Abstract
We investigated the effect of sugar starvation treatment on the stress resistance of lactobacilli incubated in de Man, Rogosa, and Sharpe (MRS) medium without added glucose. Lactobacillus gasseri SBT2055 incubated in MRS medium in the absence of sugar showed higher survival rates at pH 3.6 or with 25 mg/L of hydrogen peroxide stored at 10℃. The expression levels of all the genes examined (atpD, cfa, clpC, dnaK, ftsH, groEL, hsp20, ldh, mscL, pox, opuA, ptsH, rpoD, trxA, uvrA) decreased after sugar starvation. On decreasing the pH of the medium, radical formation and a decrease in viable cell count were observed; however, the viability of sugar-starved cells improved and radical formation decreased at pH 3.6. Furthermore, from the six Lactobacillus species, only Lactobacillus gasseri and Lactobacillus johnsonii, incubated in MRS medium without added glucose at 37℃ for 18 h, showed an increase in viable cell count after 10 d of storage in a high sugar content solution (26% Brix) at 10℃. These results suggested that the sugar starvation pretreatment may provide a tool for improving the survival rate during processing and storage.
