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Isolation and identification of egg white proteins using biochemical techniques

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  1. Introduction
  2. Objectives
  3. Results
  4. Discussion
  5. Conclusion

Human beings need a balanced diet of carbohydrates, proteins, fats and numerous other nutrients. Proteins are needed as part of a healthy balanced diet in order to sustain growth, provide structural support, boost the defences of the body and are involved in many vital body functions. Among the various sources of protein, one commonly consumed, rich source of such proteins is the eggs of the domestic fowl.

The eggs of the domestic fowl consist of the egg white (albumen) and egg yolk. Egg albumen, which is the focus of this experiment, is a mixture composed of 88% water, 10% of different proteins and 2% of small quantities of carbohydrates, minerals and vitamins. Further focusing on the different kinds of proteins in egg white, the protein ovalbumin comprises of 54% of the protein percentage, and conalbumin consists of 12 % and ovomucoid, 11% and ovomucin, 3.5% and lysozyme, 3.5% and ovoglobulin, 8% and the rest of the 8% of various proteins. These proteins provide some biological benefits to the egg and to its consumers, which is why separating and studying these proteins and their special biochemical characteristics is very important.

Ovalbumin protein has the largest composition in the egg white and is known to be the most nutritive part of the egg. Evidences have shown that it provides protection for the egg and acts as a calcium binder and also chelates to heavy metals trapping the metal ions within its sulfhydryl bonds. The protein conalbumin helps in retarding the growth of microorganisms by chelating the protein that binds iron and other minerals into a stable complex and hence produces a deficiency of minerals for the invading microorganisms. The tyrosine and histidine amino acid residues are involved in this metal binding. Ovomucoid protein acts as a proteinase inhibitor and so it inhibits bovine or trypsin enzyme activity and hence it inhibits growth of bacteria. It is also responsible for the gel structure of egg white. The protein ovomucin inhibits viral hem-agglutination, while lysozymes contain enzymes such as N-acetylmuramidase, which is involved in the hydrolysis of the cell wall of Gram positive bacteria and hence, also contributes to anti-microbial activity (Ahlborn & Sheldon, 2006; Belitz, Grosch & Schieberle, 2009; Gettins, 2002).

[...] Furthermore, the calculations show that the iron binding capacity of conalbumin is very high as 1 mole of conalbumin binds to 2.635 moles of iron which is a large amount of iron that conalbumin binds to. CONCLUSION Ovalbumin was found to have the highest amount of protein as compared to lysozyme and conalbumin. The specific activity and total activity showed that lysozyme D was the most effective enzyme to catalyse reactions of reducing bacterial activity and then lysozyme A and then lysozyme C and lastly lysozyme B. Moreover, the iron binding capacity of conalbumin was studied and it was found that 2.635 moles of iron was required to bind to 1 mole of conalbumin. [...]

[...] 548- 550. Dennison, C Chapter: Assay, extraction and sub-cellular fractionation, In A Guide to Protein Isolation, 2nd edn., Kluwer Academic Publishers, Dordrecht, Netherlands, p Gettins, P.G.W ?Serpin structure, mechanism, and function', Chemical Reviews, vol no pp. 4751-4804, viewed 23 May 2011, Chaudhuri, J.B. & Spirovska, G ?Recovery of proteins from reversed micelles using a novel ion-exchange material'. Biotechnology techniques Springer journals, vol no pp. 909-914, viewed 23 May 2011, [...]

[...] RESULTS Week 1 Initial volume of egg white = 57 ml, Remaining volume of egg white = 56 ml. Volume of dissolved ovalbumin = 33 ml Volume of conalbumin supernatant = 84 ml Calculation of the mass of ammonium sulphate required to produce an solution of conalbumin supernatant mixture. ( ) x 100 = = = = 6.72 g Table Final volume of conalbumin and ovalbumin after dialysis Week 2 Part A results Volume of egg white used = 25 ml Table Volume of lysozyme supernatant solutions obtained after centrifuging. [...]

[...] Table Absorbance readings at 570 nm for and the mass of the proteins in each of the different dilutions of conalbumin, ovalbumin, lysozyme C and D and egg white protein samples in 1ml of final solution. Calculation of the mass of protein in each protein sample of different dilutions Using the equation obtained from the BSA standard curve (Figure y = 0.0519 x The equation means: Absorbance = 0.0519 x mass of protein in each protein sample Therefore: m = Absorbance / 0.0519 Example calculation 1 for undiluted conalbumin: m = 1.198 / 0.0519 Mass of protein in undiluted conalbumin sample = 23.1 mg Example calculation 2 for 1/10 dilution of conalbumin: m = 0.196 / 0.0519 Mass of protein in 1/10 dilution of conalbumin sample = 3.78 mg Likewise, the rest of the masses of the protein in each protein sample at different dilutions was calculated using the equation of the line from the BSA standard curve (Figure and recorded in Table 4. [...]

[...] Bibliography Ahlborn, G. J. & Sheldon, B. W ?Identifying the components in eggshell membranes responsible for reducing the heat resistance of bacterial pathogens', Journal of food protection, vol no pp. 729- 738, viewed 23 May 2011, Belitz, H.D., Grosch, W. & Schieberle, P Chapter: Eggs, In Food Chemistry, 4th edn., Springer-Verlag Berlin, Heidelberg, Germany, pp. [...]

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