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We studied high-density cultures of Pseudomonas putida IPT 046 for the production of medium-chain-length polyhydroxyalkanoates (PHA_MCL) using an equimolar mixture of glucose and fructose as carbon sources. Kinetics studies of P. putida growth resulted in a maximum specific growth rate of 0.65h⁻¹. Limitation and inhibition owing to NH₄ ⁺ ions were observed, respectively, at 400 and 3500 mg of NH₄ ⁺/L. The minimum concentration of dissolved oxygen in the broth must be 15% of saturation. Fed-batch strategies for high-cell-density cultivation were proposed. Pulse feed followed by constant feed produced a cell concentration of 32 g/L in 18 h of fermentation and low PHA_MCL content. Constant feed produced a cell concentration of 35 g/L, obtained in 27 h of fermentation, with up to 15% PHA_MCL. Exponential feed produced a cell concentration of 30 g/L in 20 h of …