They had a guest who insisted that a particular cheese could not be suitable for a vegetarian, whereas a member of staff at Le Manoir was under the impression that it was. Le Manoir was at fault as animal rennet is used to make many types of cheese and for that guest that constituted an animal food which he could not eat.
Le Manoir now set about sourcing cheese that was suitable for vegetarian use and came across a dilemma. Rennet is now produced by several organisms including Aspergillus niger that have had the gene for rennet introduced into them by genetic manipulation.
Quite apart from the debate of whether or not we should be eating GM food and whether or not those foods are appropriate in a high class restaurant that insists on the finest sourced ingredients, this means that we can now have rennet - in some ways an animal protein - produced by micro-organisms that are certainly not animal in origin.
Should a vegetarian accept these proteins as non-animal? They have never been near an animal but the DNA sequence originates in an animal. Perhaps individuals should be able to make that choice themselves? - but here there is a second point. Food that has been produced using a GM product does not have to be labelled GM, so no-one, restaurateur, customer or consumer knows that they are there and thus cannot make that decision for themselves.
There are now many more examples of foods or food constituents being made using Aspergillus. There is some evidence that foods can cause allergic reactions, even in parts of the body remote from the digestive system - in fact there are examples of a food made from a fungus (Quorn) that can cause repiratory problems and include cross reactivity to Aspergillus. This raises the possibility that such foods could adversly effect the allergies of patients suffering from a wide range of allergies, including allergy to Aspergillus e.g. ABPA, sinusitis.
If some foods can contain Aspergillus or other microorganism without our knowledge then perhaps the labeling regulations need to be rethought-out.