Escherichia coli high-cell-density culture: carbon mass balances and release of outer membrane components

Carbon mass balances were calculated in fed-batch cultures of E. coli W3110, using mineral medium with glucose as the limiting substrate. The carbon recovery, based on biomass, CO(2), and acetate was approximately 90% at the end of the culture (25 h, 27 g L(-1) dw). The missing carbon remained as soluble organic compounds in the medium. Outer membrane (OM) constituents, such as lipopolysaccharides (LPS), phospholipids (PL), and carbohydrates (each at approximately 1 g L(-1)) contributed to 63% of the extracellular carbon. The amount of released LPS and PL equaled the total amount of OM bound to the cells in the culture. Small amounts of DNA and protein detected in the medium indicated that no cell lysis had occurred. Acetate, lactate, ethanol, formate, succinate and amino acids (Glu, Gln, Asp, Asn, Ala, Gly, Ser) were detected in the culture medium, but made up only a few percent of the extracellular carbon mass. The remaining 30% was not identified, but was assumed to constitute complex carbohydrates.