Effect of CO partial pressure on cell-recycled continuous CO fermentation by Eubacterium limosum KIST612

Eubacterium limosum KIST612 was cultivated on carbon monoxide using a cell- recycled continuous fermentation system to produce organic acids. A bubble column reactor system (k(L)a = 72 h(-1)) was used with a membrane to allow on-line products removal with cell recycle. When cell concentration reached 5.25 g l(-1) in the reactor, the cell concentration did not increase at ca rbon monoxide (CO) partial pressures lower than 74 kPa though CO was consum ed with the acidic products formation. At this stage, the overall CO mass t ransfer rate (k(L)a[C* - C-L]) was lower than required for the maximum cell growth (q(CO)(X)(max) but higher than that to meet the maintenance require ment (m(s)X). When the CO mass transfer rate was maintained higher than mai ntenance requirement by increasing CO partial pressure, the cell concentrat ion increased to 9.5 g l(-1). (C) 2001 Elsevier Science Ltd. All rights res erved.