Seawater-Cultured Botryococcus braunii for Efficient Hydrocarbon Extraction

Abstract

As a potential source of biofuel, the green colonial microalga Botryococcus braunii produces large amounts of hydrocarbons that are accumulated in the extracellular matrix. Generally, pretreatment such as drying or heating of wet algae is needed for sufficient recoveries of hydrocarbons from B. braunii using organic solvents. In this study, the Showa strain of B. braunii was cultured in media derived from the modified Chu13 medium by supplying artificial seawater, natural seawater, or NaCl. After a certain period of culture in the media with an osmotic pressure corresponding to 1/4-seawater, hydrocarbon recovery rates exceeding 90% were obtained by simply mixing intact wet algae with n-hexane without any pretreatments and the results using the present culture conditions indicate the potential for hydrocarbon milking.HighlightsSeawater was used for efficient hydrocarbon extraction from Botryococcus braunii. The alga was cultured in media prepared with seawater or NaCl. Hydrocarbon recovery rate exceeding 90% was obtained without any pretreatment.

Culture of the green microalga Botryococcus braunii Showa with LED irradiation eliminating violet light enhances hydrocarbon production and recovery

“…In addition, there is a report demonstrating that hydrocarbon recovery was facilitated by changing the composition of the nutrient medium. 25) This is a very interesting finding because it suggests that changing the composition of the nutrient medium resulted in a change in the ECM components. We would like to perform detailed studies in this area in the future.…”

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

“…On the other hand, it may also be possible to improve hydrocarbon recovery from algal cells by preventing the production of the water-soluble polymer itself. In recent studies, hydrocarbon recovery was improved by changing the composition of the medium (Furuhashi et al 2013). It is interesting that carbohydrate metabolism seems to contribute to the recovery of hydrocarbons.…”

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

“…The hydrocarbon contents of the Showa strain cultured in freshwater medium (Chu 13 medium) and brackish medium (0.7% SM) were 34.3% and 35.5%, respectively. The difference in culture medium did not significantly affect the hydrocarbon content as was found in our previous study [20]. Hydrocarbon extractabilities after the two treatments-pre-heating (PH) and culture in brackish medium (CB)-were compared with that of no treatments (NT), that is, direct extraction from wet alga cultured in Chu 13.…”

“…Two types of culture media were used. One was modified Chu 13 medium as freshwater medium [20], and the other was a brackish medium with a salinity of 7 g•L -1 (0.7% SM) that was prepared by diluting commercial artificial seawater (Daigo's Artificial Seawater SP for Marine Microalgae Medium; Wako Pure Chemical Industries; total salinity, 36 g•L -1 ). Nutrients and trace metals, KNO 3, K 2 HPO 4…”

“…Although the algal biomass could be dried before extraction, a large amount of thermal energy was required for this process [17]. The extraction rate of hydrocarbons could be improved without requiring the drying of microalgae by pre-heating wet B. braunii or by culturing it in brackish medium [18][19][20].…”