Conversion of Cholesterol to Pro- Vitamin D3 Derivatives by Tetrahymena termophila Cells Grown in Media Containing Milk or Egg Yolk

GERMAN VALCARCE; ALEJANDRO NUSBLAT; LUCIANA MUÑOZ; CLARA B. NUDEL; JORGE FLORIN-CHRISTENSEN

Orlando Florida, EEUU

Congreso; American Society for Microbiology (ASM) 101th General Meeting; 2001

American Society for Microbiology

Tetrahymena is one of the few organisms in which the desaturation of cholesterol to pro-vitamin D3 derivatives has benn observed. This peculiar activity has remarkable biotehnological potential for use in selective methods for cholesterol removal from dairy products and other foodstuffs of animal origin.In cultures of T. termophila containing 70-90 % whole milk (cholesterol concentratrion 0,14 mg/ml) 80 % of the cholesterol initially present was removed and transformes to D7 dehydrocholesterol (5%) and D7,22 (bis) dehydrocholesterol (75%). Cultures of the same strain in medium supplemented with 1,2 % crude egg (cholesterol concentration 0,36 mg/ml) resulted in 65 % cholesterol reduction, with the simultaneous formation of D7 dehydrocholesterol (61%). Incubations were always performed at 28C during 40 hs, and the sterol content was measured in cell extracts upon saponification. Controls containing solely cell extracts or uninoculated culture medium showed no cholesterol conversions.Kinetic studies of the process showed that maximal accumulation of D7dehydrocholesterol was achieved at 4 hs. incubation, decreasing in further stages as the culure proceeded. On the other hand, D7,22 (bis) dehydrocholestrol formation was low up to 4Hs culture but increased sharply upon further incubation, reaching a maximum at 8 hs.Conclusion: Cholestrol contained in foodstuffs is accessible to the protozoon and rapidly converted to desaturated forms, including pro-vitamin D3. Thus, ciliate suspensions can be used as novel means for foodstuff improvement.