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

• Amphiphilic water-soluble polymers from Botryococcus braunii formed emulsions.
• The water-soluble polymer content should be < 0.5% for hydrocarbon recovery.
• The water-soluble polymers were polysaccharides with a molecular weight of > 2 × 106.
• The polymers were mainly comprised of galactose, arabinose, and uronic acid.

Water-soluble polymers are released from the extracellular matrix of Botryococcus braunii by thermal pretreatment prior to hydrocarbon extraction. In this study, hydrocarbon recovery was reduced by adding polymers to algal slurries from which they were previously washed. The water-soluble polymers are amphiphilic and emulsify the water–organic solvent systems used in hydrocarbon extraction. To obtain > 90% hydrocarbon yields from high-concentration slurry, the original 10% water-soluble polymer content of dry algal cells had to be reduced to less than 0.5%. The water-soluble polymers were polysaccharides with a molecular weight greater than 2 × 106 and mainly comprised of galactose, arabinose, and uronic acid. We suggest that high-molecular-weight water-soluble polymers are desirable as industrial emulsifiers and thickeners.

Interaction between the water-soluble polymers from Botryococcus braunii and extraction solvent. Aqueous solution of water-soluble polymers (concentration, 0.5 wt.%) and n-hexane were combined at a ratio of 1:1 (vol/vol). (a) Before stirring, n-hexane and the aqueous solution formed two layers. (b)Vigorous stirring resulted in the formation of an emulsion. (c)After being left to stand for 18 h, the hexane layer showed a gel (hardening) state. We suggest that high-molecular-weight water-soluble polymers from B. braunii have potentials as industrial emulsifiers or thickeners.Figure optionsDownload as PowerPoint slide