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Botryococcus braunii

Botryococcus braunii is a colonial green microalga belonging to the class Trebouxiophyceae in the division Chlorophyta, characterized by its unicellular, oval-shaped cells that aggregate into macroscopic, gelatinous colonies via a complex extracellular matrix.^[1]^[2] It is renowned for synthesizing and secreting large quantities of liquid hydrocarbons extracellularly, which can constitute 25–75% of its dry biomass, distinguishing it from most microalgae that store lipids intracellularly.^[2] These hydrocarbons serve as energy reserves and contribute to the alga's buoyancy and colonial structure.^[3] A 2024 comparative genomics study reclassified what were previously considered chemical races of B. braunii into distinct species, with B. braunii corresponding to the former race B, which generates C₃₀–C₃₇ botryococcenes and related triterpenoids. Related species include Botryococcus alkenealis (formerly race A, yielding odd-numbered C₂₅–C₃₁ n-alkadienes and alkatrienes) and Botryococcus lycopadienes (formerly race L, biosynthesizing the tetraterpenoid lycopadiene (C₄₀)).^[3]^[2]^[4] A fourth type, formerly race S and producing saturated hydrocarbons, has been described but is less common.^[2] Colony color varies from green during active growth to reddish or yellowish in stationary phases, influenced by carotenoid accumulation.^[3] B. braunii inhabits freshwater and brackish lakes, ponds, and reservoirs across temperate to tropical regions worldwide, functioning as a cosmopolitan planktonic species that typically maintains low densities (10–10² colonies per liter) but can form blooms in nutrient-enriched waters.^[2] Ecologically, it interacts with bacterial symbionts and faces competition from other phytoplankton, though details of its life cycle, including reproduction and dormancy, remain poorly understood.^[2] Its fossilized remains are prevalent in ancient oil shales and petroleum source rocks, underscoring its historical role in hydrocarbon deposition.^[2] Due to its exceptional hydrocarbon yield, B. braunii holds significant promise as a renewable feedstock for biofuels, with hydrocarbons convertible to gasoline, diesel, and jet fuel via processes like hydrocracking.^[3]^[2] Research focuses on optimizing cultivation in photobioreactors or open ponds, enhancing production through nutrient manipulation (e.g., cobalt supplementation), and developing extraction techniques to harness its lipids (up to 55% dry weight) alongside hydrocarbons.^[3] This positions it as a sustainable alternative to fossil fuels, capable of CO₂ sequestration during growth.^[3]

Taxonomy and Morphology

Classification

Botryococcus braunii is classified within the domain Eukaryota, kingdom Viridiplantae, phylum Chlorophyta, class Trebouxiophyceae, order Trebouxiales, family Botryococcaceae, genus Botryococcus, and species braunii.^[5]^[1] This placement reflects an update from earlier assignments to the class Chlorophyceae, driven by molecular phylogenetic analyses that repositioned the genus within the Trebouxiophyceae based on small subunit ribosomal RNA (18S rRNA) gene sequences. The genus Botryococcus was established by Friedrich Traugott Kützing in 1849, with B. braunii designated as the type species.^[6] The genus currently encompasses 13 accepted species, characterized by their colonial growth forming grape-like aggregates. The name Botryococcus derives from the Greek "botrys," meaning a cluster of grapes, alluding to the organism's distinctive colonial morphology.^[7] Historically, B. braunii has undergone reclassifications, including shifts in familial and ordinal assignments as algal taxonomy evolved from morphological to molecular criteria. No synonyms are formally recognized for B. braunii itself, though recent comparative genomics has prompted the reclassification of its chemical races—A, B, and L—into distinct species: race B retains the name Botryococcus braunii, while race A is now Botryococcus alkenealis and race L is Botryococcus lycopadienealis.^[4] Phylogenetically, B. braunii clusters within the Trebouxiophyceae, showing close affinity to Chlorella-like lineages such as Choricystis based on analyses of 18S rRNA and internal transcribed spacer (ITS) sequences, which highlight its position in a monophyletic group distinct from other green algal classes.^[8]

