Is organic vegetarian cheese non GM?
Rennet (the main constituent of which is the enzyme chymosin) traditionally comes from calves stomachs, which made the cheeses unacceptable to vegetarians. In 1987 'vegetarian rennet' became available. This was produced by introduction of the gene for chymosin production from pigs into yeast (i.e genetic modification). The yeast is then grown in a liquid sugar material and excretes the chymosin into the liquid. The chymosin is then extracted from the liquid, and purified, so there is no yeast present. The majority of vegetarian rennet contains chymosin produced by this process; so most vegetarian cheese is produced with this rennet (as is most non vegetarian cheese as this chymosin is cheaper than calf rennet).
More recently enzymes similar to chymosin have been found in some bacteria and fungi which have not been genetically modified. These enzymes are now produced by a similar fermentation and purification process from these bacteria or fungi and are used to make 'non GM vegetarian rennet'.
All organic products must not use GM organisms or their derivatives. This includes enzymes which must be from non GM organisms. To ensure that this is the case every cheese manufacturer must submit a GM declaration from their 'rennet' supplier that the material is not derived from a GM organism. There could be some organic cheese makers who are using calf rennet. The calves would not need to be organic as the enzymes are permitted processing aids so don't have to be organic. Clearly in that case the cheese could not be suitable for vegetarians.
Read the Vegetarian Society website where they have more information about GM rennet. In general they do not allow GM but they appear to make an exception for the chymosin from GM yeast.