Leuconostoc IN FOOD INDUSTRY: PERFORMANCE AGAINST TECHONOLOGICAL STRESS CONDITIONS

A. QUIBERONI; D. GUGLIELMOTTI; D'ANGELO L.; VIVIANA B. SUÁREZ

San Miguel de Tucumán

Simposio; V Simposio Internacional de Bacterias Lácticas; 2016

Leuconostoc is a lactic acid bacteria (LAB)used as starter in several fermentative food processes, being also present in traditional cheeses asautochthonous non-starter lactic acid bacteria (NSLAB). High intrinsiccapacity of strains to survive and grow in adverse technological conditions(during storage or fermentative process) is essential to assure high number ofviable cells and adequate performance during fermentation. On the other hand,cells subjected to sub-lethal stress conditions (adaptation) could improvetheir resistance to the specific factor of adaptation and/or to other stressfactors. In a previous work, 12 out of 29 strains, which showed good resistanceagainst thermal, acidic, alkaline, osmotic and oxidative shocks, were selectedfor this study. Growth performance of these strains was evaluated in diversestress conditions: i) MRS broth, 24 h ? 30º C (control); ii) MRSbroth at pH 5.0 and 5.5, incubating at 30º C - 24 h (acidic stress); iii) MRSbroth at pH 8, incubating at 30º C - 24 h (alkaline stress); iv) MRS brothadded of NaCl 4 % (w/v), incubating at 30º C - 24 h (osmotic stress) and v) MRSbroth incubating at 10º C - 24 and 48 h (cold stress). Growth rates (GR, %) definedas O.D.s / O.D.c x 100 (O.D.s= optical densityof strain under stress condition and O.D.c= optical density ofcontrol cells, both measured at the end of the experience), were calculated. Six(6) strains, (Ln N6, Ln N19, Ln N12, Ln D2, Ln D11 and Ln MB7 in decreasing order) showed the better average growth ratevalues. Thermal adaptation (40º C ? 30 min, MRS broth) on four (4) out of thesesix (6) strains (Ln N19, Ln N12, Ln D2 and Ln D11) was performed.After heat adaptation, cells were subjected to thermal (55º C ? 15 min), acidic(pH 4, 30 min - 30º C) and oxidative (H2O2 0.3 % (p/v),30 min - 30º C) shock conditions. Afterwards, new GR (%) under the stressconditions previously described, were calculated. Strains Ln N12, Ln D2 and Ln D11 improved their shock resistance in1.43 - 1.84 (thermal) and 2.79 - 4.85 (acidic) log orders, while no changeswere observed for Ln N19. Regarding oxidativeshock, all strains diminished their resistance between 1.30 and 3.05 logorders. Growth rate values (%) increased for all strains with thermaladaptation, with variable values according to the strain and the stress factorconsidered (between 3.17 % and 53.2 %). In general, strain Ln N19 showed the highest increases in GR values after adaptation. Basedon these results, Ln N6 (Leuconostoc lactis) and Ln N12 (Leuconostoc mesenteroides) wereselected as the most suitable strains to resist conservation processes and growthtechnological stress conditions commonly applied in the fermentative food industry.