Why Sequence Botryococcus braunii?

Botryococcus braunii is a colony-forming green microalga of the species Chlorophyceae. It is found in many environments across the globe and has been noted to be capable of growing in both freshwater and brackish environments. During the growth cycle of this organism, the algae synthesize long-chain liquid hydrocarbon compounds and sequester them in the extracellular matrix of the colony to afford buoyancy. (Typical hydrocarbon content of the organism is approximately 30-40% of the dry weight of the cells.) Three phenotypically distinct isolates, or “races,” of B. braunii have been reported (races A, B, and L). These races are identified by the type of oil produced and accumulated by the organism. Of the three, the oils produced by race B, a family of isoprenoid compounds termed botryococcenes, hold the most promise as an alternative energy source. Botryococcenes have been converted to fuel suitable for internal combustion engines through caustic hydrolysis, and geochemical analysis has shown that botryococcenes, presumably from ancient B. braunii communities, also compose a portion of the hydrocarbon masses in several modern-day petroleum and coal deposits.

Algae are already recognized as a promising carbon sequestration agent. Moreover, the hydrocarbons produced by B. braunii hold significant promise as a renewable biofuel. Despite this, little information, either genetic or metabolic, has been reported for this organism. For instance, the identities of the exact genes in the metabolic pathway responsible for hydrocarbon synthesis have been elusive. This knowledge is sorely needed for any efforts to identify and alleviate bottlenecks in metabolic flux through this pathway and thus enable its use as a source of biofuels.

Principal Investigators: Andrew Koppisch (Los Alamos Natl. Lab. and Northern Arizona Univ), Hakim Boukhalfa, Christy Ruggiero, David T. Fox, and Nathan M. Beck (Los Alamos Natl. Lab.); Suraj Dhungana (Natl. Inst. of Environmnetal Health Sciences, Durham NC); Joseph Chappell (Univ. of Kentucky); Timothy P.
Devarenne (Texas A&M Univ.); Shigeru Okada (Tokyo Univ.); C. Dale Poulter (Univ. of Utah); and Rolf J. Mehlhorn, Jill O. Fuss, and Anastasios Melis (Lawrence Berkeley
Natl. Lab.).

Program: CSP 2009