Membrane bioreactor systems can efficiently reduce product inhibition in lactic acid production processes, enhancing their productivity. Filtration parameters, e.g. crossflow velocity and transmembrane pressure, were controlled with varying biomass concentration, which was monitored using an optical sensor in real time. The filtration flux was successfully maintained as desired according to the control strategy. We also investigated the effect of feed concentration and dilution rate on process characteristics. The continuous fermentation remained stable for more than 80 h, achieving the highest productivity of 8.6 gL(-1)h(-1) with a feed concentration of 70 gL(-1) and a dilution rate of 0.2 h(-1).