Japanese seasonings company Ajinomoto has been hit with a lawsuit demanding it pay ¥2bn (US$16.4m) to a former employee.

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Masayoshi Naruse, the former head of one of Ajinomoto’s research institutes, claims the company has withheld payment for his transferral of the rights to the patents for aspartame, now sold by Ajinomoto under the PalSweet brand. Sources close to the situation claim that the fair amount of compensation for the transfer of rights had been legally guaranteed.


Naruse developed the sweetener, which has become a flagship product for Ajinomoto, in 1982. Some 200 times sweeter than sugar, aspartame contains almost no calories and has become a key ingredient for food and drinks for diabetics, as well as in diet CSDs (carbonated soft drinks).


Under Japanese patent law, company employees who invent products as part of their professional tasks are entitled to secure patents for the inventions in their own name and then gain a “fair payment” when they pass the rights to the patent on to their company.


Ajinomoto has earned around ¥27.9.bn from selling licensing fees to aspartame, primarily to US companies. Naruse was paid ¥10m as a reward for his invention. Given that discrepancy between these two figures, Naruse’s legal team feels its case is strong.

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Ajinomoto has reason to be concerned that Naruse’s suit, if successful, could prompt a chain of similar suits, as the company holds many other patents related to amino acid application technologies.

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