How to disable the workflow notifications that are sent out on PO approval

Hi

on 12.1.3

I have two questions:

1) Upon PO being approved, who receives workflow notifications?

If there is a note id that lists the PO based notifications and the recipients, it would be of great help.

2) When the PO gets approved, the user gets notification 'Standard Purchase Order 10117xxxxxx has been approved'.

How can we disable these notifications as the business user does not want to receive them.

Your inputs are greatly appreciate

Thanks in advance