(191ba) Elucidation of Aromatic Metabolism Pathways in a Non-Model, Non-Conventional Oleaginous Yeast

Oleaginous yeasts have long been a target for developing industrial-scale biochemical processes due to their ability to accumulate high amounts of lipids, synthesize complex chemicals and proteins, and robustly metabolize diverse feedstocks. In parallel, interest in lignocellulosic biomass as a feedstock has grown. Trichosporon oleaginosus, previously known as Cryptococcus curvatus, is a non-model, non-conventional, oleaginous yeast that we have discovered both tolerates and metabolizes lignin-derived phenolics. We have characterized T. oleaginosus biomass and lipid accumulation while utilizing glucose, phenol, catechol, 4-hydroxybenzoic acid, and resorcinol as sole carbon sources under nitrogen rich and nitrogen starved conditions. Aromatic metabolism does not hinder lipid accumulation, but toxicity limits how much carbon can be dosed at a single time to 1 g/L for three of the four aromatics studied. As such, we explored different feeding strategies to overcome aromatic toxicity, and increased lipid accumulation by more than 85%. Since many recalcitrant waste streams are heterogeneous feedstocks, we also characterized growth and lipid accumulation when cells are cultured in dual carbon feedstocks, and found that feeding glucose and resorcinol at once improves lipid accumulation by 41% when compared to glucose as a sole carbon source. To date, the mechanism for aromatic metabolism in this yeast remains unknown. BLAST analysis suggests a potential putative pathway for metabolism of aromatic compounds, but non-intuitive qPCR results indicates the mechanism could involve a cryptic pathway or an alternative mechanism of aromatic metabolism. RNAseq data was utilized in effort to elucidate the pathways responsible for aromatic metabolism. In all, this work hopes to showcase this yeast as a potential model oleaginous yeast for aromatic metabolism, with future applications for valorization of recalcitrant feedstocks such as lignin and phenolic wastewater effluents.