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

Abstract

Hydrocarbons are easily extracted by organic solvents such as n-decane from wet samples of Botryococcus braunii by thermal pretreatment at 90°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°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°C in samples that was pretreated at 70 or 80°C but not in those pretreated at 90°C. Furthermore, the pretreated >70°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°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.

Improving the Energy Balance of Hydrocarbon Production Using an Inclined Solid–Liquid Separator with a Wedge-Wire Screen and Easy Hydrocarbon Recovery from Botryococcus braunii

“…GC-electron impact mass spectrometry analysis (GCMS-QP2010, Shimadzu, Japan) with a capillary column (InertCap 1MS, GL Science, Japan) was carried out under the same temperature program as the GC-FID analysis. The major eight components that are typical of methylated squalene (C30-34 botryococcene) were identified in accordance with Atobe et al [28]. The number of peaks and hydrocarbon elution patterns were similar between the GC-FID and GC-MS.…”

“…The hydrocarbon mass dissolved in the recovered solvent was measured using programmed-temperature gas chromatography with flame ionization detection (GC-FID) by using a capillary column (GC-2014 with Rtx-1 capillary column, Shimadzu, Japan). The temperature program was as follows: the column was maintained at 50 • C for 1 min, heated from 50 to 220 • C at 10 • C min −1 , maintained at 220 • C for 3 min, heated from 220 to 260 • C at 2 • C min −1 , and equilibrated at 260 • C for 3 min [28]. The hydrocarbon mass was calculated from the sum of the peak areas corresponding to hydrocarbons relative to the peak areas for known amounts of standard hydrocarbons extracted and purified from freeze-dried algal samples; this process is described below.…”

Effect of amphiphilic polysaccharides released from Botryococcus braunii Showa on hydrocarbon recovery

“…We examined the thermophysical properties of the water-soluble polymers at 60, 70, 80, and 90°C. The water-soluble polymers of the thermally pretreated slurry eluted into the water phase at temperatures above the protein denaturation temperature (64°C) of algae [16].…”

The surface structure of Botryococcus braunii colony prevents the entry of extraction solvents into the colony interior

“…Fibrils were thought to have dissolved into hot water at 90°C. Atobe et al reported that the contents of arabinose and galactose, which were the constituents of saccharic components, increased when the colony was extracted with water at 90°C compared with that when the extraction was performed at 60°C [27]. After pre-heating at lower than 60°C, protein was not denatured, and the amount of hydrocarbon extracted was less.…”