
Two ways you could do this...
(1) Remove the .uk-container and .uk-container-center classes by adding this in functions.php:
add_action( 'beans_uikit_enqueue_scripts', 'my_theme_enqueue_uikit_assets' );
beans_add_smart_action( 'wp', 'my_theme_enqueue_uikit_assets' );
function my_theme_enqueue_uikit_assets() {
beans_remove_attribute( 'beans_fixed_wrap[_main]', 'class', 'uk-container uk-container-center' );
}
(2) Overwrite the .uk-container class, as explained here: http://www.getbeans.io/documentation/overwriting-or-extending-uikit-components/.

Hello,
Kevin : you can add
beans_remove_attribute( 'beans_fixed_wrap[_main]', 'class', 'uk-container uk-container-center' );
directly in your functions.php, can't you ? No need to enqueue this in
beans_uikit_enqueue_scripts
Mat

Ah, you're right. Sorry, that's just me trying to think while on autopilot.
If you want to use an action hook, it would be wp
. I've changed my previous post to reflect this. But as you said, beans_remove_attribute
will do just fine sitting in functions.php on its own.