•Ultrasound were used for a preliminary treatment of Lactiplantibacillus plantarum.•Ultrasound increased the extent of acidification of Lactobacillus plantarum c19 in vitro.•The ultrasound effect is attributed to an increased permeability of the membrane of treated cells. This paper focused on the evaluation of Ultrasound effect on the growth patterns (3–6% of salt and 45 °C), acidification (pH-decrease), interactions with microorganisms, and membrane permeability of nine strains of Lactiplantibacillus plantarum. Ultrasound treatment was applied at 20% of net power by modulating duration (2–10 min) and pulses (2–10 s). Viable count (7.15–8.16 log CFU/mL) was never affected by Ultrasound, while the treatment increased the extent of pH decrease of at least three strains (109, 162 and c19). L. plantarum c19 was the best performer, as a low intensity treatment was able to increase its acidification, without affecting its growth. The effects could be attributed to an increased permeability of the cellular membrane, as suggested by the increase of released intracellular components. Other factors should be further assessed (e.g. possible changes in the metabolism) and the performances of Ultrasound-treated strains in real brines.