The dye-linked formaldehyde dehydrogenase (dlFalDH) from Hyphomicrobium zavarzinii ZV 580 processes formaldehyde in a highly selective manner and without need for NAD(P). The enzyme thus has considerable potential for technical applications if the difficulties associated with its efficient production can be resolved. In this contribution, a fed-batch bioprocess is developed, which improves both the biomass production of H. zavarzinii ZV 580 (from 0.6 to 2 g 1(-1) dry mass) and the specific dlFalDH production ( from 0.1 to 0.3 units g(-1) biomass), resulting in an overall improvement of the productivity by more than an order of magnitude compared to the previously reported process ( Klein et al., Biochem J 301: 289-295, 1994). In particular, the process uses an automated feeding strategy controlled via the dissolved oxygen concentration. In addition, our results show that the growth of H. zavarzinii ZV 580 is rather sensitive toward increasing salt concentration in the culture medium. Growth is also inhibited by the presence of surfactant-based antifoam reagents. Adjustment of the pH via the addition of methylamine instead of NaOH, on the other hand, leads to an increase in biomass yield.