Expandex® is an American product - a lot of consumers like to know where there food originates. It emphasizes that fact that it is totally gluten-free in the US market-place:
http://expandexglutenfree.com/index.php
Previously, some yeast were grown on dried malt extract [not gluten-free] - but it is mostly corn-based these days .. Home brewer still used DME to cultivate their yeasts ...