The use of serine protease from Yarrowia lipolytica yeast in the production of biopeptides from denatured egg white proteins.

Deriving non-conventional enzymes from cheaper sources than those used for commercially available enzymes may result in the production of hydrolysates with beneficial features, while drastically reducing the cost of hydrolysis. This is especially significant for enzymatic hydrolysis as a method of protein waste utilization. We have previously described the ability of non-commercial serine protease from Yarrowia lipolytica yeast to produce/release bioactive peptides from egg white protein by-products (EP). The enzymatic hydrolysis of EP was carried out for 24 h using the serine protease at an enzyme: substrate ratio of 1:30 (w/w). The obtained hydrolysate was characterized by protein degradation of 38% and also exhibited an antioxidant and cytokine-inducing activity. The isolation procedure (ultrafiltration and RP-HPLC) of bioactive peptides from the EP hydrolysate provided peptide fractions with significant antioxidant and ACE inhibitory activities. Three homogeneous and three heterogeneous peptide fractions were identified using MALDI-TOF/MS and the Mascot Search Results database. The peptides, mainly derived from ovalbumin, were composed of 2-19 amino-acid residues. We have thus demonstrated a novel ability of serine protease from Y. lipolytica to release biopeptides from an EP by-product.

Egg-yolk protein by-product as a source of ACE-inhibitory peptides obtained with using unconventional proteinase from Asian pumpkin (Cucurbita ficifolia).

In the present study angiotensin I-converting enzyme (ACE) inhibitory peptides were isolated from egg-yolk protein preparation (YP). Enzymatic hydrolysis conducted using unconventional enzyme from Cucurbita ficifolia (dose: 1000 U/mg of hydrolyzed YP (E/S (w/w)=1:7.52)) was employed to obtain protein hydrolysates. The 4-h hydrolysate exhibited a significant (IC50=482.5 µg/mL) ACE inhibitory activity. Moreover, hydrolysate showed no cytotoxic activity on human and animal cell lines which makes it a very useful multifunctional method for peptide preparation. The compiled isolation procedure (ultrafiltration, size-exclusion chromatography and RP-HPLC) of bioactive peptides from YP hydrolysate resulted in obtaining peptides with the strong ACE inhibitory activity. One homogeneous and three heterogeneous peptide fractions were identified. The peptides were composed of 9-18 amino-acid residues, including mainly arginine and leucine at the N-terminal positions. To confirm the selected bioactive peptide sequences their analogs were chemically synthesized and tested. Peptide LAPSLPGKPKPD showed the strongest ACE inhibitory activity, with IC50 value of 1.97 µmol/L. BIOLOGICAL SIGNIFICANCE: Peptides with specific biological activity can be used in pharmaceutical, cosmetic or food industries. Because of their potential role as physiological modulators, as well as theirhigh safety profile, they can be used as natural pharmacological compounds or functional food ingredients. The development of biotechnological solutions to obtain peptides with desired biological activity is already in progress. Studies in this area are focused on using unconventional highly specific enzymes and more efficient methods developed to conduct food process technologies. Natural peptides have many advantages. They are mainly toxicologically safe, have wide spectra of therapeutic actions, exhibit less side effects compared to synthetic drugs and are more efficiently absorbed in the intestinal tract. The complexity of operation of large scale technologies and high cost of purification techniques are limiting factors to the commercialization of food-derived bioactive peptides. Research on the isolation of bioactive peptides in order to reduce the processing time and costs is continuously developing. Bioactive peptides can also be released from protein by-products of the food industry, which reduce the substrate expense and production cost as well as provide the added advantage of an efficient waste disposal. Moreover, proteins as precursors of food-derived peptides are well-tolerated by the human body and therefore their application in drug development may reduce costs and duration of toxicological studies during research, development and clinical trials.

Metal solubility enhancing peptides derived from barley protein.

Mineral supplements are required to be soluble as their bioavailability is highly correlated to their solubility in body fluids. In this study, metal binding capacity of barley protein hydrolysates and their purified fractions was investigated and expressed as increase in solubility of metal ions. Metal ions in the presence of hydrolysates exhibited a remarkable increase in solubility: 118, 32, 10, 29 and 35-fold for Fe(2+), Fe(3+), Ca(2+), Cu(2+) and Zn(2+), respectively. A mixture of low molecular weight peptides possesses a synergistic combination of both charged and hydrophobic residues and achieves the best binding metal ions. Electrostatic interactions via charged side chains and coordination binding with His and Cys, initially attract the metal ions and, afterward, hydrophobic interactions and aromatic ring stacking stabilize the positioning of metal ions in the structure of the peptide. Barley hordein hydrolysates show potential as dietary supplements that enhance both mineral solubility and bioavailability.

Biological and functional properties of proteolytic enzyme-modified egg protein by-products.

Enzymatic hydrolysis led to improve functional properties and biological activity of protein by-products, which can be further used as protein ingredients for food and feed applications. The effects of proteolytic enzyme modification of egg-yolk protein preparation (YP) and white protein preparation (WP), obtained as the by-products left during the course of lecithin, lysozyme, and cystatin isolation on their biological and functional properties, were evaluated by treating a commercial Neutrase. The antihypertensive and antioxidative properties of YP and WP hydrolysates were evaluated based on their angiotensin-converting enzyme (ACE)-inhibitory activity and radical scavenging (DPPH) capacity, ferric reducing power, and chelating of iron activity. The functionality of obtained hydrolysates was also determined. Neutrase caused a degree of hydrolysis (DH) of YP and WP by-products: 27.6% and 20.9%, respectively. In each of them, mixture of peptides with different molecular masses were also observed. YP hydrolysate showed high levels of antioxidant activity. The scavenging capacity, ferric reducing power, and chelating capacity were observed at the level: 0.44 µmol/L Trolox mg(-1), 177.35 µg Fe(2+) mg(-1), and 549.87 µg Fe(2+) mg(-1), respectively. YP hydrolysate also exhibited significant ACE-inhibitory activity, in which the level was 59.2 µg. Protein solubility was significantly improved as the DH increased. WP hydrolysate showed high water-holding capacity of 43.2. This study indicated that YP and WP hydrolysates could be used in foods as natural antioxidants and functionality enhancers.