Bioactive Peptides

There are numerous food processing methods. Food processing has both beneficial and negative impacts, from heating to eradicating microorganisms to adding substances to increase flavor. While it frequently causes nutrient loss, such as vitamin and mineral depletion, it may also boost the bioavailability of other nutrients. Protein is one of the nutrients that is favourably affected by the majority of the processing techniques that it goes through. By disrupting peptide connections, most techniques improve the availability of amino acids in proteins. A large number of chemical modifications happen when proteins are subjected to any form of processing (Udenigwe & Aluko 2012,p 1). Milk protein, being relatively simple, as it is composed of two types of proteins which are easily separated offers an avenue to study such changes. This paper outlines the effects of subjecting one milk protein, whey, to fermentation and the advantages and disadvantages of this exposure.

Whey Protein

Milk proteins are known for exerting a wide range of nutritional, biological and biological activities. Caesin and whey are the most common milk proteins as they possess properties that make them potential ingredients for preparing healthy meals (Bu et al 2010, p 2019). With casein being the most valued protein in milk, whey is often the by-product of most dairy industries, especially those producing cheese. However, recent studies have put the by-product on the list of essential components of milk. Whey protein is considered complete as it contains all the nine essential amino acids (Chemat & Khan, 2011, p 820). It has been related to many health benefits including possible therapeutic advantages. For example, Udenigwe & Aluko (2012, p 1) related the protein with loss of weight among overweight and obese individuals. It has also been said to have anti-cancer properties, improve immunity for children with asthma and prevent weight loss among people living with HIV, and lower blood cholesterol. Due to these advantages, whey protein has been extracted and sold commercially. Depending on the composition, there are three types of commercial whey proteins: whey protein concentrate, isolate, and hydrolysate. The Whey Protein Hydrolysate (WPH) is essentially used in supplements and infant formulas as it is considered predigested protein with improved digestibility and reduced potential to cause allergies (Udenigwe & Aluko, 2012, p 2).

However, the actual benefits of whey protein can be attained by breaking the peptide bonds the protein molecule to obtain the physiologically active peptides. This cleavage can be achieved through three methods: gastro-intestinal digestion of milk, hydrolysis by proteolytic enzymes and fermentation of milk using proteolytic culture (Hinrichs 2001, p 497). There is a large number of peptide sequences with specific bioactivity potential in whey protein. Studies have also determined the conditions for the release of these peptides resulting in technologies producing commercially viable peptides. Also, some of these peptides have been discovered in fermented milk products such as sour milk, yogurt, and cheese (Yamamoto, Ejiri and Mizuno, 2003, p 1350)

Deriving Bioactive Peptides by Fermentation of Whey

Bioactive Peptides are composed of covalently bonded amino acids. Although some biological peptides occur freely naturally, most of them are encrypted on parent protein by strong bonds that often need interventions to break. Microbial Fermentation is the most common method of breaking peptide bonds to obtain bioactive peptides in whey. The process involves a bacteria or yeast being cultured on protein substrates to hydrolyze the protein by the enzymes they produce when multiplied. As bacteria grow, they secret some proteolytic enzymes onto the whey which breaks the bonds and produces different types of proteins (Udenigwe & Aluko, 2012, p 1).

The process involves growing the chosen bacteria or yeast until its exponential phase in a broth is at optimal temperature. Then the bacteria cells are harvested, washed, and suspended in distilled water which should contain glucose and not be contaminated (Briczinski and Roberts 2002, p 3190). This solution will be used as the starter culture that is introduced into sterilized whey protein substrate. The extent of hydrolysis depends on time, and strain of bacteria used in the process. The differences in proteolytic systems among organisms account for the different level of hydrolysis. The substrate can be either milk or separated whey. However, the presence of other substances results in a low degree of hydrolysis. Bioactive peptides can also be obtained from yeast and filamentous fungi hydrolysis of proteins (Tavares et al., 2011, p 1015). To recover the supernatant, the mixture should be centrifuged then peptides obtained solvent extraction. Mass spectrometry can be used to determine the amino acid sequence of the peptides.

Importance of Bioactive peptides on Human Health

Whey-derived bioactive peptides have anti-diabetic properties and are considered useful for reducing blood sugar. Diabetes Mellitus is characterized by elevated blood sugar levels related to insufficient insulin production or poor reception to insulin by cells. Poor insulin secretion is related to type 1 diabetes while type 2 involves poor insulin reception by cells leading to elevated levels of both insulin and sugar in blood. Bioactive peptides are useful in the management of type 2 diabetes mellitus. They do this by inducing insulin-stimulated uptake of glucose in the 3T3-L1 cells (Tavares et al. 2011, p 1014). The increase in glucose uptake by cells leads to the decrease in glucose levels in the blood.

