No abstract

To evaluate bile salt hydrolase activities, changes in the internal pH and cell survival to bile acids in lactic acid bacteria to establish the relationship between these parameters.

No abstract

SummaryIn this work, autochthonous lactic acid bacteria (LAB) were isolated from chia (Salvia hispanica L.) dough and selected on the basis of the kinetics of acidifi cation and proteolytic activity. Strain no. C8, identifi ed as Lactobacillus plantarum C8, was selected and used as start er to obtain chia sourdough. Lactic acid fermentation increased the organic acid mass fractions (lactic, acetic and phenyl lactic acids to 12.3 g, 1.0 g and 23.8 μg per kg of dough respectively), and antioxidant activities, which increased by approx. 33-40 % compared to unfermented chia fl our dough. In addition, total phenolic content increased 25 % and its composition was strongly modifi ed aft er 24 h of fermentation by L. plantarum C8. Chlorogenic acid was only found in the fermented dough (2.5 mg/g), while ferulic acid was detected from the beginning of fermentation, being 32 % higher in chia sourdough (5.6 mg/g). The use of fermented chia sourdough improved the overall characteristics of white bread, including physical (e.g. reduced hardness and chewiness of the crumb) and antioxidant properties (25 % on average), compared to the white bread. These results indicate that the use of chia sourdough could be a promising alternative to improve the technological and antioxidant properties of wheat bread. In addition, this work has shown, for the fi rst time, that lactic acid bacterium is able to ferment chia dough, improving its overall characteristics.

To study whether an active bile acid (BA) efflux occurs in Lactobacillus reuteri CRL 1098 as well as the nature (ATP or proton motive force [PMF] mediated primary transport) of the BA extrusion mechanism. BAs are powerful detergents which disorganize the lipid bilayer structure of cellular membranes. Specific bile resistance mechanisms (bile efflux, bile salt hydrolysis, and intrinsic architecture and composition of cell membrane the most prevalent) have been described in intestinal bacteria. L. reuteri, showed a significant degree of resistance to the toxic action of BA and the presence of an active efflux ATP-dependent of conjugated (taurocholic [TCA]) and free (cholic [CA]) BA in the CRL 1098 strain is now reported. However, due the high pKa (5.5) of cholic acid (CA) compared with the conjugated species, a significant fraction (between 35 and 50% at pH 6.5 and 5.2, respectively) of free BA also diffused passively, even in the absence of ATP. To our knowledge, our results represent the first evidence of ATP as the energy source involved in the BA extrusion in L. reuteri.