## 3 Results and Discussion

Table 1: Production of lactic and acetic acids and pH values following 24 h cultivation and. Cytotoxic effects were determined using a mixed coculture of Caco-2/HT29 cells (ratio 9:1). According to [PERSON] et al. (2014) [PERSON] et al. (2014), extracts at IC50 \(>\) 90 \(\mathrm{\SIUnitSymbolMicro}\)/mL are considered nontoxic. Similar to our previous studies evaluating plant toxicity ([PERSON] et al., 2018; [PERSON] et al., 2018), we evaluated the effects of _Chlorella_ up to a concentration of 512 \(\mathrm{\SIUnitSymbolMicro}\)/mL; a similar method is commonly used in microbiological testing ([PERSON] et al., 2018). We observed that the IC50 was higher than 512 \(\mathrm{\SIUnitSymbolMicro}\)/mL and therefore concluded that the tested concentration of _C. vulgaris_ is safe. In comparison, it has been stated that polysaccharides isolated from _Chlorella_ show inhibitory activity on the HCT8 colorectal carcinoma cell line, corresponding to 3.14 mg/mL isolated exopolysaccharides at a yield of 364 mg/L depending on _Chlorella_ species ([PERSON] et al., 2018). The hypocholesterolem effects of _Chlorella_ or its components have been demonstrated in numerous studies in animals (rats and mice) fed a high-fat diet or in humans ([PERSON] et al., 2018; [PERSON] et al., 2018; [PERSON] et al., 2018; [PERSON] et al., 2018); however, the mechanisms by which _C. vulgaris_ and algae influence lipid metabolism remain unclear. Daily administration of _Chlorella_ supplement (5 \(\mathrm{\SIUnitSymbolMicro}\)/day) in mildly hypercholesterolem adults significantly reduced serum lipid risk factors (TAG and total cholesterol); this effect was related to carotenoid (particularly lutein) concentrations, which limit the intestinal absorption of TAG ([PERSON] et al., 2018). The effect of _Chlorella_ powder and the indigestible fraction isolated from _Chlorella_ on the hepatic metabolism of cholesterol has also been evaluated, based on the enzymatic activity and mRNA levels of cytochrome P450 7A1 (CYP7A1), the rate-influencing enzyme in the main biosynthesis pathway that produces bile acids, and HMG-CoA reductase in male Wistar rats ([PERSON] et al., 2018). The _Chlorella_ fractions both increased _Cyp7a1_ mRNA levels in the liver and influenced the concentration of cholesterol in the serum and liver. In addition to water-soluble fibers, antioxidants such as chlorophyll, and carotenoids, _Chlorella_ also contain phospholipids and arginine, which can help to prevent or treat obesity, hypercholesterolemia, and cardiovascular and gastrointestinal diseases ([PERSON] et al., 2014; [PERSON] et al., 2018; [PERSON] et al., 2018). In the present study, we therefore also sought to test the influence of _C. vulgaris_ in combination with bovine postpartum and the probiotic strain _B. animals_ subsp. lactis_ BB-120 on lipid metabolism in hypercholesterolemia male rats. In addition, the concentrations of lipid parameters, such as TAG, total cholesterol (TC), lipoproteins (LDL, IDL, HDL, VLDL), and aminotransferasees (ALT and AST) were determined in serum and tissues at the midpoint and end of the experiment (8 weeks). Group IV showed significantly decreased TAG levels in the serum and aorta (\(p<0.05\)) after 8 weeks (Table 3), concordant with decreased VLDL concentration (Table 4). These effects may be related to the inhibition of hepatic fatty acid synthesis and TAG production leading to a limitation in the levels of VLDL ([PERSON] et al., 2018) [PERSON] et al. (2008) also demonstrated the positive influence of _C. vulgaris_-containing diets (5.0 and 10.0%) on lipid metabolism in Wistar rats fed a high-fat diet, in which serum total lipid and liver TAG levels were significantly lower in both tested groups than in the control group after nine weeks. However, the concentrations of AST and ALT did not differ among groups ([PERSON] et al., 2014), whereas in the present study, the serum AST and ALT levels were significantly decreased at the end of the experiment in all test groups (\(p<0.05\); Table 5).