"Aginomoto" or "Ajinomoto" is actually the brand name of a Japanese company that primarily produces monosodium glutamate (MSG).
In summary, Ajinomoto, in 2001, had a legal ban in Indonesia because it was found that the Indonesian plant was using a porcine-based (pork-based) extract to culture enzymes used to produce its MSG. To my understanding and research, the situation only affected Indonesia, given the plant was not for export purposes. As such, all other internationally available Ajinomoto MSG is definitely plant-based, and would be permissible. Please do note that Ajinomoto MSG is not only used in Chinese food, but also in Indian, Mexican, Japanese and may other cuisines.
The legal issue that arose in Indonesia is because Aginomoto used pork-based extracts to create its enzyme culture, as opposed to its usual process of using plant-based extracts.
An important distinction needs to be made, at least for the purposes of technical clarity (although ethically and practically, this is not necessarily the most palatable possibility for most Muslims...). The process that Ajinomoto uses to manufacture MSG is technically Halal and acceptable within Islam. The process of creating enzymes leads to the original extracts (almost always plant-based) to be completely altered in its molecular form, and based on the principle of Istis-haab, because the final product is also non-reversible to the original extracts and that there is no trace of the original extract, then the final product is definitely Halal. As a quick example of its Halal status, Malaysia's Board for Halal Certification accepts the MSG as Halal.
A more important issue surrounding MSG is its health consequences, and a more important Islamic concern. MSG is known to cause brain as well as digestive problems, although the political nature of such matters have led the issue to be non-conclusive. Having said that, plenty of information and data exists that confirm its harmful effects. Most countries require that MSG be listed (E620-E625).
Finally, I suggest that you contact your local Halal certifier as well as Aginomoto distributor and find out what the local ingredients may be in its production if it is produced locally. If it is produced off-shore, find out which country it is manufactured in and follow up on their process.