A process of much future-potential for upgrading of biofuels derived from hydrothermal liquefaction (HTL) is catalytic hydrotreatment. HTL bio-oil, manufactured from Chlorella microalgae in a reactor operating in continuous flow mode was processed via hydrotreatment using a bio-Pd/C catalyst. This catalyst comprises a bacterial biomass support decorated with Pd(0) nanoparticles. The hydrotreatment performance of commercial Pd/C catalyst and bio-Pd/C was compared in order to benchmark the latter catalyst preparation. Oil: catalyst ratio, time and temperature were investigated as three variables for optimization. Similar conversion was observed for both Pd/C (76% liquid yield, 4.2% O) and bio-Pd/C (77% liquid yield, 3.9% O) catalysts under equivalent conditions (4 h reaction time, 5 wt% Pd loading, 325 degrees C). The oxygen content was reduced by 65%, whilst the nitrogen content decreased by 35%, with a bio-oil: catalyst ratio of 20, at a temperature of 325 degrees C and reaction time of 4 h. The upgraded oil was further studied by elemental analysis, Simulated Distillation and GC-MS, in order to quantify the improvement in fuel properties. The fresh and spent catalysts were analyzed using elemental analysis, TGA and ICP-MS, showing that the bio-oil yield was augmented by conversion of the biomass component from bio-Pd/C.