In parallel to his activities as scientific assistant at the Ludwig-Maximilians-University and at the European Nuclear Research Centre CERN in Geneva from 1991 to 1997, he also gained a PhD in social sciences.

Castulus gathered experience in consulting and applied research with on of the leading top management consulting firms and the Institute for Innovation Research of the German Fraunhofer Society before he was appointed as a director to the management board of a business consulting subsidiary of the latter in 2000.
In 2001, he changed to the management of the holding company for businesses in the field of new media of a large German publishing house.

There, Castulus was responsible for the corporate venture management and, as business development manager, for the setting-up of new businesses and innovations at the interface print-online.

Since the beginning of 2004, Castulus is working as a freelance business consultant. He has extensive project experience in the fields of (new) media, publishing, telecommunication, technology and innovation.

In addition to his consulting and management duties, Castulus continued his academic activities as a lecturer at several universities on innovation management, media and ICT (among others in Munich and St. Gallen). His research is published in various international journals.