Influence of temperature and growth phase on desaturase activity of the mesophilic yeast Candida lipolytica.

Microsomal membranes prepared from Candida lipolytica cells grown at 10 degrees C had a higher lipid content and degree of unsaturation than membranes prepared from cells grown at 25 degrees C. The specific activities of stearoyl-CoA (18:0-CoA), oleoyl-CoA (18:1-CoA), and dioleoyl phosphatidylcholine (18:1-PC) desaturases in microsomes of cells grown at either 25 or 10 degrees C showed maximum values near midlog phase, coinciding with the respective maximum absolute content of linoleic (18:2) in the microsomal preparations. The 18:1-CoA desaturase activity in 10 degrees C cells was nearly double that in 25 degrees C cells, while the 18:0-CoA and 18:1-PC desaturases had considerably lower activities in 10 degrees C cells. An increase in aeration rate (shaking speed, 70 to 130 rpm) resulted in increased proportions of 18:2 (32 to 47%, respectively) in microsomes of cells grown at 25 degrees C and in increased 18:1-CoA desaturase specific activity (83 to 140 pmol X min-1 X mg-1); however, no significant changes occurred in 18:0-CoA or 18:1-PC desaturase activities.