Three experiments were conducted to study the effect of milk, Thermophilus milk and methanol solubles of milk and Thermophilus milk on the plasma cholesterol levels and hepatic cholesterogenesis using laboratory rats. In experiment I, white Wistar male rats of 3288 initial average weight were assigned to three dietary treatments consisting of: (1) commercial rat chow + water, (2) commercial rat chow + skim milk, and (3) commercial rat chow + Thermophilus milk. In the second experiment, the methanol solubles of whole milk and Thermophilus milk were given by gastric intubation to white Wistar male rats in six treatment groups. The methanol solubles were given at levels of 1 ml and 2 ml, and the control groups received similar quantities of H,O. In the third experiment, liver tissue from white Wistar male rats was used to study the in vitro hepatic cholesterol synthesis. Consumption of Thermophilus milk by the rats in experiment 1 resulted in a significant decrease in plasma cholesterol levels, The liver cholesterol levels were lower in the group receiving Thermophilus milk than the group receiving skim milk. Similar results were seen with feeding of methanol solubles. The in vitro hepatic cholesterogenesis was inhibited by methanol solubles from milk and Thermophilus milk, the inhibition being much more with methanol solubles from ThermophiZus milk. The metabolites produced during fermentation of milk may be responsible for the hypocholesterolemic effect of Thermophilus milk.

Skim milk fermented by various lactic cultures was tested for antimicrobial activity by agar diffusion technique, using Pseudomonas jluorescens, P. aeruginosa and Bacillus subtilis as test organisms. Lactobacillus bulgaricus, L. acidophilus and Streptococcus thermophilus strongly inhibited the growth of the test organisms. Other lactic cultures, singly or in combination, showed varying degrees of antimicrobial activity. A methanoi-acetone (M-A) extract was prepared by lyophilizing fermented milk and extracting the powder sequentially with cold methanol and acetone. The methanol-acetone (M-A) extract strongly inhibited the growth of B. subtilis, B. pumulis, P. aeruginosa, P. jluorescens, Flavobacterium capsulatum, Satmonella typhimurium, Escherichia coli, Shigella sp. and Streptococcus lactis. The antimicrobial activity of S. thermophilus was not reported in the literature previously. The M-A extract contained ninhydrin-positive materials and did not lose antimicrobial activity even when it was exposed to a temperature of 100°C for 10 min. Five milliliters of M-A extract were applied to 20 x 2.2 cm Sephadex G-10 column equilibrated with 0.05N HCl which later served as the eluant. Fractions of 15 ml were collected at a flow rate of 2.5 ml/mm Sephadex fractionation of M-A extract showed that there were at least three active fractions. One of the fractions appeared in the void volume followed closely by the other fractions indicating that the latter two fractions have compounds of molecular weight less than 700 daltons. The purification achieved was about 400-fold. The activity (recovery) of the compound(s) increased upon fractionation on Sephadex indicating the possible presence of inhibitor(s).

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In five dietary treatments 70 rats (146g) were fed: (1) chow + water, (2) chow + skim milk, (3) chow + skim milk fermented by Streptococcus thermophilus, (4) chow + skim milk fermented by Lactobacillus bulgaricus, and (5) chow + skim milk fermented by Lactobacillus acidophilus. After 4 wk of feeding, the mean levels of cholesterol in plasma (mg/dl) and whole body (mg/g dry matter) for treatments 1 through 5 were: 61.3, 54.7, 56.0, 57.