Substrate versatility of Pseudomonas taetrolens was evaluated for the first time in a co-fermentation system combining cheese whey and glucose, glycerol or lactose as co-substrates. Results showed that P. taetrolens displayed different production patterns depending on the co-substrate supplied. Whereas the presence of glucose led to a simultaneous co-production of lactobionic (78 g/L) and gluconic acid (8.8 g/L), lactose feeding stimulated the overproduction of lactobionic acid from whey with a high specific productivity (1.4 g/g h) and yield (100%). Co-substrate supply of glycerol conversely led to reduced lactobionic acid yield (82%) but higher cell densities (1.8 g/L), channelling the carbon source towards cell growth and maintenance. Higher carbon availability impaired the metabolic activity as well as membrane integrity, whereas lactose feeding improved the cellular functionality of P. taetrolens. Insights into these mixed carbon source strategies open up the possibility of co-producing lactobionic and gluconic acid into an integrated single-cell biorefinery. (C) 2015 Elsevier Ltd. All rights reserved.