This study presents the fermentative production of the platform chemical itaconic acid using the fungus Ustilago maydis. The innovative aspect here is that the fermentation is run continuously with integrated cell retention and product recovery using membranes. Unlike conventional membrane processes, we use the recently introduced "reverse-flow diafiltration" which prevents performance loss by periodically reversing the flow direction. Results show that filtration stability can be (1) significantly improved compared to conventional membrane processes and (2) product recovery was constantly high at highly dynamic conditions. This is especially remarkable when taking into account the complex nature of fungi cells which tend to block surfaces rapidly. (C) 2013 Elsevier Ltd. All rights reserved.