Co-fermentation of carbohydrates and lignin in flowthrough-pretreated poplar to lipids with oleaginous Rhodococci

The main carbon sources in plant biomass are carbohydrates and lignin. Co-fermentation of carbohydrates and lignin to lipids is a prerequisite to obtain high carbon yield and to reduce biofuel costs. However, biotransformation of lignin to lipids is highly challenging due to its recalcitrant nature as a phenolic heteropolymer. A series of wild type and engineered Rhodococcus strains (e.g. R. opacus PD630, R. opacus DSM 1069, R. jostii RHA1, and R. jostii RHA1 VanV^-) with carbohydrate and lignin degradation and/or lipid biosynthesis capacities were selected to establish the functional modules that enable a platform for fundamental understanding of synergetic pathways of carbohydrate and lignin biological conversion to lipids. Co-fermentation of whole slurries of flowthrough pretreated poplar wood with and without simultaneous addition of cellulase was studied. Results suggested that the lipid yield increased with increasing microbial utilization of carbon from both carbohydrates and lignin as compared to the separate fermentation of carbohydrates and lignin. In addition, the potential synergetic metabolic pathways of carbohydrate and lignin will also be addressed in our presentation.