How to Replace a word

[Klaus Gebhardt]

I need a MySQL-statement to replace a specified word in a column.
Example: One record holds the sentence
"An auditor drives an audi."

The statement should replace the audi at the end of the sentence but not the auditor.
My current workaround is that I replace words only when surrounded by spaces, but this does not work in the above sentence, obviously.

I am familiar with the RLIKE/REGEXP statement and it works good for showing records with words, which needs to be replaced.
But I have no clue, how to combine both.

If there is no easy way, maybe somebody has already solved the problem with a PHP-procedure?
Thanks
Klaus