Physical Characteristics

_Botryococcus braunii is classified within the Trebouxiophyceae, a class of green algae characterized by its colonial habit. Individual cells are typically pyramid-shaped or spherical, measuring 10-25 μm in diameter. The cell wall is composed of a resistant biopolymer resembling sporopollenin, which provides structural integrity and chemical resistance.^[9]^[6]^[10] The alga exhibits a distinctive colonial organization, with non-motile cells embedded in an extracellular matrix that forms dense clusters known as botryoids, which can reach macroscopic sizes up to several millimeters in diameter. This matrix, rich in polysaccharides and hydrocarbons, encases groups of 50-100 cells, creating a cohesive, grape-like structure that aids in buoyancy and protection.^[11]^[6]^[10] Reproduction primarily occurs asexually through the formation of autospores, where daughter cells develop within the mother cell and retain its wall, resulting in layered, multi-walled structures that accumulate over successive divisions. Evidence from genomic analysis, including meiosis-specific genes, suggests potential for sexual reproduction, inferred from observed genetic diversity, although zygote formation has not been directly documented.^[12]

Habitat and Ecology

Natural Distribution

Botryococcus braunii is widely distributed in temperate and tropical regions, primarily inhabiting freshwater lakes, ponds, and reservoirs across most continents except Antarctica. It also occurs in brackish waters with salinities up to 10-15 parts per thousand (ppt), demonstrating tolerance to mildly saline conditions in estuaries and coastal lagoons. This alga thrives in stagnant or low-flow environments where nutrient availability is elevated, such as eutrophic systems, but forms sporadic blooms rather than consistent global populations, with no comprehensive abundance data available due to its patchy occurrence.^[13]^[14]^[15] Notable natural populations include race B strains in Australian freshwater bodies, ranging from tropical to temperate zones, such as billabongs and ponds. Race A strains are commonly found in Japanese lakes and ponds, including sites in Miyagi, Fukui, and Kochi prefectures. In Europe, race L strains have been documented in Portuguese reservoirs, while African wetlands in countries like Namibia, South Africa, and Mozambique host diverse populations. Asian wetlands, including those in Indonesia (e.g., Palangka Raya and Bunto) and the Philippines (e.g., Paoay Lake), also support blooms, often in nutrient-rich, low-flow settings.^[16]^[17]^[18]^[19]^[20] The alga exhibits seasonal prevalence in eutrophic waters during warmer months, typically spring and summer, when temperatures and nutrient levels favor bloom formation. Historical records date back to 19th-century European collections, with initial descriptions from German botanist Friedrich Traugott Kützing in 1845 based on samples from continental waters. These populations are promoted by conditions like minimal water flow and high nutrient loads from surrounding watersheds, though blooms remain unpredictable and localized.^[20]^[21]

Growth Conditions

Botryococcus braunii exhibits optimal growth at temperatures between 20°C and 30°C, with maximum biomass productivity observed around 25°C for most strains. Growth is inhibited below 10°C, where cellular division ceases or slows dramatically, and above 35°C, leading to reduced viability and photosynthetic efficiency.^[22]^[23] The alga thrives in a pH range of 6.5 to 9.0, showing preference for neutral to slightly alkaline conditions that support stable colony formation and nutrient uptake. Nutrient needs are moderate, requiring nitrogen at 0.5–2 g/L as nitrate (e.g., via NaNO₃ in standard media like modified Chu 13), phosphorus at 0.05–0.2 g/L (e.g., from K₂HPO₄), and essential trace metals such as iron, manganese, and molybdenum for enzymatic functions in photosynthesis and hydrocarbon synthesis. For phototrophic growth, light intensities of 50–200 μmol photons m⁻² s⁻¹ promote balanced biomass accumulation without photoinhibition, though higher levels can stress cells in dense cultures.^[24]^[25]^[3] B. braunii displays a characteristically slow growth rate, with doubling times ranging from 3 to 7 days under standard conditions, limiting its scalability compared to faster microalgae. However, mixotrophic cultivation using glucose supplementation (typically 5–20 mM) enhances biomass productivity by 2–3 fold relative to phototrophy alone, by providing an alternative carbon source that accelerates cell division and colony expansion. Recent studies from 2025 have explored CO₂ enrichment up to 5% in photobioreactors, which boosts growth rates and biomass yields by improving carbon fixation efficiency, often combined with LED lighting optimized for blue and red wavelengths to minimize energy costs and enhance photosynthetic performance.^[25]^[26]^[27]

