GROWTH AND BRANCHED HYDROCARBON PRODUCTION IN A STRAIN OF BOTRYOCOCCUS BRAUNII (CHLOROPHYTA)¹

Abstract

A strain Botryococcus braunii Kütz. that produces high levels of branched hydrocarbons (botryococcenes) was grown under different environmental conditions to investigate the relationship between growth and hydrocarbon production. Carbon dioxide concentration had the most significant influence on growth; 0.3% CO2‐enriched cultures demonstrated a minimum mass doubling time of ca. 40 h, compared to ca. 6 days for ambient air cultures grown on the same buffered growth medium. The botryococcene fraction, which consisted of 10 identified compounds (CnH2n‐10; n = 30–34), usually constituted ca. 25–40% of the culture dry weight under various growth regimes, including nitrogen‐ and/or phosphate‐deficiencies. CO2 enrichment initially favored the production of the lower botryococcenes (C30–C32), whereas relatively slow‐growing ambient air cultures accumulated C33 and C34 compounds. Colony color changed in response to different light intensities. High light increased the carotenoid/chlorophyll ratio, which resulted in orange colonies. Cultures exposed to low light intensity appeared green. This change in coloration was reversible over a period of a few days, and at no time were the linear hydrocarbons characteristic of the other form of the alga detected. Ostensible colony color is not, therefore, a reliable indicator of qualitative hydrocarbon content. Sequential solvent extraction experiments indicated that up to ca. 7% of the botryococcene fraction was intracellular and that the remainder was located within the colonial matrix. The internal (cellular) pool principally consisted of C30–C32 botryococcenes, whereas the external (colonial matrix) pool contained >99% of the C33 and C34 compounds, in addition to large amounts of the lower botryococcenes. These results, taken in conjunction with other data, are compatible with the hypothesis that the C30 botryococcene is the precursor, presumably via methylation, of the higher botryococcenes.

Wavelength specificity of growth, photosynthesis, and hydrocarbon production in the oil-producing green alga Botryococcus braunii

“…The color of red light-grown cells changed to yellow during the 6 months that the cells were maintained under monochromatic illumination (data not shown). This change seemed to be due to an increase in the ratio of carotenes/chlorophyll content, based on the absorption spectrum of the 90% methanol extracts, as previously reported in the cyanobacteria Synechococcus and Prochlorococcus (Moore et al, 1995) and B. braunii during light-acclimating processes (Wolf et al, 1985). In contrast, the photosystem activity parameters such as Fv/Fm, qP, φII, and NPQ showed no difference among the blue, green, and red light-grown cells (Fig.…”

“…An oil-producing green alga Botryococcus braunii is a promising renewable source of petroleum substitute, as it produces hydrocarbons by fixing atmospheric CO 2 photosynthetically (Banerjee et al, 2002;Casadevall et al, 1985;Largesu et al, 1980;Metzger and Largeau, 2005;Wolf et al, 1985).…”

Liquid Fuel Production Using Microalgae

“…It was reported that B. braunii Berkeley-strain grew at 1.2 g/l per week with continuous light (250 µE/m 2 /s) and 23-25°C 4) . A higher STS supply rate could cause an increase in the algal growth rate in the continuous system.…”

Raman Spectroscopy Analysis of Botryococcene Hydrocarbons from the Green Microalga Botryococcus braunii

“…Once produced, C 30 botryococcene is further metabolized by methylation at carbons 3, 7, 16, and 20 to produce C 31 , C 32 , C 33 , and C 34 botryococcenes (19,43,44), and even further methylated to C 36 and C 37 botryococcenes in some B race strains (22,45). In C 34 botryococcene-producing strains such as the Berkeley (Showa) strain, the majority (Ͼ99%) of the C 34 botryococcenes exist in the extracellular matrix whereas the intracellular oil comprises predominantly the lower carbon number botryococcenes (19,20). These botryococcenes are excreted to the extracellular matrix as they mature to C 34 botryococcene (19,20).…”