The profitable production of gluconic acid (GA), an organic acid extensively used in the food and beverages industries, relies on the use of cheap and available substrates with high sugar content. The high oxygen demand for the microbial conversion of glucose to GA is still a bottleneck of industrial production in conventional stirred-tank reactors. Therefore, in this study, for the first time, the effect of increased air pressure up to 4 bar on GA production and sugar consumption in batch and step-wise fed-batch cultures in sugarcane molasses (ScM) and grape must (GM) medium was studied.