Ecological Interactions

Botryococcus braunii forms dense blooms in stagnant freshwater environments, such as lakes and reservoirs, where it creates thick green or reddish mats that cover water surfaces and can reach biomass levels of up to 1500 tons in a single event. These blooms often occur in nutrient-enriched, low-flow conditions, leading to surface scums that alter light penetration and contribute to localized hypoxic zones by increasing organic matter decomposition. In man-made lakes like those in Sarawak, Malaysia, such proliferations have been documented to dominate the phytoplankton community, comprising over 90% of algal biomass during peak periods.^[28]^[29]^[19] In aquatic ecosystems, B. braunii engages in competitive interactions with other microalgae, including diatoms and cyanobacteria, primarily through allelopathic effects mediated by excreted hydrocarbons and free fatty acids that inhibit competitor growth and reduce phytoplankton diversity. This chemical defense enables B. braunii to maintain dominance in mixed assemblages, as observed in natural blooms where its presence suppresses surrounding algal populations. Additionally, the alga's robust extracellular matrix, rich in polysaccharides and hydrocarbons, confers physical resistance to grazing by zooplankton such as Daphnia, thereby limiting predation and enhancing colony survival despite the matrix's vulnerability to certain enzymatic breakdown.^[30]^[31]^[19]^[32] B. braunii often associates with bacterial ectosymbionts, such as alphaproteobacteria, which attach to the extracellular matrix and promote algal growth by enhancing nutrient uptake and biomass productivity, contributing to its ecological success in natural environments.^[33] Hydrocarbon exudates from B. braunii blooms pose potential toxicity risks to aquatic biota, particularly inhibiting zooplankton motility and fish respiration through cytotoxic effects of free fatty acids. Documented impacts include mass fish mortalities linked to blooms in Australian reservoirs like the Darwin River in the 1970s, as well as water quality degradation and zooplankton suppression in Taiwanese, Malaysian, and Philippine lakes during the 2000s and 2010s. These events highlight how bloom-derived allelochemicals can disrupt food webs and exacerbate environmental stress in affected water bodies.^[34]^[35]^[29]^[28]^[20] Beyond immediate ecological disruptions, B. braunii contributes to carbon sequestration by fixing atmospheric CO₂ during rapid bloom growth and facilitating long-term burial of organic carbon in sediments, where its hydrocarbon-rich biomass resists decomposition. Fossilized colonies of the alga serve as key paleo-indicators in ancient oil shales, with biomarkers like botryococcane revealing past freshwater depositional environments from the Precambrian onward and contributing up to 90% of organic matter in some Eocene formations. This sedimentary legacy underscores B. braunii's historical role in global carbon cycling and paleoclimate reconstruction.^[36]^[37]^[38]^[39]

