In situ solid-liquid extraction enhances recovery of taxadiene from engineered Saccharomyces cerevisiae cell factories

Microbial cell factories express diverse heterologous pathways for the production of a wide range of valuable natural products. However, the recovery and purification of such compounds is a major bottleneck in commercialization. In this study, a novel in situ solid phase adsorption strategy was investigated for enhanced recovery of taxadiene, a precursor to the blockbuster anticancer drug, paclitaxel, from engineered Saccharomyces cerevisiae. A synthetic adsorbent resin (HP-20) was employed to efficiently sequester taxadiene as it was secreted during growth and a carefully optimized desorption solvent was applied following cultivation to maximize recovery of both secreted and intracellular taxadiene, across a range of scales (2 – 250 mL). Resin concentration was found to have an impact on cellular growth, with the high concentration of 12 % (w/v) resulting in fragmentation of the resin beads, which was detrimental to growth. The optimal resin concentration and desorption solvent combination elucidated at microscale (2 mL) resulted in a two-fold improvement in taxadiene titer to 61 ± 8 mg/L, compared to the traditional liquid-liquid extraction approach (dodecane overlay). Taxadiene was found to be distributed evenly between resin beads and biomass. Performance of the optimal process was subsequently investigated through scale-up using controlled mini-bioreactors (250 mL). Here, a comparable taxadiene titer of 76 ± 19 mg/L was achieved despite a 125-fold scale-up in cultivation volume. This represented a 1.4-fold improvement in taxadiene recovery compared to previous mini-bioreactor scale cultivations using the dodecane overlay extraction approach.