Dimorphism of oleaginous yeast Meyerozyma guilliermondii during single-cell oil production under decanoic acid stress.

Meyerozyma guilliermondii is an oleaginous yeast capable of accumulating lipids, yet there are limited studies on its utilization of fatty acids as a carbon source. In this study, the ability of M. guilliermondii to utilize various fatty acids was evaluated, and the strain did not grow in the presence of decanoic acid (C10) during initial screening. The effects of C10 on growth, morphology, and lipid accumulation were investigated. Culturing M. guilliermondii in complex medium supplemented with 0.5 g/L of C10 at 0 h resulted in a significantly prolonged lag phase and induction to a morphological transition from yeast-like cells to pseudohyphal structures once growth resumed. Despite growth inhibition and morphological changes, lipid accumulation and fatty acid composition remained comparable to control, and C10 was not incorporated into lipids. C10 exposure was associated with reactive oxygen species (ROS) accumulation and upregulation of SOD, ATG1 and ATG9 genes, suggesting that oxidative stress and autophagy contribute to stress adaptation as a response to C10 exposure. YPD1 expression was also upregulated in the HOG pathway, although its interaction with oxidative stress-related transcription factors remains unclear. These findings highlight M. guilliermondii as a resilient strain capable of adapting to environmental stress.