Investigation of the Wet Extraction of Hydrocarbons from a Heterotrophic Microalga, Aurantiochytrium sp. 18W-13a, by Cell Disruption Using a High-pressure Homogenizer

Aurantiochytrium, a heterotrophic microalga, produces hydrocarbons inside its cells and has a higher growth rate than other photosynthetic microalgae. To investigate a possible method of extracting hydrocarbons from wet Aurantiochytrium cells, cell cultures of Aurantiochytrium were treated with a high-pressure homogenizer. The influence of cell disruption and extraction time on the cell morphology, hydrocarbon yield, and energy balance of hydrocarbon extraction was evaluated. The hydrocarbon yield increased with an increase in extraction time regardless of cell disruption. After one round of the homogenizing treatment in which cells were fragmented (one-pass treatment), a second round (two-pass treatment) did not cause any additional morphological change. For the 40-min extraction, the yield of hydrocarbon from disrupted samples was found to be over ten times higher than that of undisrupted ones. In contrast, for the 180-min extraction, the yield of undisrupted samples was almost the same as that of disrupted ones because the cells of Aurantiochytrium were disrupted by extended contact with n-hexane over the longer extraction time. Furthermore, the input energy of the 40-min extraction with cell disruption was 78% lower than that of the 180-min extraction without cell disruption to obtain almost the same hydrocarbon yield.