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Use of microbial transglutaminase to reduce egg protein allergenicity

Final Report Summary - EGGALL (Use of microbial transglutaminase to reduce egg protein allergenicity)

The project aimed to investigate whether microbial transglutaminase (mTG) mediated modification could be used to reduce the immunogenic properties of the proteins ovomucoid and ovalbumin present in egg white.

The structural stability of the proteins to thermal processing and in vitro digestion was investigated before and after enzymatic modification with mTG. Using a multidisciplinary approach, we developed strategies for enzymatically modifying the major egg allergens ovalbumin and ovomucoid with mTG to reduce the immunoreactivity of these proteins. Introducing this enzyme for modifying egg white proteins will enable the rational development of healthier foods with improved functionality that can also combat the deleterious health effects resulting from the current allergy crisis in the EU. At the host institution (IFR) Concetta Valeria L. Giosafatto has, in particular, carried out experiments using in vitro digestion under physiologically relevant conditions following established IFR protocols. Both mTG-modified samples and the corresponding controls, treated in the absence of the enzyme, were submitted to in vitro digestion. Simulated gastric-followed by duodenal digestion was performed with / without the physiological surfactant phosphatidylcholine (PC). The results demonstrate feasible approaches for modifying the proteins by means of the crosslinking enzyme to control (reduce) the rate of proteolysis and hence potentially induce physiological responses that could moderate food consumption.

The project initially looked at the modification of the egg white proteins, ovalbumin and ovomucoid, by means of the enzyme mTG. Before the enzymatic modification, the proteins were firstly purified and their secondary structure characterised by means of Circular Dichroism (CD) and Infrared Spectroscopy (FTIR). These studies were then extended to investigate the effects of the enzymatic modification on digestion carried out under both gastric and duodenal conditions and on rheological properties.

EGGALL has made use of rheological tools to investigate the effect of mTG on the viscoelastic properties of egg protein gels. Secondly simulated digestion experiments under gastric and duodenal conditions were carried out on unmodified and mTG-modified samples that had undergone a range of processing conditions. Furthermore, by using an enzymatic approach, based on the enzyme Peptide-N4-(acetyl-b-glucosaminyl) asparagines amidase (PNGase F), Dr Giosafatto was able to fully deglycosylate the ovomucoid protein. The important finding of a synergism between sulfhydryl reagent, surfactants and heating suggests that similar approaches could also be applied for the deglycosylation different glycoproteins, in which the glycans are responsible of their immunological properties. This is generating renewed scientific interest due to the growing social and economic consequences of the allergy crisis in the developed world. The design of healthier foods to control the allergy is a top priority in the EU: it is estimated that treating allergy and related conditions takes up to 7 % of the total healthcare budget within the EU. EGGALL has shown through the application of fundamental science that an enzymatic approach, based on the enzyme mTG can change the digestibility and rheological properties of proteins.