The second importance of whey-derived bioactive peptides is lowering the cholesterol. While cholesterol in the body has many roles including the synthesis of proteins, excessive amounts could result in the formation of plaques in blood vessels that often cause arteriosclerosis and other heart-related problems. For example, if the plaque forms in the coronary artery, it will reduce oxygen supply to the heart resulting in cardiovascular disease (Prazeres, Carvalho & Rivas, 2012, p 50). Other challenges related to elevated blood cholesterol include liver and kidney diseases. Whey derived peptides have been shown to prevent the initial cholesterol formation stages such as micelle formation and inhibit the lipase phase of cholesterol formation in the liver. Other bioactive peptides bid cholesterol forming compounds such as taurocholate and ursodeoxycholate in the gut thus preventing their absorption (Singh, Vij and Hati 2014, p 170)

Thirdly, bioactive peptides from whey are antihypertensive. The primary characteristic of hypertension is an elevated blood pressure of at least 140mmHg diastolic and 90mmHg systolic. The renin-angiotensin system is the most important in the physiological mechanism of hypertension. The peptides AQSAP, APLRV, AHKAL and IPAVF from whey protein are effective in inhibiting the angiotensin 1-converting enzyme which promotes hypertension (Tulipano, Sibilia, Caroli & Cocchi, 2011, p 835). Lactobacillus fermented whey also contains inhibitory effect on the angiotensin-inhibiting hormone.

Whey derived bioactive peptides also have an anti-cancer effect. The anti-oxidant peptides of whey protein cause oxidative changes that eliminate free radicals. The anti-oxidant properties of these peptides protect cellular oxidation of DNA, enzymes, proteins, membrane lipids and RNA. They scavenge free radicals in blood and eliminate them by oxidation (Tavares et al., 2011). Some also inhibit lipid pero-oxidation in presence and absence of enzymes. (Cozzolino et al 2003, p 290)

Bioactive peptides also show some direct antimicrobial activity by acting on different types of bacteria, viruses, and yeast. Most of the antimicrobial peptides also show other properties such as immunomodulation, wound healing, and antioxidant. The use of bioactive peptides is alternative to resistance inducing antibiotics. The microbial fighting peptides have a varying length varying from twelve to fifty amino acids. Anti-microbial peptides are characterized by the presence of positive charge or having both hydrophobic and hydrophilic at the terminals (Tulipano et al., 2011, p 834). These are the points of interaction with microbes. These biopeptides may kill bacteria by making pores in its walls or interacting the macromolecules inside the bacteria (Saito 2008, p 300)

Whey-derived biopeptides also have immunomodulatory characteristics. Some of the peptides in resulting from fermentation of whey have shown phagocytic characteristic on some bacteria. The peptides have also been reported to cause the stimulation of immune competent cells, proliferation, and stimulation of lymphocytes and macrophages. Others stimulate the synthesis of antibodies and regulation of cytokine (Pihlanto 2000, p 349). The Glycomacropeptide (GMP) together with its derivatives has essential immunomodulatory functions like suppressing the effects of IgG antibodies. Other peptides are used in the immune therapy of HIV-infected patients. They promote the growth of infection inhibiting enteric bacteria in the gut such as lactobacilli and bifidobacteria. They are, hence, primarily importance in the maintenance of mucosal integrity to prevent the entry of disease-causing micro-organisms. There are also opioid peptides that are derived from the milk whey protein which interacts with the nervous system. These peptides interact with the ligands of the nervous system and cause behavior changes, appetite, and hypotension. They regulate the growth of nerves and the endocrine system as a whole. (Korhonen, 2009, p 180).

Generally, there is a general preference for biopeptides with a wide range of activities. However, only a small number of wide range biopeptides have been documented. Most of the documented peptides have a single function within the body of human beings. The challenge to achieving great heights with bioactive peptides lies in the ability to separate them according to amino acid content. There is a large number of ways in which protein can break into peptides when subjected to proteases. Studies are needed to identify more peptides and their importance in the human body (Madureira et al 2010, p 450).

Conclusion

Exposing milk and its products to processing results not only in an increase in the bioavailability of protein but also confers other benefits that could not be achieved if taken raw. In this case, we take the fermentation of whey protein from milk to understand the health implication. Fermentation using either bacteria or yeast results in the breaking of peptide bonds of long protein molecules to produce small chains of amino acids called peptides. Other methods are present for achieving this hydrolysis such as the direct introduction of the proteolytic enzymes into the substrate. The resulting peptides have many health benefits which could not be obtained by other methods of processing the substrate. The resulting peptides have certain properties such as opioid, antimicrobial, immunomodulation, anti-oxidation and anti-hypertensive properties. This study not only shows the importance of protein fermentation but the processing of most foods. The findings from this work can be exploited to make special health claims aimed at improving the treatment of certain diseases such as hypertension, diabetes and HIV/AIDs among others.

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