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The biofuel potential of the green colonial microalga Botryococcus braunii
Abstract
Ever since the 1970's algae have been proposed as a source of oils for transportation fuel production, and this interest has been renewed in recent years. Algae fix CO2 very efficiently and are capable of producing large amounts of oils that can be used for combustion engine fuel production. The freshwater green alga Botryococcus braunii produces long-chain liquid hydrocarbon oils in large quantities that can be converted into petroleum-equivalent fuels suitable for combustion engines. Additionally, B. braunii hydrocarbon oils have been found as major constituents of currently used petroleum and coal deposits. Recently, genes and enzymes for the biosynthesis of B. braunii oils known as botryococcenes have been identified, and many studies have assayed different culture conditions for effectively growing B. braunii. Business evaluations of a B. braunii oil production system suggest that it may become competitive in the fuel market by the midtwenty- first century. This chapter summarizes current knowledge on the biosynthesis, biochemistry and molecular biology, as well as cost analysis of hydrocarbon production in B. braunii.
... In the USA: regular (97 RON) and premium (95 RON). Adapted from [16][17][18]. ...
... Characteristic alkadienes and alkatrienes of race A have double links and similar stereochemistry as oleic acid. Experiments with labeled fatty acids have shown that this one is the main precursor by the long-chain fatty acids (LCFAs) pathway, followed by a decarboxylation process [1,17,28,29]. The first step is the elongation of oleic acid (18:1 cis-Δ9) and its isomer elaidic acid (18:1 trans-Δ9). ...
... The first step is the elongation of oleic acid (18:1 cis-Δ9) and its isomer elaidic acid (18:1 trans-Δ9). The acyl-CoA reductase and decarbonylase enzymes in race A microsomes suggest an alternative mechanism where the LCFAs are reduced to aldehydes and decarbonylated to produce alkadienes and alkatrienes [17,30]. Race A transcriptome allowed the identification of six candidate genes potentially involved in this biosynthesis [31]. ...
... Using the optimal concentration of stress inducers determined above, the average hydrocarbon and biomass production of the treated B. braunii colonies was calculated after analysis every 24 h for 7 days after the treatments. Table 2shows those averages where the hydrocarbon content of non-treated cells was 31.91 ± 6.77% with a biomass productivity of 0.047 ± 0.009 g DW L −1 day −1 , which is similar to other reports (Cornejo-Corona et al., 2015). No significant differences in hydrocarbon or biomass productivity were observed in treated cells compared to the control except for the acetic acid treatment, which showed increased hydrocarbon production over the control (Table 2). ...
Plants react to biotic and abiotic stresses with a variety of responses including the production of reactive oxygen species (ROS), which may result in programmed cell death (PCD). The mechanisms underlying ROS production and PCD have not been well studied in microalgae. Here, we analyzed ROS accumulation, biomass accumulation, and hydrocarbon production in the colony-forming green microalga Botryococcus braunii in response to several stress inducers such as NaCl, NaHCO 3 , salicylic acid (SA), methyl jasmonate, and acetic acid. We also identified and cloned a single cDNA for the B. braunii ortholog of the Arabidopsis gene defender against cell death 1 ( DAD1 ) , a gene that is directly involved in PCD regulation. The function of B. braunii DAD1 was assessed by a complementation assay of the yeast knockout line of the DAD1 ortholog, oligosaccharyl transferase 2. Additionally, we found that DAD1 transcription was induced in response to SA at short times. These results suggest that B. braunii responds to stresses by mechanisms similar to those in land plants and other organisms.
Successful production of mixotrophic algae allows the integration of both photosynthetic and heterotrophic components during the diurnal cycle. This reduces the impact of biomass loss during dark respiration and decreases the amount of organic substances utilization during growth; these features infer that mixotrophic production can be an important part of the microalgae to biofuels process. Mixotrophic mode provides an effective way to cultivate Botryococcus braunii with high cell density and short cultivation cycle because exogenous carbon sources, in especial, organic carbon sources, such as sodium acetate, glucose and sucrose can stimulate the biomass production of the alga remarkably. The biomass and hydrocarbon volumetric productivities were promoted significantly by the mixotrophic cultivation of B. braunii compared with the photoautotrophic group, even though the hydrocarbon contents under mixotrophic conditions were not increased in pace with the biomass contents. The present study suggested that coupling the cultivation of mixotrophic microalgae and organic wastewater treatment is a potential way to produce microalgae biomass, accumulate hydrocarbon and remove organic and inorganic salts.
The use of microalgae in the skin care market is already established although the scientific rationale for their benefit was not clearly defined. In this work, the biological activities of dermatologic interest of the water extract from the microalga Botryococcus braunii (BBWE) were evaluated by a battery of in vitro assays. At concentrations ranging from 0.1 to 0.001 % (w/v) BBWE promoted adipocytes differentiation by inhibiting hormone-sensitive lipase, thus promoting triglyceride accumulation in the cells. BBWE also induced gene expression of proteins involved in the maintenance of skin cells water balance such as aquaporin-3 (AQP3), filaggrin (FLG) and involucrin (INV). 0.1 % BBWE increased the gene expression of AQP3 of 2.6-folds, that of FLG and INV of 1.5- and 1.9-folds, respectively. Moreover, it induced the biosynthesis of collagen I and collagen III by 80 and 40 %, respectively, compared to the untreated control. BBWE antioxidant activity, evaluated by oxygen radical absorbance capacity (ORAC) assay, was of 43.5 μmol Trolox per gram of extract: a quite high value among those found for other microalgae extracts. BBWE inhibited the inducible nitric oxide synthase (iNOS) gene expression and the consequent nitrite oxide (NO) production under oxidative stress. At a concentration of 0.02 % BBWE reduced by 50 % the expression of iNOS and by about 75 % the NO production. Taken together, the results demonstrated that B. braunii water extract exerted an array of biological activities concurring with the skin health maintenance; therefore, it is a potential bioactive ingredient to be included in cosmetic products.