Leuconostoc in food industry: performance against technological stress conditions

D'ANGELO, LUISA; GUGLIELMOTTI, DANIELA MARTA; MERCANTI, DIEGO JAVIER; QUIBERONI, ANDREA DEL LUJÁN; SUÁREZ, VIVIANA

Tucumán

Simposio; V Simposio Internacional de Bacterias Lácticas; 2016

Cerela

Leuconostocisa lactic acid bacteria (LAB) used as starter in several fermentative foodprocesses, being also present in traditional cheeses asautochthonous non-starter lactic acid bacteria (NSLAB). High intrinsic capacityof strains to survive and grow in adverse technological conditions (duringstorage or fermentative process) is essential to assure high number of viable cellsand adequate performance during fermentation. On the other hand, cellssubjected to sub-lethal stress conditions (adaptation) could improve theirresistance to the specific factor of adaptation and/or to other stress factors.In a previous work, 12 out of 29 strains, which showed good resistance againstthermal, acidic, alkaline, osmotic and oxidative shocks, were selected for thisstudy. Growth performance of these strains was evaluated in diverse stressconditions: i) MRS broth, 24 h ? 30º C (control); ii) MRS broth at pH 5.0and 5.5, incubating at 30º C - 24 h (acidic stress); iii) MRS broth at pH 8,incubating at 30º C - 24 h (alkaline stress); iv) MRS broth added of NaCl 4 %(w/v), incubating at 30º C - 24 h (osmotic stress) and v) MRS broth incubatingat 10º C - 24 and 48 h (cold stress). Growth rates (GR, %)defined as O.D.s / O.D.c x 100 (O.D.s= opticaldensity of strain under stress condition and O.D.c= optical densityof control 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) wasperformed. After heat adaptation, cells were subjected to thermal (55º C ? 15min), acidic (pH 4, 30 min - 30º C) and oxidative (H2O2 0.3% (p/v), 30 min - 30º C) shock conditions. Afterwards, new GR (%) under thestress conditions previously described, were calculated. Strains Ln N12, Ln D2 and Ln D11 improvedtheir shock resistance in 1.43 - 1.84 (thermal) and 2.79 - 4.85 (acidic) logorders, while no changes were observed for LnN19. Regarding oxidative shock, all strains diminished their resistancebetween 1.30 and 3.05 log orders. Growth rate values (%) increased for allstrains with thermal adaptation, with variable values according to the strainand the stress factor considered (between 3.17 % and 53.2 %). In general,strain Ln N19 showed the highestincreases in GR values after adaptation. Based on these results, Ln N6 (Leuconostoc lactis) and Ln N12(Leuconostoc mesenteroides) were selected as the most suitablestrains to resist conservation processes and growth technological stressconditions commonly applied in the fermentative food industry.