► Production of lactobionic acid from whey by Pseudomonas taetrolens. ► Enhancement in terms of bioconversion yield was achieved by varying inoculum size. ► Bioconversion efficiency was highly depended on inoculum age. ► A pH-shift cultivation strategy has enabled complete lactose bioconversion. ► Growth phase was featured by broth alkalinization and decrease in dissolved oxygen. Lactobionic acid finds applications in the fields of pharmaceuticals, cosmetics and medicine. The production of lactobionic acid from whey by Pseudomonas taetrolens was studied in shake-flasks and in a bioreactor. Shake-flask experiments showed that lactobionic acid was a non-growth associated product. A two-stage pH-shift bioconversion strategy with a pH-uncontrolled above 6.5 during the growth phase and maintained at 6.5 during cumulative production was adopted in bioreactor batch cultures. An inoculation level of 30% promoted high cell culture densities that triggered lactobionic acid production at a rate of 1.12g/Lh. This methodology displayed efficient bioconversion with cheese whey as an inexpensive substrate for lactobionic acid production.