Fed-batch production of a bioflocculant from Corynebacterium glutamicum.

The constant-rate fed-batch production of the polygalacturonic acid bioflocculant REA-11 was studied. A controlled sucrose-feeding strategy resulted in a slight improvement in biomass and a 7% reduction in flocculating activity compared with the batch process. When fed with a 3 g l(-1) urea solution, the flocculating activity was enhanced to 720 U ml(-1) in 36 h. High cell density (2.12 g l(-1)) and flocculating activity (820 U ml(-1)) were obtained in a 10-l fermentor by feeding with a sucrose-urea solution, with values of nearly two times and 50% higher than those of the batch process, respectively. Moreover, the residual sucrose declined to 2.4 g l(-1), and residual urea decreased to 0.03 g l(-1). Even higher flocculating activity of 920 U ml(-1) and biomass of 3.26 g l(-1) were obtained by feeding with a sucrose-urea solution in a pilot scale fermentation process, indicating the potential industrial utility of this constant-rate feeding strategy in bioflocculant production by Corynebacterium glutamicum.