Use of a Doehlert factorial design to investigate the effects of pH and aeration on the accumulation of lactones by Yarrowia lipolytica

Aims: To detect rate- limiting steps in the production of lactones by studying the combined effect of pH and aeration on their accumulation. Methods and Results: A Doehlert experimental design was chosen to evaluate the accumulation of four lactones in the pH ( 3 center dot 5 - 7 center dot 3) and KLa ( 4 center dot 1 h(-1) to 26 h(-1)) experimental domain. The accumulation of c- decalactone was higher at pH around 5 and increased at low aeration reaching 496 mg l - 1 at pH 6 center dot 35 and KLa 4 center dot 5 h(-1). The specific accumulation increased at low aeration. The 3hydroxy- c- decalactone accumulation was higher at low pH and high aeration conditions: 660 mg l - 1 at pH 4 center dot 4 and 26 h (-1). For dec- 2- en- 4- olide and dec- 3- en4- olide, lower amounts were reached ( 104 mg l - 1 and 66 mg l - 1, respectively). Conclusions: Although the accumulation of the four lactones should be related to catalytic steps requiring oxygen, the accumulation of c- decalactone was higher in low aeration conditions whereas the one of 3- hydroxy- c- decalactone was promoted for high aeration. Decenolides accumulate independently of pH or aeration. Significance and Impact of the Study: This study gives new insights into the catabolism of lipids, such as the role of co- factor regulation and the fact that the 3- hydroxylactone dehydration step is insensitive to pH or aeration.