Wm. Wrigley Jr. Company won US patent 6194008 27 February for ‘Environmentally friendly chewing gum bases including polyhydroxyalkanoates.’ The main claim is first use of polyhydroxyalkanoates, and any challenge can be mounted only if prior use of this group of chemicals can be proved as base of chewing gum.
Besides Wrigley, the only other player in this field is Rijksuniversiteit te Groningen, and, earlier, International Flavors & Fragrances, who pioneered the flavouring use of alkanoate (monomer) for chewing gums, but coincidentally, did not propose it as base for chewing gums.
Abstract:
Chewing gum bases, and resultant chewing gums, that are environmentally friendly are provided. The chewing gum base comprising approximately 1 to about 99% by weight polyhydroxyalkanoates having side chain lengths of C4 to C30.
First of 20 Claims:

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By GlobalDataA chewing gum base including polyhydroxyalkanoates having side chain lengths of C4 to C30.
By Navroz Havewala, just-food.com correspondent