζ) and adsorption kinetics properties were determined. PI contains 88% (w/w) protein showing better solubility, digestibility and thermal stability properties. The hydrolysate concentrations with DPPH inhibitory ECS were 0.1 and 0.5% (w/v). The kinetic properties of ECS showed good stability and excellent adsorption. These results suggest that this Yamú protein has high nutritional potential as an ingredient for the production of functional foods.

Influence of ultrasound-assisted ionic liquid pretreatments on the functional properties of soy protein hydrolysates

In this work, the effect of dual-frequency ultrasound-assisted ionic liquids (ILs) pretreatment on the functional properties of soy protein isolate (SPI) hydrolysates was investigated. The degree of hydrolysis (DH) of SPI pretreated by ultrasound and [BMIM][PF₆] increased by 12.53% as compared to control (P < 0.05). More peptides with low molecular weight were obtained, providing support for the changes in DH. The trichloroacetic acid-nitrogen soluble index presented an increase, suggesting a better protein hydrolysate property. The increase in the calcium-binding activity showed the ultrasound-assisted ILs pretreatment could potentially improve bone health. The foaming capacity and stability of SPI hydrolysates pretreated by ultrasound-assisted [BMIM][PF₆] always increased remarkably as compared to ultrasound-assisted [BDMIM][Cl] pretreatment. However, the synergistic effect of ultrasound-assisted [BMIM][PF₆] on the emulsifying activity and antioxidant activities (DPPH and hydroxyl radical scavenging activity) was not as ideal as ultrasound-assisted [BDMIM][Cl] pretreatment, which may be affected by the structure of peptide. In conclusion, these results indicated the combination of dual-frequency ultrasound and ionic liquids would be a promising method to improve the functional properties of SPI hydrolysates and broaden the application scope of compound modification in proteolysis industry.

Effect of enzymatic hydrolysis on the formation and structural properties of peanut protein gels

The limited enzymatic hydrolysis gelation method was investigated using peanut protein isolate (PPI) without any coagulators. A peanut protein gel could be formed by enzyme treatment with Alcalase at low temperature (50–70 °C). The influence of enzymatic hydrolysis on the rheological and physicochemical properties was investigated. Structural changes in the PPI were characterized by analyzing the subunits, chemical forces, surface hydrophobicity, fluorescence spectra, and circular dichroism (CD) spectra. The results revealed that enzymatic hydrolysis significantly affected the conarachin II protein of PPI, and had little influence on conarachin I and the basic subunits of arachin. Hydrophobic interaction was the main chemical force active in the peanut protein gel. An increase in the surface hydrophobicity coupled with red-shifts of the fluorescence spectra indicated that inner hydrophobic regions were exposed after hydrolysis, resulting in gel formation via hydrophobic interactions. The CD spectra showed that significant changes occurred in the secondary structure of PPI, where the ordered PPI structure formed a more open structure after enzymatic hydrolysis.

Biochemical characterization of two new Aspergillus niger aspartic proteases

Two new aspartic proteases, PepAb and PepAc (encoded by pepAb and pepAc), were heterologously expressed and biochemically characterized from Aspergillus niger F0215. They possessed a typical structure of pepsin-type aspartic protease with the conserved active residues D (84, 115), Y (131, 168) and D (281, 326), while their identity in amino acid sequences was only 19.0%. PepAb had maximum activity at pH 2.5 and 50 °C and PepAc at 3.0 and 50 °C. The specific activities of PepAb and PepAc toward casein were 1368.1 and 2081.4 U/mg, respectively. Their activities were significantly promoted by Cu²⁺ and Mn²⁺ and completely inhibited by pepstatin. PepAb exhibited higher catalytic efficiency (k _cat/K _m) toward soy protein isolates than casein, while PepAc showed higher catalytic efficiency toward casein. The hydrolysis capacities of PepAb and PepAc on soy protein isolates were slightly lower than that of previously identified A. niger aspartic protease, PepA (aspergillopepsin I), while the resultant peptide profiles were remarkably different for all three proteases.

Natural Macromolecules as Carriers for Essential Oils: From Extraction to Biomedical Application

