bbPress.org

so, with some help from a collegue, this is how to do it:

update wp_users  
    set wp_users.user_email = "myemail@email.com"
    where
    wp_users.ID IN (
    select  
    wp_usermeta.user_id
    from wp_usermeta
    where (wp_usermeta.meta_key = "wp_capabilities") &&  (wp_usermeta.meta_value like 
    "%bbp_participant%")   
    )
    ;