Hydrolysis of whey protein isolate in a tangential flow filter membrane reactor

IMPROVEMENT OF THE METHOD OF COMPARATIVE STUDY OF MILK WHEY PROTEINS ENZYMATIC HYDROLYSIS

Milk whey proteins are valueble nutritional ingredients with a number of health-beneficial properties. Whey proteins are also a source of bioactive peptides that can be released in the process of proteins enzymatic hydrolysis. In this connection, there often is a need to compare their proteolytic action on milk whey proteins. It is important to take into account the specificities of the composition and properties of milk whey proteins. The aim of the research was to improve the method of comparative study of milk whey proteins enzymatic hydrolysis. Casein and whey were obtained from fresh cow skimmed milk. The whey was separated by centrifugation after casein precipitation at the isoelectric point. The following enzyme preparations were used in the research: neutral protease, papain, trypsin, chymotrypsin and pancreatin. To select β-LG, gel filtration of the milk whey on the chromatographic column with Sephadex G-150 (Pharmacia) was used. The homogeneity of the received β-LG preparation was analyzed by express electrophoresis in the polyacrylamide gel plates (PAG). The preparation of general casein was isolated by repeated precipitation at the isoelectric point. The fractional composition of the casein substrate was analyzed by electrophoresis in the anode system of homogeneous PAG in the presence of urea. Quantitative treatment of electrophoregrams of the β-LG preparation was performed using the imread reading function. Determination of proteolytic activity of enzyme preparations was carried out according to the method of V. F. Selemenev [6]. In the course of the research, it was determined, that for the research of proteolysis under conditions of identical total proteolytic activity, the concentration of neutral protease should be increased by 1.02 times, papain – by 4.2 times, trypsin – by 2.8 times, pancreatin – by 2.12 times as compared to chymotrypsin. As a result, it has been shown that the use of β-lactoglobulininstead of serum albumin in spectrophotometric determinations allows obtaining more accurate values of the concentrations of whey protein and proteolytic products. In determining the ratio of enzyme : substrate it is advisable to take into account the general proteolytic activity of various enzyme preparations in comparative studies of whey proteins proteolysis with various enzyme preparations. These will simplify the methodology and reduce the time for objective evaluation of enzymatic preparations for proteolysis of milk whey proteins. In some cases, considering the specificity of proteases it could increase the yield of biologically active peptides.

Utilization of blood by-products: An in silico and experimental combined study for BSA usage

In order to exploit industrial discards, protein enzymatic hydrolysis is a currently popular methodology for obtaining bioactive peptides. However, once released, most promising peptides have to be selected from the mixture. In this work, the suitability of pepsin (EC 3.4.23.1) to hydrolyse serum albumin in order to obtain bioactive peptides was assessed. Then, a suitable process to obtain best separation of bioactive peptides was evaluated, using polyethersulfone membranes at different pH values. Serum albumin was easily hydrolysed by pepsin, reaching a DH value of the 65.64 ± 1.57% of the maximum possible. A 23.25% of the identified peptides possessed high bioactivity scores (greater than 0.5), and one of them had reported bioactivity (LLL). Charge mechanisms always predominated over the sieve effect, and best transmission was accomplished at pH values close to the peptides isoelectric points. Basic and neutral peptides with the highest scores were always the most transmitted. Membrane material had greater influence than NMWCO in determining peptide transmission. In order to obtain purified fractions rich in peptides with high bioactivity scores from serum albumin, polyethersulfone membranes (applicable to industrial scale) of 5 kDa MWCO should be used at basic pH values after pepsin digestion.

