2 Protein Source and Research of Bioactive Peptides
The production of bioactive peptides currently in the market starts with the choice
of a protein source followed by hydrolysis with the release of bioactive peptides
from the primary sequence of the native proteins. The main precursors of bioactive
peptides are mainly proteins of animal origin such as meat, milk (casein and serum
proteins), eggs, although proteins from plant sources are also in use, such as soybean proteins, wheat, rice, and others [3]. Recently, considerably more attention has
also been devoted to research and testing of new sources of proteins such as fish
residues, sponges, algae, and mollusks. Ishak and Sarbon [4] tested the production
of bioactive peptides by hydrolysis of shortfin scad (Decapterus macrosoma) waste
residues with endogenous proteases and addition of Alcalase. Another possible
source of these peptides is the design and biosynthesis by recombinant host
microorganisms. The most recent studies in this field include the expression of a
specific sequence of a peptide by algae in recombinant proteins, being the bioactive
peptide released after protein digestion [5]. However, hydrolysis of caseins and
whey proteins are the primary sources and references for the discovery of bioactive
peptides after the screening of their biological activity [6].
Milk consists of two heterogeneous families of proteins, one insoluble composed
of caseins (80% w/w) and the other containing soluble proteins such as serum
proteins (20% w/w). Caseins in the milk are organized in micelles and are composed of four caseins: a s1 (40%), a s2 (10%), b (36%), and k (14%). Whey proteins
are a sub-product of cheese making. Whey proteins are constituted mainly by serum
proteins, rich in human-essential amino acids, in particular of amino acids with
branched side chains, and containing amino acids with sulfur residues [7]. The
protein profile of whey proteins includes b-lactoglobulin (b-LG, for short),
a-lactoalbumin (a-LA), immunoglobulins (IG), bovine serum albumin (BSA),
bovine lactoferrin (BLF), lactoperoxidase (LP), and glycomacropeptides
(GMP) [8].
The whey protein concentrate (WPC) is obtained by ultrafiltration (UF) from
acid or sweet whey proteins. The pH of acid whey is equal to or less than 5.1,
resulting from the addition of an acidic agent to milk, while the pH of sweet whey is
equal to or greater than 5.6 obtained after enzymatic coagulation of milk. On the
other hand, nowadays, whey protein isolate (WPI) is also available and produced by
eliminating fat, cholesterol, carbohydrates, in particular lactose, using UF. Additionally, pure whey proteins such as b-LG, a-LA, BLF, and BSA are already
produced at a large-scale and available in the industrial market [7]. The whey
proteins and hydrolysates, and their fractionated peptides released from the protein
parent molecules, together with other smaller whey components, were identified as
responsible for a wide variety of nutritional and physiological effects [9]. These
effects include among others (i) physical performance, recovery after exercise and
prevention of muscle atrophy; (ii) satiety and weight control; (iii) cardiovascular
health; (iv) anticancer activity; (v) wound treatment and recovery; (vi) infection
control; (vii) child nutrition and (viii) healthy aging [10].
Enzymatic Production of Bioactive Peptides from Whey Proteins …
475
The production of bioactive peptides currently in the market starts with the choice
of a protein source followed by hydrolysis with the release of bioactive peptides
from the primary sequence of the native proteins. The main precursors of bioactive
peptides are mainly proteins of animal origin such as meat, milk (casein and serum
proteins), eggs, although proteins from plant sources are also in use, such as soybean proteins, wheat, rice, and others [3]. Recently, considerably more attention has
also been devoted to research and testing of new sources of proteins such as fish
residues, sponges, algae, and mollusks. Ishak and Sarbon [4] tested the production
of bioactive peptides by hydrolysis of shortfin scad (Decapterus macrosoma) waste
residues with endogenous proteases and addition of Alcalase. Another possible
source of these peptides is the design and biosynthesis by recombinant host
microorganisms. The most recent studies in this field include the expression of a
specific sequence of a peptide by algae in recombinant proteins, being the bioactive
peptide released after protein digestion [5]. However, hydrolysis of caseins and
whey proteins are the primary sources and references for the discovery of bioactive
peptides after the screening of their biological activity [6].
Milk consists of two heterogeneous families of proteins, one insoluble composed
of caseins (80% w/w) and the other containing soluble proteins such as serum
proteins (20% w/w). Caseins in the milk are organized in micelles and are composed of four caseins: a s1 (40%), a s2 (10%), b (36%), and k (14%). Whey proteins
are a sub-product of cheese making. Whey proteins are constituted mainly by serum
proteins, rich in human-essential amino acids, in particular of amino acids with
branched side chains, and containing amino acids with sulfur residues [7]. The
protein profile of whey proteins includes b-lactoglobulin (b-LG, for short),
a-lactoalbumin (a-LA), immunoglobulins (IG), bovine serum albumin (BSA),
bovine lactoferrin (BLF), lactoperoxidase (LP), and glycomacropeptides
(GMP) [8].
The whey protein concentrate (WPC) is obtained by ultrafiltration (UF) from
acid or sweet whey proteins. The pH of acid whey is equal to or less than 5.1,
resulting from the addition of an acidic agent to milk, while the pH of sweet whey is
equal to or greater than 5.6 obtained after enzymatic coagulation of milk. On the
other hand, nowadays, whey protein isolate (WPI) is also available and produced by
eliminating fat, cholesterol, carbohydrates, in particular lactose, using UF. Additionally, pure whey proteins such as b-LG, a-LA, BLF, and BSA are already
produced at a large-scale and available in the industrial market [7]. The whey
proteins and hydrolysates, and their fractionated peptides released from the protein
parent molecules, together with other smaller whey components, were identified as
responsible for a wide variety of nutritional and physiological effects [9]. These
effects include among others (i) physical performance, recovery after exercise and
prevention of muscle atrophy; (ii) satiety and weight control; (iii) cardiovascular
health; (iv) anticancer activity; (v) wound treatment and recovery; (vi) infection
control; (vii) child nutrition and (viii) healthy aging [10].
Enzymatic Production of Bioactive Peptides from Whey Proteins …
475