Why is it difficult to grow anaerobes in vitro?

Anaerobes are not able to have growth in the presence of much of oxygen environment as they do not have catalse. Catalse is the enzyme for clearance of oxygen. There are also anaerobes protects their own self from oxygen by production of an enzyme known as super oxide dismutase. Therefore, it is not easy task for creation an oxygen-absent environment for anaerobes in the vitro so they cannot be grown in vitro.