Journal Article

The effect of the water-soluble polymer released from Botryococcus braunii Show a strain on solvent extraction of hydrocarbon

Okada, Shigeru, Atobe, Sueko, Magota, Akinari, Hasegawa, Fumio, Imou, Kenji, Saga, Kiyotaka, Suzuki, Toru, Furuhashi, Kenichi

2015

Overview

Hydrocarbons are easily extracted by organic solvents such as n-decane from wet samples of Botryococcus braunii by thermal pretreatment at 90 degree C even after being cooled to room temperature. However, hydrocarbon recoveries are not as readily achieved at room temperature from samples pretreated at temperatures lower than 80 degree C. This suggests that there is the point of no return for pretreatment temperature that enables effective solvent extraction of hydrocarbons at room temperature from wet algal samples of B. braunii. To elucidate the mechanism of hydrocarbon recovery from B. braunii following thermal pretreatments, we investigated the thermophysical properties of the water phase separated from heated algal slurry. Differential scanning calorimetry (DSC) measurements revealed sol-gel transitions in the water phase of algal slurry after protein denaturation at 64 degree C in samples that was pretreated at 70 or 80 degree C but not in those pretreated at 90 degree C. Furthermore, the pretreated >70 degree C water-soluble polymers revealed polysaccharides composed of galactose, arabinose, and uronic acid. These results suggest that the transition from sol state to gel state of water-soluble polysaccharides in algal slurry prevented hydrocarbon recovery with organic solvents since hydrocarbons were easily recovered from sol state samples pretreated at 70 or 80 degree C when the extraction temperature was kept the same as the pretreatment temperature. These results reveal that the presence of water-soluble polymers with gelation ability in the water phase and removal of these polymers in sol state enable effective recovery of hydrocarbons at room temperature after thermal pretreatments.

• Subject: Botryococcus braunii