In our project ToPiS – Towards Pilot Scale Production of Natural Products with Filamentous Defined Co-cultures within the DFG priority program 2170 “InterZell”, we investigate factors for a successful establishment of microbial co-cultures for biotechnological productions. Consolidated bioprocessing (CPB) with synthetic microbial co-cultures holds great promise for the utilization of difficult substrates or the production of new biomolecules. However, combining different microorganisms, increases the biological and process complexity tremendously and novel methods of bioprocess monitoring and process steering are required. In this work, we investigate the use of a cellulolytic fungus, T. reesei, with a model producer of natural products, S. coelicolor A3(2), for CBP starting from cellulose. The goal is to set standards for process monitoring and control that can then be translated to different microbial co-culture bioprocesses.