**Acknowledgements**

*Prebiotics and Probiotics - Potential Benefits in Nutrition and Health*

is probably impossible to occur under in vivo conditions.

**intestinal fluid**

of dead bacterial cells.

**8. Conclusions**

released bile acids, independent of the amount of cells in the culture.

biomass. Therefore, Ziarno [4] demonstrated that in not all of the tested *Lactococcus* cultures the degree of biomass concentration had a significant influence on the amount of cholesterol removed. This can be explained by the activity of enzymes such as BSH, which caused bile hydrolysis and coprecipitation of cholesterol with

The chemical composition of simulated intestinal fluid seems to be of significance for the obtained results [18]. This indicates additional methodological factors influencing the results obtained in laboratory experiments conducted under in vitro conditions. In order to prepare simulated intestinal fluid, cattle bile was also used containing conjugated and deconjugated bile salts; therefore bile salt hydrolase activity (produced by the majority of intestinal lactic acid bacteria strains) was not necessary for cholesterol precipitation with free bile acids to occur [30, 35, 39, 40, 45]. Active BSH enzyme results in hydrolysis of bile salts, whereas cholesterol molecules may coprecipitate with the released bile acids [16, 17, 21, 30, 35, 39, 40, 45, 49, 50]. Such phenomenon has been observed in numerous lactic acid bacteria species, but not in *Lactococcus* thus far [49, 53]. It is known that coprecipitates of cholesterol with bile acids are formed at a low pH below 5.5 [17, 18, 21, 39, 49, 52]. However, with a renewed increase of pH to over 5.5, such coprecipitates were rapidly dissolved [15, 18, 28, 39]. Bile secreted from the liver is introduced to the duodenum, where it neutralizes the acidic food pulp that leaves the stomach and then the pH in the small intestine has a value of over 6.0. Under these conditions, the coprecipitates of bile acids and cholesterol are dissolved. Thus, the hypocholesterolemic effect caused by cholesterol coprecipitation with deconjugated bile acids

**7.4 Release of cholesterol bound by** *Lactococcus* **in the conditions of simulated** 

Ziarno [4] studied whether the cholesterol previously bound by *Lactococcus* cells is released under the conditions of simulated intestinal fluid. It was determined that certain isolates of *Lactococcus lactis* released up to 60–90% of cholesterol, which was earlier bound by these cells. Lower amount of cholesterol under conditions of simulated intestinal fluid is released by *Lactococcus lactis* cells (average of 45%), meaning that in these bacteria cultures cholesterol was bound with sufficient force by the cell wall so that it was not released under the conditions of simulated intestinal fluid. This may confirm the hypothesis of Lee et al. [84] on structural changes in the wall

One important conclusion should be drawn from the research results presented above, namely, that lactic acid bacteria may cause a different hypocholesterolemic effect in the human digestive system. They may exhibit a clear capacity for permanent binding and removal of cholesterol or to not bind it at all. It is also possible that they may cause such change of the intestinal microflora. Hosono et al. [14] formed a hypothesis that lactic acid bacteria may influence the amount of cholesterol eliminated from the organism despite the fact that they do not have the capacity to transform it into coprostanol. This is an effect of the influence of lactic acid bacteria on other microorganisms present in the intestinal microflora, including microorganisms capable of transforming cholesterol into coprostanol. This is particularly possible in the case of probiotic strains of lactic acid bacteria and bifidobacteria, which are distinguished due to their capacity to produce low-molecular antimicrobial

**88**

This work was supported by a grant from Warsaw University of Life Sciences (WULS-SGGW).
