No abstract

Microbial oils can be used for biodiesel production and fumaric acid (FA) is widely used in the food and chemical industries. In this study, the production of lipids and FA by Aureobasidium pullulans var. aubasidani DH177 was investigated. A high initial carbon/nitrogen ratio in the medium promoted the accumulation of lipids and FA. When the medium contained 12.0% glucose and 0.2% NHNO, the yeast strain DH177 accumulated 64.7% (w/w) oil in its cells, 22.4 g/l cell biomass and 32.3 g/l FA in a 5-L batch fermentation. The maximum yields of oil and FA were 0.12 g/g and 0.27 g/g of consumed sugar, respectively. The compositions of the produced fatty acids were C (0.6%), C (24.9%), C (4.4%), C (2.1%), C (57.6%), and C (10.2%). Biodiesel obtained from the extracted oil burned well. This study provides the pioneering utilization of the yeast strain DH177 for the integrated production of oil and FA.

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BcHpt is a core element of the high-osmolarity glycerol (HOG) transduction pathway in Botrytis cinerea. In contrast to other elements of the pathway, which have been characterized and proven to play important roles in vegetative differentiation, fungicide resistance, the multistress response, and virulence in B. cinerea, BcHpt (Histidine-containing phosphotransfer) is essential but uncharacterized in B. cinerea. Our previous study reported the first lysine acetylation site (Lys161) in BcHpt. In this study, the functions of this lysine acetylation site in BcHpt were characterized using site-directed mutagenesis. To mimic Lys161 acetylation, we generated the mutant strain BcHPt + BcHpt K161Q -GFP, which exhibited a slower growth rate; lower pathogenicity; higher sensitivity to multiple stresses, including osmotic and oxidative stresses, dicarboximides, and demethylation inhibitors (DMIs); and lower BcSak1 phosphorylation levels than wild-type B. cinerea. Constitutive acetylation of BcHpt Ly161 apparently inhibits hyphal growth, the multistress response, and sensitivity to fungicides in B. cinerea. Moreover, the lysine acetylation site affected phosphorylation of the MAPK BcSak1.

Yarrowia lipolytica is an oleaginous yeast for the production of oleochemicals and biofuels. Nitrogen deficiency is beneficial to lipids biosynthesis in Y. lipolytica. Target of rapamycin (TOR) regulates the utilization of nutrients, which is inhibited in nitrogen starvation or by rapamycin treatment. However, under nitrogen-rich conditions, the lipids biosynthesis in Y. lipolytica after inhibition of TOR by rapamycin is elusive. Combining metabolomics and transcriptomics analysis, we found that rapamycin altered multiple metabolic processes of Y. lipolytica grown in nitrogen-rich medium, especially the metabolisms of amino acids and lipids. A total of 176 differentially accumulated metabolites were identified after rapamycin treatment. Rapamycin increased the levels of tryptophan, isoleucine, proline, serine, glutamine, histidine, lysine, arginine and glutamic acid, and decreased the levels of threonine, tyrosine and aspartic acid. Two fatty acids in lipid droplets, stearic acid (down-regulated) and stearidonic acid (up-regulated), were identified. The expression of 2224 genes changed significantly after rapamycin treatment. Further analysis revealed that rapamycin reduced carbon flux through lipids biosynthesis, accompanied by increased carbon flux through fatty acids degradation and amino acid (especially glutamic acid, glutamine, proline and arginine) biosynthesis. The dataset provided here is valuable for understanding the molecular mechanisms of amino acid and lipids metabolisms in oleaginous yeast.