Essential oils (EOs) and their main constituents, the terpenes, are widely studied, mostly relating to their antioxidant ability and bioactivity, such as antimicrobial, anticancer, anti-inflammatory, and range of other actions in the living systems. However, there is limited information on their bioavailability, especially upon clinical studies. Having in mind both strong biological effects and health benefits of EOs and their specific physicochemical properties (volatility, lipophilic character, low water solubility or insolubility, viscosity, expressed odor, concentration-dependent toxicity, etc.), there is a need for their encapsulation for target delivery. Encapsulation of EOs and their constituents is the prerequisite for enhancing their oxidative stability, thermostability, photostability, shelf life, and biological activity. We considered various carrier types such a (1) monophase and polyphase polysaccharide hydrogel carriers, (2) polysaccharide-protein carriers, and (3) lipid carriers in the context of physicochemical and engineering factors. Physicochemical factors are encapsulation efficiency, chemical stability under gastric conditions, mechanical stability, and thermal stability of carrier matrices. Choice of carrier material also determines the encapsulation technique. Consequently, the engineering factors are related to the advantage and disadvantage of various encapsulation techniques frequently used in the literature. In addition, it was intended to address the interactions between (1) main carrier components, such as polysaccharides, proteins, and lipids themselves (in order to form chemically and mechanically stable structure); (2) main carrier components with pepsin under gastric conditions (in order to form resistant material under gastric conditions); and (3) main carrier components with EOs (in order to enhance encapsulation efficiency), as a necessary precondition for whole process optimization. Finally, different sources for obtaining natural carrier macromolecules are surveyed, especially the agro-waste materials and agricultural and food by-products. This review article highlights the bioavailability aspects of encapsulated EOs and physicochemical and engineering factors concerning natural macromolecule carriers for their target delivery and application.

Localized enzymolysis and sonochemically modified sunflower protein: Physical, functional and structure attributes

Impacts of localized enzymolysis and sonication on physical, techno-functional, and structure attributes of sunflower meal protein (SMP) and its hydrolysate (SMPH) were studied. SMP was subjected to enzymolysis (using alcalase) to prepare SMPH with various degrees of hydrolysis (6-24% DH). Enzymolysis decreased colour lightness, turbidity, and particle size of unsonicated and sonicated SMP, while it increased the absolute values of zeta potential (P < 0.05). Sonication improved oil absorption capacity and dispersibility over unsonicated samples. Contrarily, sonicated preparations showed a decrease in water holding capacity. Intrinsic fluorescence and FTIR spectral analyses suggested that SMPH had more movable/flexible secondary structures than SMP. Moreover, the changes in sulfhydryl clusters and disulfide linkages following sonication demonstrated limited unfolding of SMP and SMPH structure and decrease in intermolecular interactions. SDS-PAGE profile exhibited significant reduction in molecular weight (MW) of sonicated SMP, whereas did not display differences between unsonicated and sonicated SMPH. From further MW analysis, SMPH was categorized with high proportion of small-sized peptides ≤ 3 kDa fractions, which increased from 78.64 to 93.01% (control) and from 82.3 to 93.88% (sonication) with enzymolysis (6-24DH). Localized enzymolysis and sonication can be utilised to modify the physical and conformational attributes of SMP and SMPH, which could enhance their functionalities and broaden the utilisation area in food industry.

Effects of High Pressure Modification on Conformation and Digestibility Properties of Oyster Protein

To expand the utilization of oyster protein (OP), the effects of high pressure (100 to 500 MPa) on chemical forces, structure, microstructure, and digestibility properties were investigated. High pressure (HP) treatment enhanced the electrostatic repulsion (from -13.3Control to -27.8HP200 mV) between protein molecules and avoided or retarded the formation of protein aggregates. In addition, the HP treated samples showed uniform distribution and small particle size. The changes in electrostatic interaction and particle size contributed to the improvement of solubility (from 10.53%Control to 19.92%HP500 at pH 7). The stretching and unfolding of protein were modified by HP treatment, and some internal hydrophobic groups and -SH groups were exposed. HP treatment modified the secondary structure of OP. The treated samples contained less α-helix and β-sheet structures, whereas the proportions of β-sheet and random coil structures were increased. The treated samples have high digestibility in the stomach (from 26.3%Control to 39.5%HP500) and in the total digestive process (from 62.1%Control to 83.7%HP500). In addition, the total digestive production showed higher percentages of small peptides (<1 kDa) after HP treatment. The protein solubility and digestibility were increased after HP treatment, and high solubility and high digestibility might increase the chance that OP become a kind of protein supplement.

Phosphorylation and Enzymatic Hydrolysis with Alcalase and Papain Effectively Reduce Allergic Reactions to Gliadins in Normal Mice

Gliadins are major allergens responsible for wheat allergies. Food processing is an effective strategy to reduce the allergenicity of gluten. In the present study, we determined the secondary and tertiary structures of gluten and gliadins treated by chemical, physical, and enzymatic means through FTIR, surface hydrophobicity, intrinsic fluorescence spectra, and UV absorption spectra. The results showed that the three treatments of phosphorylation and alcalase and papain hydrolyses significantly changed the conformational structures of gliadins, especially the secondary structure. Then, the potential allergenicity of the phosphorylated and alcalase and papain hydrolyzed gliadins were further characterized, and we observed a significant decrease in the allergenicity through the results of the index of spleen, serum total IgE, gliadin-specific IgE, histamine, and serum cytokine concentrations. An elevation of Th17 cells, the absence of Treg cells, and an imbalance in Treg/Th17 are associated with allergy. On the basis of the expression levels of related cytokines and key transcription factors, we also confirmed that phosphorylation and alcalase and papain hydrolysis could effectively reduce the allergenicity of gliadins by improving the imbalance of both Th1/Th2 and Treg/Th17 in the spleens of sensitized mice. This study suggested that the changes in conformational structure contribute to gliadin hyposensitization and that phosphorylation and alcalase and papain hydrolysis may be promising strategies for the production of wheat products with low allergenicity.