Separation of Antioxidant Peptides from Pepsin Hydrolysate of Whey Protein Isolate by ATPS of EOPO Co-polymer (UCON)/Phosphate

An aqueous two-phase system (ATPS) consisting of poly(ethylene glycol-ran-propylene glycol) monobutyl ether (UCON)/phosphate was developed for the separation of the antioxidant peptides from pepsin hydrolysate of Whey Protein Isolate (WPI). The efficiency of the separation was evaluated based on the DPPH radical scavenging activity, ABTS radical scavenging activity and ferric reducing antioxidant power (FRAP) of the separated peptides. The effects of some parameters on the partition of antioxidant peptides were investigated. An efficient separation of antioxidant peptides was achieved using ATPS with pH of 4.0, 4 mL of UCON solution (40%, w/w), 4 mL of KH₂PO₄ solution (15.5%, w/w), 2 mL of WPI hydrolysate and 0.40 g/10 mL of NaCl. Reversed-phase high-performance liquid chromatography (RP-HPLC), amino acid analyzer and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to characterize the purified peptides separated by the ATPS. The peptides in top phase were less polar than those in bottom phase. More antioxidative and hydrophobic amino acids were extracted to the top phase of ATPS, and the peptides with the amino acid sequences with antioxidant activities moved to the top phase as well. In conclusion, antioxidant peptides were successfully separated from the WPI hydrolysate by UCON/phosphate ATPS.

Impact of the environmental conditions and substrate pre-treatment on whey protein hydrolysis: A review

Proteins in solution are subject to myriad forces stemming from interactions with each other as well as with the solvent media. The role of the environmental conditions, namely pH, temperature, ionic strength remains under-estimated yet it impacts protein conformations and consequently its interaction with, and susceptibility to, the enzyme. Enzymes, being proteins are also amenable to the environmental conditions because they are either activated or denatured depending on the choice of the conditions. Furthermore, enzyme specificity is restricted to a narrow regime of optimal conditions while opportunities outside the optimum conditions remain untapped. In addition, the composition of protein substrate (whether mixed or single purified) have been underestimated in previous studies. In addition, protein pre-treatment methods like heat denaturation prior to hydrolysis is a complex phenomenon whose progression is influenced by the environmental conditions including the presence or absence of sugars like lactose, ionic strength, purity of the protein, and the molecular structure of the mixed proteins particularly presence of free thiol groups. In this review, we revisit protein hydrolysis with a focus on the impact of the hydrolysis environment and show that preference of peptide bonds and/or one protein over another during hydrolysis is driven by the environmental conditions. Likewise, heat-denaturing is a process which is dependent on not only the environment but the presence or absence of other proteins.

Hydrolysis of wheat gluten by combining peptidases of Flammulina velutipes and electrodialysis

Wheat gluten hydrolysis, used to generate seasonings, was studied using peptidases from Flammulina velutipes or commercial Flavourzyme. L-amino acids were added in a range from 0.5 to 75.0 mM, and L-isoleucine, L-leucine, L-valine, and L-phenylalanine were identified as the strongest inhibitors for both enzyme mixtures. L-serine inhibited Flammulina velutipes peptidases only, while L-histidine and L-glutamine inhibited Flavourzyme peptidases only. To reduce product inhibition by released L-amino acids, electrodialysis was explored. An increase of the degree of hydrolysis of up to 60% for Flammulina velutipes peptidases and 31% for Flavourzyme compared to that for the best control batch was observed after applying an electrodialysis unit equipped with an ultrafiltration membrane for two times 1 h during the 20 h of hydrolysis. The total transfer of free L-amino acids into the concentrate reached 25-30% per hour. Peptides passed the membrane less easily, although the nominal cutoff was 4 kDa.

