Subsequent improvement of lactic acid production from beet molasses by Enterococcus hirae ds10 using different fermentation strategies

Abstract

Different fermentation strategies were investigated for improving lactic acid (LA) production by homofermentative LA-producing strain, Enterococcus hirae ds10. Batch mode with initial sugar molasses of 69.53 g/L achieved LA production of 36.79 g/L with a yield of 0.91 g/g and productivity of 1.02 g/L/h; however, 52% of sugar molasses was only consumed. Otherwise, in batch mode with high cell density (HCD), strain ds10 consumed more substrate achieving LA production at 49.49 g/L at yield (0.91 g/g) and low LA productivity (0.41 g/L/h). Subsequently, one-pulse and multi-pulse fed-batch strategies with/without HCD were provided better sugar utilization and higher LA production but low LA productivity was obtained. Interestingly, the repeated batch fermentation was conducted for 16 runs and achieved the highest LA of 61.76 g/L after 30 h at a higher initial sugar concentration of 85.87 g/L with an improvement of LA productivity at 2.06 g/L/h and yield at 0. 97 g/g.