How to sort posts in a custom post type by title in ascending order by default?

You should use pre_get_posts:

add_action('pre_get_posts','wpse56753_businesses_default_order');
function wpse56753_businesses_default_order( $query ){
    if( 'business' == $query->get('post_type') ){
        if( $query->get('orderby') == '' )
            $query->set('orderby','title');

        if( $query->get('order') == '' )
            $query->set('order','ASC');
    }
}