This little module adds settings to the taxonomy autocomplete. You can configure an autocomplete widget for a vocabulary to set its autocompletion by matching anything in the searched string or by matching the beginning of a searched string.
http://drupal.org/project/taxonomy_autocomplete_settings [2]
Links[1] https://dominiquedecooman.com/contribtion/taxonomy-autocomplete-settings [2] http://drupal.org/project/taxonomy_autocomplete_settings