Biochemistry and Physiology

Hydrocarbon Biosynthesis

Botryococcus braunii accumulates hydrocarbons representing up to 75% of its dry cell weight, primarily within lipid bodies located in the extracellular matrix surrounding the cells rather than in the cytoplasm. This extracellular deposition, which can constitute over 90% of the total hydrocarbons, facilitates the formation of a colonial structure and protects the cells from environmental stress. The lipid bodies, composed mainly of neutral lipids including triacylglycerols and hydrocarbons, are synthesized intracellularly and then transported to the matrix via mechanisms involving ABC transporters.^[2]^[11]^[40] The biosynthetic pathways for hydrocarbons in B. braunii vary by race. In race A, odd-numbered alkadienes and alkatrienes (C₂₃–C₃₃) are derived from fatty acids synthesized via the fatty acid synthase complex, starting with acetyl-CoA carboxylase catalyzing the carboxylation of acetyl-CoA to malonyl-CoA, followed by chain elongation and subsequent decarboxylation and reduction steps to form the terminal alkene groups. In contrast, race B produces triterpenoid botryococcenes (C₃₀–C₃₇) primarily through the mevalonate-independent (MEP/DXP) pathway in the cytosol, where farnesyl pyrophosphate units are condensed by squalene synthase-like enzymes to form squalene precursors, which are then cyclized and methylated. Race L utilizes a modified squalene synthase for tetraterpenoid lycopadiene (C₄₀) production from geranylgeranyl diphosphate. These pathways highlight the alga's versatility in hydrocarbon production, with transcriptomic studies identifying key enzyme-encoding genes such as those for squalene synthase isoforms.^[41]^[42]^[43]^[10] Hydrocarbon biosynthesis is regulated by environmental cues, notably nitrogen limitation and high light intensity, which induce oleaginicity by redirecting carbon flux toward lipid accumulation. Under nitrogen deprivation, hydrocarbon content can increase up to 2.8-fold, accompanied by downregulation of photosynthetic genes and upregulation of carbohydrate metabolism pathways, as revealed by de novo transcriptomics. Recent studies from 2015 to 2018 using RNA-seq on strains like UTEX 572 (race A) and Showa (race B) have identified genetic loci, including squalene synthase upregulation in race B under stress, enabling enhanced triterpenoid synthesis. High light further boosts photosynthetic electron transport, favoring NADPH production for biosynthesis.^[44]^[45]^[40] The energy balance for hydrocarbon synthesis in B. braunii relies on photosynthesis, with overall efficiency typically ranging from 1-2% for converting solar energy to biomass, constrained by self-shading in colonies. Metabolic models indicate that fatty acid-derived hydrocarbons in race A require approximately 1 ATP and 2 NADPH per two-carbon elongation unit, plus additional reducing power for decarboxylation. For triterpenoids in race B, the mevalonate-independent pathway demands high ATP and NADPH inputs for isoprenoid precursor formation, with each C5 unit needing 1 ATP, 1 CTP, and multiple reducing equivalents, underscoring the high energetic cost that limits growth rates but enables high hydrocarbon yields.^[43]^[46]

Races and Oil Composition

As of 2024, the chemical races of Botryococcus braunii have been reclassified as distinct species based on genomic analyses: race A as Botryococcus alkenealis, race B as Botryococcus braunii, and race L as Botryococcus lycopadienor.^[4] These races (or species) exhibit distinct biochemical profiles that influence their potential applications, particularly in biofuel production. Race A predominantly synthesizes odd-numbered alkadienes and trienes ranging from C₂₃ to C₃₃, such as botryals, which constitute up to 10% of the dry cell weight. These hydrocarbons are derived from fatty acid precursors through processes like chain elongation and decarboxylation.^[10] Race B is characterized by high levels of triterpenoid hydrocarbons, including botryococcenes (C₃₀–C₃₇), accounting for 25-75% of the dry cell weight. These compounds are synthesized via the mevalonate-independent isoprenoid pathway, making race B the most extensively studied for biofuel prospects due to its substantial oil accumulation. In contrast, race L produces the tetraterpenoid lycopadiene (C₄₀), with intermediate yields typically ranging from 2-10% of dry weight. A fourth race, S, has been proposed but is less common and not fully accepted, producing saturated hydrocarbons such as n-alkanes (C₁₈, C₂₀).^[10]^[47]^[10] Comparatively, race B hydrocarbons exhibit the highest energy density at approximately 45 MJ/kg, surpassing typical diesel fuel values and highlighting their suitability as drop-in biofuels. The overall oil composition across races includes minor components such as fatty acids (10-20% of total lipids, primarily palmitic and oleic acids) and sterols, which contribute to structural integrity but are secondary to the dominant hydrocarbons. Identification and quantification of these components rely on analytical techniques like gas chromatography-mass spectrometry (GC-MS), which resolves the complex mixtures based on molecular weight and fragmentation patterns. While the hydrocarbon biosynthesis pathways differ by race—as detailed in the hydrocarbon biosynthesis section—race B's triterpenoids provide the most promising profile for high-yield energy applications.^[48]^[10]

