Optimization of submerged culture conditions for the production of angiotensin converting enzyme inhibitor from Flammulina velutipes.

The angiotensin-converting enzyme (ACE) inhibitory effect was tested in the culture broth from submerged mycelial cultures of 20 basidiomycetes. The ACE inhibitory effect of culture broth from Flammulina velutipes strain 414 was the highest (52.8%), followed by Lentinus edodes strains 2 (44.4%) and 16 (41.3%). Nutritional requirements for the production of ACE inhibitory substance from F. velutipes were studied. Sucrose, ammonium acetate, and glutamic acid were chosen for the maximum production of ACE inhibitory substance. The optimal medium composition was (g/l): sucrose 20, ammonium acetate 5, glutamic acid 2, KH(2)PO(4) 3, MgSO(4).7H(2)O 0.8, and yeast extract 0.5. Under optimal culture conditions, the ACE inhibitory effect was more than 80%.

Incorporation of cholesterol into the cellular membrane of Lactobacillus acidophilus ATCC 43121.

Cholesterol that was assimilated by Lactobacillus acidophilus ATCC 43121 was not metabolically degraded; most of it was recovered with the cells. Cells that were grown in the presence of cholesterol micelles and bile salts were more resistant to lysis by sonication than were those grown in their absence, suggesting a possible alteration of the cell wall or membrane. Cholesterol assimilation occurred during growth at pH 6.0 as well as during growth without pH control. Part of the cholesterol that was assimilated by cells was recovered in the membrane fractions of cells grown under both conditions. There was no difference in the amount taken up from cholesterol micelles that were prepared using dioleoyl L-alpha-phosphatidylcholine or distearoyl L-alpha-phosphatidylcholine. Thus, the type of fatty acid (unsaturated or saturated) in the phospholipid did not influence the assimilation. As the amount of Tween 80 in the growth media increased beyond 0.05%, cholesterol uptake decreased, and the amount of growth remained the same. The higher concentrations of Tween 80 may have adversely affected the permeability of the cells.

Influence of bile on beta-galactosidase activity of component species of yogurt starter cultures.

The influence of bile on beta-galactosidase activity and the cellular integrity of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus salivarius ssp. thermophilus were tested. Two strains (OS 1 and OS 2) of L. delbrueckii ssp. bulgaricus and three strains (HC 15, 17, and 18) of S. salivarius ssp. thermophilus were studied. In the presence of .15% oxgall, beta-galactosidase activity of whole cells of both species was significantly increased. However, at a higher concentration (.3% oxgall), the beta-galactosidase activity was significantly less than in the presence of .15% oxgall. The presence of oxgall did not promote the cell lysis of any of the strains of either species. Additionally, the presence of oxgall did not cause the leakage of the enzyme from the cells. Thus, the presence of oxgall increased the cellular permeability to allow more substrate to enter the cells, thereby increasing beta-galactosidase activity, and, at higher concentrations, was inhibitory to beta-galactosidase activity of both species.

Influence of bile on cellular integrity and beta-galactosidase activity of Lactobacillus acidophilus.

The influence of bile on beta-galactosidase activity, cellular integrity, cellular retention of beta-galactosidase, and cellular permeability of five strains of Lactobacillus acidophilus was investigated. The five strains were also compared for bile tolerance. Two strains, 223 and 4356, were significantly less resistant to bile than the others (107, NCFM, and 606). beta-Galactosidase activity of all five strains was significantly higher in the presence of .3% oxgall than in its absence. Strain 107 showed the highest increase of enzyme activity in the presence of oxgall. Cells were not lysed in the presence of .3% oxgall, and beta-galactosidase was retained inside the cell even after extended incubation (60 min) in the presence of .3% oxgall. However, material that absorbed light at 260 nm leaked from the cells in the presence of oxgall. We concluded that, in the presence of bile, the permeability of cells of L. acidophilus increased, permitting more substrate to enter the cells, thus increasing the beta-galactosidase activity of whole cells.