The Nuffic Glossary is a list with explanations of terms used in Dutch education.
The professor who officially supervises the work of a student who is pursuing a doctorate. The work of the supervisor may be delegated to another member of staff, known as the co-promotor. This term should never be translated as 'promoter'.
In English a 'promoter' is most likely to be promoting either a cause or a sporting event. Please note that the word promotor is more specific than the word 'supervisor' or even 'thesis supervisor'. The level of PhD is implicit in the Dutch term so that unless the context makes this clear, you might need to add some explanation to the term 'supervisor'.