Effects of different satiety levels on the fate of soymilk protein in gastrointestinal digestion and antigenicity assessed by an in vitro dynamic gastrointestinal model

The effects of different satiety levels on soymilk protein digestion and antigenicity have been evaluated by an in vitro dynamic gastrointestinal model.

Production and characterization of cowpea protein hydrolysate with optimum nitrogen solubility by enzymatic hydrolysis using pepsin

BACKGROUND

Cowpea is a source of low-cost and good nutritional quality protein for utilization in food formulations in replacement of animal proteins. Therefore it is necessary that cowpea protein exhibits good functionality, particularly protein solubility which affects the other functional properties. The objective of this study was to produce cowpea protein hydrolysate exhibiting optimum solubility by the adequate combination of hydrolysis parameters, namely time, solid/liquid ratio (SLR) and enzyme/substrate ratio (ESR), and to determine its functional properties and molecular characteristics.

RESULTS

A Box-Behnken experimental design was used for the experiments, and a second-order polynomial to model the effects of hydrolysis time, SLR and ESR on the degree of hydrolysis and nitrogen solubility index. The optimum hydrolysis conditions of time 208.61 min, SLR 1/15 (w/w) and ESR 2.25% (w/w) yielded a nitrogen solubility of 75.71%. Protein breakdown and the peptide profile following enzymatic hydrolysis were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and size exclusion chromatography. Cowpea protein hydrolysate showed higher oil absorption capacity, emulsifying activity and foaming ability compared with the concentrate.

CONCLUSION

The solubility of cowpea protein hydrolysate was adequately optimized by response surface methodology, and the hydrolysate showed adequate functionality for use in food. © 2016 Society of Chemical Industry.

Evaluation of the Hydrolysis Specificity of an Aminopeptidase from Bacillus licheniformis SWJS33 Using Synthetic Peptides and Soybean Protein Isolate

The substrate specificity of aminopeptidases has often been determined against aminoacyl-p-nitroanilide; thus, its specificity toward synthetic peptides and complex substrates remained unclear. The hydrolysis specificity of an aminopeptidase from Bacillus licheniformis SWJS33 (BLAM) was evaluated using a series of synthetic peptides and soybean protein isolate. The aminopeptidase showed high specificity for dipeptides with Leu, Val, Ala, Gly, and Phe at the N-terminus, and the specificity was significantly affected by the nature of the penultimate residue. In the hydrolysis of soy protein isolate, BLAM preferred peptides with Leu, Glu, Gly, and Ala at the N-terminus by free amino acid analysis and preferred peptides with Leu, Ala, Ser, Trp, and Tyr at the N-terminus by UPLC-MS/MS. The introduction of complex substrates provides a deeper understanding of the aminopeptidase's specificity, which can instruct the application of the enzyme in protein hydrolysis.

Pilot-scale whole-cell biocatalysis for the hydroxylation of cyclosporine derivative, FR901459, at higher concentrations by Lentzea sp. 7887 using soybean flour as a novel substrate dispersant

Pilot-scale hydroxylation of FR901459, an immunosuppressive cyclosporine derivative, was performed using resting cells of a Gram-positive bacteria Lentzea sp. 7887 (as whole-cell biocatalysts) and soybean flour as a substrate dispersant. Through biocatalysis, FR901459 was hydroxylated at position 9, producing AS1837812, an important intermediate in the production of drug candidates against hepatitis C. Since FR901459 is insoluble in water, the conversion ratio ([moles of AS1837812 produced/moles of FR901459 added]×100) of the biocatalysis decreased under conditions with substrate concentrations higher than 0.615 mM. To increase the concentration of FR901459 for biocatalysis, we screened various materials to effectively disperse FR901459 in the biocatalysis mixture and found that soybean flour was the best substrate dispersant. The addition of soybean flour to the biocatalysis mixture increased the FR901459 concentration in a 3-L reactor up to 3-fold (1.85 mM). Thus, we successfully established a pilot-scale (1-m3) biocatalysis with a 2-fold higher concentration (1.23 mM) of FR901459 using soybean flour as the substrate dispersant and obtained 419 g of AS1837812 at a conversion ratio of 34.5% in a 28-h batch reaction. Soybean flour can be used as a substrate dispersant for various industrial biocatalysis processes because of its low cost, high availability, and low environmental impact.