Review: Production and functionality of active peptides from milk

In recent years, research on the production of active peptides obtained from milk and their potential functionality has grown, to a great extent. Bioactive peptides have been defined as specific protein fragments that have a positive impact on body functions or conditions, and they may ultimately have an influence on health. Individual proteins of casein or milk-derived products such as cheese and yogurt have been used as a protein source to study the isolation and activity of peptides with several applications. Currently, the milk whey waste obtained in the production of cheese also represents a protein source from which active peptides could be isolated with potential industrial applications. The active properties of milk peptides and the results found with regard to their physiological effects have led to the classification of peptides as belonging to the group of ingredients of protein nature, appropriate for use in functional foods or pharmaceutical formulations. In this study, the main peptides obtained from milk protein and the past research studies about its production and biological activities will be explained. Second, an analysis will be made on the methods to determinate the biological activities, the separation of bioactive peptides and its structure identification. All of these form the base required to obtain synthetic peptides. Finally, we explain the experimental animal and human trials done in the past years. Nevertheless, more research is required on the design and implementation of equipment for the industrial production and separation of peptides. In addition, different authors suggest that more emphasis should therefore be given to preclinical studies, proving that results are consistent and that effects are demonstrated repeatedly by several research human groups.

Continuous hydrolysis of modified wheat gluten in an enzymatic membrane reactor

BACKGROUND

The low solubility of wheat gluten is one of the major limitations to its use in food processing, and enzymatic hydrolysis has been found to be an effective way to prepare more soluble bioactive peptides from gluten. The aim of this study was to prepare bioactive peptides from modified wheat gluten (MWG) in a continuous enzymatic membrane reactor (EMR) that allowed rapid separation of low-molecular-weight peptides from hydrolysates, thus avoiding the disadvantages of batch reaction such as inefficient use of enzymes, inconsistent products due to batch-to-batch variation, substrate-product inhibition, low productivity and excessive hydrolysis.

RESULTS

Wheat gluten was modified to decrease its lipid and starch contents in order to prevent membrane fouling. The optimal working conditions for Alcalase to hydrolyse MWG in the EMR were a substrate concentration of 20 g L(-1) , an enzyme/substrate ratio of 0.03, an operating pressure of 0.04 MPa, a temperature of 40 °C and a pH of 9. The operating stability of the EMR (including residual enzyme activity, productivity and capacity) was high. The permeate fractions showed antioxidant activities that were mostly due to low-molecular-weight peptides. A simple theoretical kinetic model was successfully applied to the enzymatic hydrolysis of MWG in the EMR.

CONCLUSION

Modification of wheat gluten made the continuous enzymatic membrane reaction more efficient and the EMR proved to be an effective means of producing peptides with particular properties and bioactivities. The permeate fractions (mainly < 1000 Da) were homogeneous and stable and also showed strong antioxidant activities.

Preparation of whey protein hydrolysates using a single- and two-stage enzymatic membrane reactor and their immunological and antioxidant properties: characterization by multivariate data analysis

An initial 5% (w/v), followed thereafter with replacement aliquots of 3% (w/v), whey protein isolate (WPI) (ca. 86.98% Kjeldahl N x 6.38), was hydrolyzed using Protease N Amano G (IUB 3.4.24.28, Bacillus subtilis) in an enzymatic membrane reactor (EMR) fitted with either a 10 or 3 kDa nominal molecular weight cutoff (NMWCO) tangential flow filter (TFF) membrane. The hydrolysates were desalted by adsorption onto a styrene-based macroporous adsorption resin (MAR) and washed with deionized water to remove the alkali, and the peptides were desorbed with 25, 50, and 95% (v/v) ethyl alcohol. The desalted hydrolysates were analyzed for antibody binding, free radical scavenging, and molecular mass analysis as well as total and free amino acids (FAA). For the first time a quantity called IC50, the concentration of peptides causing 50% inhibition of the available antibody, is introduced to quantify inhibition enzyme-linked immunosorbent assay (ELISA) properties. Principal component analysis (PCA) was used for data reduction. The hydrolysate molecular mass provided the most prominent influence (PC1 = 57.35%), followed by inhibition ELISA (PC2 = 18.90%) and the antioxidant properties (PC3 = 10.43%). Ash was significantly reduced in the desalted fractions; the protein adsorption recoveries were high, whereas desorption with alcohol was prominently influenced by the hydrophobic/ hydrophilic amino acid balance. After hydrolysis, some hydrolysates showed increased ELISA reactivity compared with the native WPI.