Biotechnological Applications

Biofuel Production

B. braunii lipids show significant potential as feedstocks for biodiesel, convertible via direct transesterification using sulfuric acid and methanol, yielding fatty acid methyl esters suitable for diesel engines.^[49] Race B botryococcenes, triterpenoid hydrocarbons, can undergo hydrocracking to produce gasoline-range or aviation fuel-range alkanes, with processes achieving up to 52% yield of C10–C15 fractions at 300°C using NiMo/Al2O3 catalysts.^[50] These converted products exhibit properties suitable for diesel and aviation applications.^[51] Key advantages include the high hydrogen-to-carbon (H/C) ratio of botryococcenes (approximately 1.7–1.8), comparable to petroleum-derived fuels, enabling efficient energy density without the land-use conflicts of food crops, as B. braunii is a non-food algal species.^[52] In optimized photobioreactor or raceway pond systems, projected biomass yields reach 5–15 tons per hectare per year, supporting scalable hydrocarbon production for biofuels.^[53] Despite these benefits, challenges persist, primarily the slow growth rate of B. braunii (doubling time 5–7 days), which limits biomass accumulation and commercial scalability compared to faster-growing microalgae.^[3] Recent economic analyses indicate break-even production costs of approximately $3.20 per liter for hydrocracked fuels without subsidies, driven by high cultivation and harvesting expenses, though optimizations could reduce this to $1.45 per liter.^[54] To address costs, integration with wastewater treatment provides nutrient-rich media, enhancing growth while remediating effluents, as demonstrated in studies.^[55] Utilizing flue gas CO₂ as a carbon source further boosts productivity under high concentrations (up to 15% CO₂), with B. braunii tolerant to levels as high as 50% in lab conditions.^[56] Recent studies (as of 2024) have explored radiation mutagenesis (gamma and UV) to enhance biomass and hydrocarbon yields, achieving improved biodiesel properties.^[57] The oil compositions, particularly race B botryococcenes suitable for these fuels, are detailed in the Races and Oil Composition section.

Oil Extraction Techniques

Botryococcus braunii's hydrocarbons, primarily extracellular in races A and B such as botryococcenes and lycopadiene, lend themselves to extraction techniques that either preserve or disrupt the colonial structure for recovery. Non-destructive methods, often termed "milking," selectively target these external oils using biocompatible solvents like n-hexane or n-heptane, allowing repeated harvesting without cell lysis and enabling biomass regrowth.^[58] In these processes, cultures are agitated with solvent for 1-2 hours every 5-11 days, achieving yields of 12-17 mg/L/day over 30-80 days, with race B strains like Showa demonstrating up to 16.99 mg/L/day under optimized CO₂ supplementation.^[58] Mechanical blotting applies low pressure (215-875 Pa) to squeeze out oils, recovering about 1-35% of total hydrocarbons with heptane assistance, followed by a 6-day recovery period where cells resume growth and photosynthesis without significant impairment (Fv/Fm ratios stable).^[58] These approaches minimize energy costs and support continuous cultivation, though solvent toxicity must be managed to avoid growth inhibition.^[58] Recent advances (as of 2025) include milking with squalane solvent for simultaneous culture and recovery.^[59] Destructive extraction techniques involve cell disruption to access both extracellular and intracellular lipids, typically followed by solvent or advanced fluid extraction, yielding higher overall recoveries of 70-90% from dry biomass. Ultrasonication applies high-frequency waves (20-40 kHz) for 10-30 minutes to rupture cell walls, enhancing solvent penetration and increasing lipid yields by 20-50% compared to untreated controls when combined with hexane.^[60] Microwave-assisted disruption heats biomass to 45-60°C for 15 minutes, boosting oil extraction to 37.6% via the Bligh & Dyer method, outperforming bead milling or ultrasound alone by facilitating rapid cell permeabilization without excessive degradation.^[61] Enzymatic hydrolysis employs enzymes like manganese peroxidase (1000 U/L) to degrade the polysaccharide-rich cell wall over 24-72 hours at mild temperatures (30-40°C), achieving up to 85% hydrolysis and improving downstream lipid accessibility by 62% relative to untreated algae.^[62] Supercritical CO₂ extraction, conducted at 40°C and 20-30 MPa, selectively recovers hydrocarbons (up to 37% of total lipids) in a solvent-free manner, with yields rising proportionally to pressure due to the non-polar nature of botryococcenes.^[63] Recent advances include pulsed electric field (PEF) treatment at 20-65 kV/cm, which permeabilizes cells for 50-80% hydrocarbon release while preserving 25% viability for potential hybrid processes, and CO₂-switchable solvents like N,N-dimethylcyclohexylamine that toggle solubility at 60-80°C for 22% dry weight yields with reduced environmental impact.^[58] Post-extraction, biomass separation employs centrifugation (3000-5000 g) or air flotation to recover spent cells, while distillation under vacuum removes impurities like residual solvents or pigments, purifying hydrocarbons to >95% for further applications.^[64] These steps ensure high-purity outputs, though optimization for race-specific compositions remains key to maximizing efficiency.^[63]

