Application of RBGR--a simple way for screening of oxygen tolerance in probiotic bacteria.

Oxygen toxicity is a major problem in the survival of probiotic bacteria in dairy foods. High levels of oxygen in the product are detrimental to the viability of these predominantly anaerobic bacteria. Screening probiotic bacteria for oxygen tolerance before their incorporation could ensure high cell counts in food products during storage. Reported techniques have focused only on qualitative estimations of oxygen tolerance in probiotic bacteria. To characterize the oxygen tolerance of a large number of organisms, a quantitative measurement is essential. For the first time, the oxygen tolerance of several probiotic strains was measured quantitatively using an index known as Relative Bacterial Growth Ratio (RBGR). The tolerance to oxygen varied between organisms, and this technique can therefore be applied for screening probiotic bacteria for oxygen tolerance.