Disturbances during operation are an ubiquitous feature of large-scale fermentations. This kind of process noise is often describable by a Gaussian distribution and is considered undesirable but unavoidable. In this paper, the fed-batch production of streptokinase (SK) was studied when such disturbances occurred in the inflow rate of the substrate. As the Variance of the noise increased upto 6% of the instantaneous Value of the flowrate, there was a gradual improvement in the SK activity, after which the activity decreased for larger variances. The peak activity (10 850 U/ml) was 22% higher than for a smooth noise-free feed. Similar earlier observations for beta-galactosidase and beta-lactamase suggest that normal disturbances may be harnessed to enhance fermentation efficiency by filtering them such that they are maintained within an optimal range.