Research and Strains

Historical and Recent Studies

Botryococcus braunii was first described in 1849 by Friedrich Traugott Kützing as a colonial green alga found in freshwater environments.^[1] Early observations noted its distinctive colony-forming structure, but its potential as a hydrocarbon producer was not recognized until the late 1960s. In 1968, Maxwell and colleagues used nuclear magnetic resonance (NMR) spectroscopy to identify unusual botryococcene hydrocarbons in field-collected samples, marking the initial documentation of its oil-rich composition and sparking interest in its biochemical uniqueness.^[65] During the 1980s and 1990s, research focused on classifying B. braunii into chemical races based on hydrocarbon types. This period saw the identification of races A, B, and L, distinguished by alkadiene/alkatriene production in race A, botryococcenes in race B, and lycopadiene in race L. By the early 2000s, genetic studies provided initial insights into its phylogeny and genome, with Metzger and Largeau's 2005 review synthesizing ether lipid and hydrocarbon pathways, highlighting evolutionary adaptations for oil accumulation. In the 2010s, advances in omics technologies deepened understanding of its physiology. Transcriptome analyses, such as the 2018 comparative study by Kageyama et al. on race A under cobalt enrichment, revealed upregulated genes in fatty acid and terpenoid biosynthesis pathways, identifying key enzymes like acyl-ACP thioesterase for hydrocarbon production.^[45] Genetic engineering efforts emerged, with draft genome sequences for race B in 2017 enabling targeted modifications, though challenges persisted due to its colonial morphology.^[66] From 2023 to 2025, research emphasized sustainable cultivation amid energy transitions. A 2025 study in Science of the Total Environment explored integrated biorefinery approaches using bloom-forming B. braunii strains in wastewater treatment-integrated systems, achieving cell densities up to 3.3 × 10⁶ colonies L⁻¹ and highlighting potential biomass productivities supporting biofuel scalability.^[67] These developments underscore B. braunii's role in circular bioeconomies, with ongoing trials in co-cultivation systems to enhance yields and reduce environmental impacts.^[55] In 2024, a genomic analysis proposed reclassifying the chemical races A, B, and L as distinct species, refining taxonomic understanding for biotechnological applications.^[68] A 2025 study advanced non-destructive extraction via a squalane-based milking process, improving hydrocarbon recovery efficiency.^[59]

Promising Strains

Several strains of Botryococcus braunii have been identified as particularly promising for biotechnological applications, primarily due to their high hydrocarbon yields, extracellular production facilitating non-destructive extraction, and scalability in cultivation systems. These strains often belong to race B, which produces triterpenoid botryococcenes, offering higher hydrocarbon content (up to 50% of dry biomass) compared to race A strains (typically <25%). Selection criteria include biomass productivity, hydrocarbon composition, solvent compatibility for "milking" processes, and overall energy efficiency in extraction.^[69]^[70] The strain Bot22 (race B) stands out for its suitability in repetitive, non-destructive hydrocarbon extraction via the milking process, achieving a biomass density of 2.634 g L⁻¹ and hydrocarbon content of 51.6% of dry biomass, with a production rate of 68 mg L⁻¹ day⁻¹. Its extracellular hydrocarbons are highly compatible with solvents like n-octane, maintaining over 85% oxygen production post-extraction, which minimizes disruption to algal growth and reduces downstream processing costs. This makes Bot22 ideal for continuous biofuel production systems.^[69] Strain AC761 (race B) is noted for its botryococcene production (C₃₀–C₃₄ hydrocarbons) at 40–45% of dry biomass in bubble column reactors, demonstrating scalability for industrial applications such as aviation fuel precursors. It exhibits robust growth in photobioreactors, with hydrocarbon contents ranging from 5–42% under optimized conditions, enhancing overall yield.^[70]^[71] The Showa strain (race B) achieves one of the highest reported hydrocarbon contents at 42% of dry biomass in shake flasks and 25% in bubble columns, positioning it as a benchmark for high-density cultures aimed at liquid fuel production. Its consistent performance across cultivation scales underscores its potential for large-scale biofuel operations.^[70] A novel strain, GUBIOTJTBB1, shows exceptional lipid accumulation at 56.3% (w/w) of biomass, with 24.9% aliphatic hydrocarbons recoverable via wet process solvent extraction (WPSE), yielding up to 89% recovery efficiency without prior drying. This strain's in situ extraction compatibility addresses key harvesting challenges, making it promising for cost-effective hydrocarbon biofuels.^[72] For applications beyond hydrocarbons, strain CCALA778 excels in exopolysaccharide (EPS) production (>50% of dry biomass), which can be doubled via UVC treatment to mitigate bacterial antagonism, offering value in food and pharmaceutical sectors while complementing hydrocarbon-focused strains.^[71]

