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

Abstract

The green colonial microalga Botryococcus braunii (race B) has attracted considerable attention because it is known to produce many hydrocarbons. The hydrocarbons are present in the extracellular matrix that connects the cells located in the interior of a B. braunii colony; however, the surface of each colony is covered with a retaining wall and a fibrillar colony sheath. This unique colony structure is thought to be associated with hydrocarbon storage and known to affect the extractability of hydrocarbons by using an organic solvent. In this study, we investigated the relation between hydrocarbon extractability and changes in the colony surface structure after two distinct treatments: culture of the algae in brackish medium or thermal pretreatment of the algae before solvent extraction. Both the treatments improved hydrocarbon extractability when non-polar solvents such as n-hexane were used. Thermal pretreatment inhibited the formation of fibrils on the surface of algal colonies, as revealed by rapid-freezing and freeze-substitution electron microscopy. However, when the alga was cultured in brackish medium, the fibrils on the surface shortened and became less dense. Thus, the fibrillar colony sheath that mainly consisted of saccharic components prevented the entry of organic solvents into the colony interior, and thus hydrocarbon extraction.

Non-invasive magnetic resonance imaging of oils in Botryococcus braunii green algae: Chemical shift selective and diffusion-weighted imaging

“…It is likely caused by diffusion mediated interactions between the surrounding medium and the exopolysaccharide fibrillary sheath of B . braunii [ 28 , 29 ].…”

In situ extraction (milking) of the two promising Botryococcus braunii strains Showa and Bot22 under optimized extraction time

“…2). This compact arrangement of the cells in the colonies of strain Showa probably results in a higher resistance to negative environmental influences (Furuhashi et al 2016b). This could explain the different optimal extraction times of the two strains, as well as a longer extraction time required for strain Showa, which consists of more compact colonies, to cause a negative effect of the solvent, compared to strain Bot22 with a looser colony structure.…”

Synthetic Biology-derived triterpenes as efficacious immunomodulating adjuvants

“…Botryococcene is naturally produced only by the green algae, Botryococcus braunii , which has specific races; one of which (race B) produces large amounts of triterpene oils, including methylated forms of both squalene and botryococcene 26 , 28 . While B. braunii can produce large amounts of triterpene oil (> 30% of its dry weight) its slow-growth habit 29 , resistance to extraction 30 , and mixture of chemically similar triterpene oils—which would require laborious purification to obtain large amounts of individually pure triterpenes—all make it a less desirable source. Yeast have several advantages such as ease of genetic modification, a large body of work in scaling bioreactor/fermentation processes, a prevalence of accessible infrastructure for scaling, and are a g enerally r ecognized a s s afe (GRAS) organism by the FDA 31 .…”