The chebi.owl available here ftp://ftp.ebi.ac.uk/pub/databases/chebi/ontology/
is potentially confusing to users. It uses an annotation vocabulary that is non-standard and unique to CHEBI.
I recommend you use the standard OWLAPI obo<->owl translation. You can use the latest version of Protege, or a command line tool such as
If you do this we can also simplify the OBO central build pipeline (at the moment we are forced to make our own CHEBI build using this jenkins job - http://build.berkeleybop.org/job/build-chebi/ )