In symbiotic processes, different organisms coexist stably and interact by sharing the same metabolites and environmental conditions. The robustness of a symbiotic nisin production process system composed of the lactic acid bacterium Lactococcus lactis subsp. lactis (ATCC11454) and dairy yeast Kluyveromyces marxianus (MS1) was studied. It was found that this symbiotic process system was robust to the initial disturbance in the inoculum sizes of both microorganisms and pH.