Quantitative proteomic analysis of xylose fermentation strain Pichia stipitis CBS 5776 to lignocellulosic inhibitors acetic acid, vanillin and 5-hydroxymethylfurfural.

To obtain a global insight into the dynamic protein expression pattern in Pichia stipitis during xylose fermentation in the presence of three representative inhibitors (acetic acid, vanillin and 5-hydroxymethylfurfural), proteins were extracted for quantitative proteomic analysis using 8-plex isobaric tag for relative and absolute quantitation (iTRAQ) on a liquid chromatography-mass/mass spectrometry instrument. Interestingly, aconitase (Aco1p) and NAD-isocitrate dehydrogenase (Idh1p) were upregulated during the middle exponential phase in the presence of the three inhibitors during tricarboxylic acid cycle. We speculated that yeast cells adaptively increased the expression of the tricarboxylic acid cycle proteins to compensate for low NADH derived from glycolysis in the presence of the three inhibitors. Proteins related to amino acid metabolism, aminoacyl tRNA synthesis and stress response were also significantly affected in the presence of the three inhibitors. Taken together, quantitative proteomic analysis is capable of monitoring P. stipitis xylose fermentation under inhibitor conditions and identifying physiological changes, such as stress response.