In this paper, a system of cell-recycle continuous fermentation for sodium gluconate (SG) production by Aspergillus niger (A. niger) was established. Based on initial continuous fermentation result (100.0 h) with constant feed rate, an automatic feedback strategy to regulate feed rate using on-line physiological parameters (OUR and DO) was proposed and applied successfully for the first time in the improved continuous fermentation (240.5 h). Due to less auxiliary time, highest SG production rate (31.05 +/- 0.29 g L-1 h(-1)) and highest yield (0.984 +/- 0.067 mol mol(-1)), overall SG production capacity (975.8 +/- 5.8 g h(-1)) in 50-L fermentor of improved continuous fermentation increased more than 300.0% compared to that of batch fermentation. Improvement of mass transfer and dispersed mycelia morphology were the two major reasons responsible for the high SG production rate. This system had been successfully applied to industrial fermentation and SG production was greatly improved. (C) 2016 Elsevier Ltd. All rights reserved.