Influence of three ultrasound treatments on viability, culturability, cell architecture, enzymatic activity and metabolic potential of Lacticaseibacillus paracasei 90

PERALTA, G.H.; BÜRGI, M.; MARTÍNEZ, L.J.; ALBARRACÍND, V.H.; WOLF, I.V.; PEREZ, A.A.; SANTIAGO, L.; HYNES, E.R.; BERGAMINI, C.V.

INTERNATIONAL DAIRY JOURNAL

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2022

0958-6946

The effects of ultrasound treatments (UB, 1 h in an ultrasonic bath; UP3 and UP6, three and six 1 min- cycles, respectively, using an ultrasonic probe) on culturability, viability, cell architecture, and enzymatic activity of Lacticaseibacillus paracasei 90 (L90) were studied by cell counts, flow cytometry, scanning electron microscopy (SEM) and enzyme activity determinations. To evaluate the metabolic potential of the treated cells, milk was inoculated with treated or untreated bacteria, and incubated for 20 h at 37 °C. SEM revealed cellular damage in some UP-treated cells. Flow cytometry analysis and enzyme activity levels reflected an overall increase in permeability and lysis. UB increased the proteolytic activity of L90 and reduced its ability to produce acid. The damage of the cellular integrity caused by UP led to an increase in enzyme accessibility to the substrate, and it was positively correlated with enhanced diacetyl and acetoin production. In conclusion, the ultrasonic waves may be used to enhance the metabolic potential of starter and adjunct cultures. However, their effects should be previously checked as our findings depended on the equipment used (ultrasonic bath or ultrasonic probe) as well as the exposition time.