The ideal conditions of SCO study and production are with a
highly aerated bioreactor (e. g. a chemostat) in which pH and dissolved
oxygen (DO) values are well controlled (4). Moreover SCO
fermentation is a process that presents significantly high oxygen
demand (5). Concerning fermentations done in shake-flasks
for Y. lipolytica, even though care was taken to carry out cultures
in controlled pH and relatively high DO concentrations in the
medium (3), the low O2 transfer can potentially impose limitations
in lipid synthesis (4). In the case of Y. lipolytica cultures on
shake-flasks, the potential for unsatisfactory O2 transfer could
lead to changes in gene expression resulting in down-regulation
of proteins with crucial importance for the process of lipid accumulation
(e. g. ACL, acetyl-CoA carboxylase, NADPH+-malic
enzyme) (4), the latter potentially resulting in unsatisfactory
SCO accumulation. In contrast, given that citric acid was synthesized
in non-negligible quantities, enzymes responsible for the
synthesis of citric acid (e. g. citrate synthase) should be less sensitive
to unsatisfactory O2 transfer in the flask experiments