Evaluation of the ability of fermented cactus pear juice to improve oxidative stress tolerance in yeast

Abstract

Cactus pears from Opuntiaficus-indica are strongly recommended in the human diet sincetheir nutritional and health-promoting features. Scientific evidencehas demonstrated the benefits from cactus pear ingestionwith special consideration about potentially active antioxidantphytochemicals. However, long-term storage represents the maindrawback to the commercialization of this fruit. Since in manyplaces cactus pears are consumed as juice, different procedureswere developed to prevent its spoilage. Lactic acid fermentationof cactus pear juice (CPJ) using autochthonous bacteria constitutesan important biotechnology for the exploitation of this fruit.The aim of this study was to evaluate the effect of fermented CPJ(F-CPJ) on oxidative stress tolerance of Saccharomyces cerevisiae.Methods: Lactobacillus plantarum S-811, an autochthonouslactic acid bacteria strain isolated from O. ficus-indica fruits fromNorthwest Argentina was used to fermented the juice. To evaluatethe antioxidant response induced by CPJ and F-CPJ, cultures of S.cerevisiae were incubated with the juices (amounts equivalent to 50,250 and 500 mg/L of phenolics) during 18 h at 28 °C. Cells were thenexposed to sub-lethal oxidative stress, using 0.5 or 4 mM H2O2. Afterstress treatments, cells were cultured in YPD medium and incubatedfor 18 h at 28 °C. To evaluate the oxidant effect in each culture,growth-ratio curves (GRC) and effect curves (EC) were constructedas follows: RC = quotient between the growth curve (GC) of theculture exposed to oxidant and the GC of the non-exposed culture;EC = GRC for the culture pre-incubated with the juice was dividedby the GRC for the culture pre-incubated without juice.Results: Against a final concentration of 0.5 mM H2O2 therewas not observed a significant protective effect by any of the evaluatedjuices. However, against 4 mM H2O2, CPJ and F-CPJ showeda significant protective effect, that was much higher with the F-CPJ(up to 15 times protection) than CPJ (up to 4 times protection).Conclusions: These results suggest that F-CPJ with L. plantarumS-811 could be a suitable choice for the development of a CPJwith improved functional properties.