Triacylglycerols are among the most attractive alternative raw materials for biofuel development. Current oil plant-based technologies are limited in terms of triacylglycerol production capacity and rate. These limitations may be circumvented by biotransformation of carbohydrates into lipids; however, our understanding of microbial oleaginicity remains limited. Here we present the results of a multi-omic analysis of Rhodosporidium toruloides, a robust triacylglycerol-producing fungus. The assembly of genome and transcriptome sequencing data reveals a genome of 20.2 Mb containing 8,171 protein-coding genes, the majority of which have multiple introns. Genes including a novel fatty acid synthase are predicted to participate in metabolic pathways absent in non-oleaginous yeasts. Transcriptomic and proteomic data suggest that lipid accumulation under nitrogen-limited conditions correlates with the induction of lipogenesis, nitrogenous compound recycling, macromolecule metabolism and autophagy. The multi-omic map of R. toruloides therefore provides a valuable resource for efforts to rationally engineer lipid-production pathways.

Acid in ionic liquid was demonstrated as an efficient system for hydrolysis of lignocellulosic materials with improved total reducing sugars (TRS) yield under mild conditions. TRS yields were up to 66%, 74%, 81% and 68% for hydrolysis of corn stalk, rice straw, pine wood and bagasse, respectively, in C₄mimCl in the presence of 7 wt% hydrogen chloride at 100 °C under atmospheric pressure within 60 min. Different combinations between ionic liquids, such as C₆mimCl, C₄mimBr, AmimCl, C₄mimHSO₄, and SbmimHSO₄, and acids, including sulfuric acid, nitric acid, phosphoric acid, as well as maleic acid, afforded similar results albeit longer reaction time was generally required comparing with the combination of C₄mimCl and hydrochloric acid. FT-IR spectra and elemental analysis of the recovered residues indicated that modification of lignin occurred during sulfuric acid catalyzed hydrolysis. In addition, kinetic modeling based on experimental data suggested that the hydrolysis likely followed a consecutive first-order reaction sequence, where k₁ and k₂, the rate constants for TRS formation and TRS degradation, were determined as 0.068 min⁻¹ and 0.007 min⁻¹, respectively. This novel system may be valuable to facilitate cost-efficient conversion of biomass into biofuels and biobased products.

Cytochrome P450 enzymes (CYPs) play major roles in generating highly functionalized terpenoids, but identifying the exact biotransformation step(s) catalyzed by plant CYP in terpenoid biosynthesis is extremely challenging. Tanshinones are abietane-type norditerpenoid naphthoquinones that are the main lipophilic bioactive components of the Chinese medicinal herb danshen ( Salvia miltiorrhiza ). Whereas the diterpene synthases responsible for the conversion of ( E,E,E )-geranylgeranyl diphosphate into the abietane miltiradiene, a potential precursor to tanshinones, have been recently described, molecular characterization of further transformation of miltiradiene remains unavailable. Here we report stable-isotope labeling results that demonstrate the intermediacy of miltiradiene in tanshinone biosynthesis. We further use a next-generation sequencing approach to identify six candidate CYP genes being coregulated with the diterpene synthase genes in both the rhizome and danshen hairy roots, and demonstrate that one of these, CYP76AH1, catalyzes a unique four-electron oxidation cascade on miltiradiene to produce ferruginol both in vitro and in vivo. We then build upon the previous establishment of miltiradiene production in Saccharomyces cerevisiae , with incorporation of CYP76AH1 and phyto-CYP reductase genes leading to heterologous production of ferruginol at 10.5 mg/L. As ferruginol has been found in many plants including danshen, the results and the approaches that were described here provide a solid foundation to further elucidate the biosynthesis of tanshinones and related diterpenoids. Moreover, these results should facilitate the construction of microbial cell factories for the production of phytoterpenoids.