If you want to remove white space after you get the excerpt, then you can do as below.
First get the excerpt as
$excerpt = mb_substr(get_the_excerpt(), 0, 236);
Then do a string replace for space as
echo str_replace(' ', '', $excerpt);
If you want to remove white space after you get the excerpt, then you can do as below.
First get the excerpt as
$excerpt = mb_substr(get_the_excerpt(), 0, 236);
Then do a string replace for space as
echo str_replace(' ', '', $excerpt);