Phytate-degrading activity of probiotic bacteria exposed to simulated gastrointestinal fluids

Modulatory Effect of the Intracellular Content of Lactobacillus casei CRL 431 Against the Aflatoxin B1-Induced Oxidative Stress in Rats

It has been recognized that lactic acid bacteria exhibit antioxidant properties, which have been mainly endorsed to the intact viable bacteria. However, recent studies have shown that intracellular content (IC) may also be good sources of antioxidative metabolites, which may potentially contribute to oxidative homeostasis in vivo. Hence, the modulatory effect of the intracellular content of Lactobacillus casei CRL 431 (IC431) on aflatoxin B₁ (AFB₁)-induced oxidative stress in rats was evaluated on the basis of its influence on hepatic lipid peroxidation (LPO), antioxidant status-antioxidant capacity (TAC), catalase (CAT), and glutathione peroxidase (GPx) activities; and on the oxidative stress index (OSi). Results demonstrated that CAT and GPx activities, and TAC, determined in plasma samples, were significantly (P < 0.05) higher in rats treated with AFB₁ plus IC431 (3.98 μM/min/mg protein, 1.88 μM/min/mg protein, and 238.7 μM Trolox equivalent, respectively) than AFB₁-treated rats (3.47 μM/min/mg protein, 1.46 μM/min/mg protein, and 179.7 μM Trolox equivalent, respectively). Furthermore, plasma and liver tissue samples from rats treated with AFB₁ plus IC431 showed significantly (P < 0.05) lower LPO values (52 and 51%, respectively) and OSi (59 and 51%, respectively) than AFB₁-treated rats. Hence, our results proved that the intracellular content of Lact. casei CRL 431 contains metabolites that are capable to modulate the antioxidant defense systems in living organism, which may help to ameliorate the damage associated to AFB₁-induced oxidative stress.

An in vitro chicken gut model for the assessment of phytase producing bacteria

An in vitro simulated chicken gut model was proposed for studying the phytase activity of selected bacteria such as Streptococcus thermophilus, Sporosarcina pasteurii, Sporosarcina globispora, and Sporosarcina psychrophila using known probiotic bacterium, Lactobacillus helveticus as a control. The selected bacteria were viable in the intestinal lumen and produced extracellular phytase at optimal phytate concentration of 6.25 mM when compared to 3.125 mM and 12.5 mM. These bacteria demonstrated significantly higher (p < 0.05) phosphate liberation (up to 387 µM) due to better phytase activity in the production medium, when compared to the growth medium (339 µM). The phytase activity showed a steady increase in phosphate liberation up to 150 min after which it became constant. This trend is observed for the selected bacteria at pH 5, 6 and 7. However, the liberation of phosphates showed no significant difference (p > 0.05) at the tested pH. Among the analyzed bacteria, the members of the genus Sporosarcina showed better phytate degradation when compared to S. thermophilus. The proposed model can be extended to analyze any extracellular enzymes produced by gut microbes.