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Allelochemicals of Botryococcus braunii (Chlorophyceae)
Aug 7, 2025 · braunii's ability to chemically inhibit other zooplankton and algae by secreting inhibitory levels of free fatty acids into the medium (Chiang ...
[33]
Botryococcus braunii reduces algal grazing losses to Daphnia and ...
Aug 14, 2024 · Because the size of B. braunii colonies (up to 200 µm in diameter) is significantly greater than cell size of strains of industrial interest ...
[34]
Characteristics of extracellular hydrocarbon-rich microalga ...
... toxic effect on fish and zooplankton in the proximity of B. braunii blooms, mainly associated with either the well-known cytotoxic effects of free fatty ...
[35]
allelochemicals of botryococcus braunii (chlorophyceae)1
Because B. braunii is toxic to all the zooplankton tested in the present study, it seems possible that it is toxic to fish. However, an ...
[36]
Role of Microalgae in Global CO2 Sequestration - MDPI
Enhancement of biomass and hydrocarbon productivities of Botryococcus braunii by mixotrophic cultivation and its application in brewery wastewater treatment.
[37]
Palaeogenomics of the Hydrocarbon Producing Microalga ... - NIH
Feb 11, 2019 · Botryococcus appear early in the fossil record and are found globally in oil shales dating from the Precambrian (>542 Myr), where they are the ...Missing: paleoindicator | Show results with:paleoindicator
[38]
Palaeogenomics of the Hydrocarbon Producing Microalga ...
Botryococcus braunii is a colonial microalga that appears early in the fossil record and is a sensitive proxy of environmental and hydroclimatic conditions.
[39]
Biomarker evidence for Botryococcus and a methane cycle in the ...
Several of these shales were deposited in the Eocene, including the lacustrine Maoming oil shale that has been the subject of several biomarker studies (e.g. ...
[40]
Bio-crude transcriptomics: Gene discovery and metabolic network ...
Amongst oleaginous eukaryotic algae, the B race of Botryococcus braunii is unique in that it produces large amounts of liquid hydrocarbons of terpenoid origin.
[41]
Comparative transcriptome analyses of oleaginous Botryococcus ...
Dec 18, 2018 · Botryococcus braunii is known for its high hydrocarbon content, thus making it a strong candidate feedstock for biofuel production.
[42]
Identification of unique mechanisms for triterpene biosynthesis in ...
Botryococcene biosynthesis is thought to resemble that of squalene, a metabolite essential for sterol metabolism in all eukaryotes.Missing: upregulation nitrogen
[43]
Biosynthesis of Lipids and Hydrocarbons in Algae - IntechOpen
Jun 12, 2013 · In this chapter, we will introduce recent progresses on lipid and hydrocarbon biosynthetic pathways in microalgae.
[44]
Transcriptomic analysis of a moderately growing subisolate ...
Aug 28, 2015 · ... Botryococcus sp. CCALA-779 belongs to the A race B. braunii based on the results of 18S rRNA sequence-based phylogenetic analysis and GC–MS ...
[45]
Comparative transcriptome analyses of oleaginous Botryococcus ...
Dec 18, 2018 · Botryococcus braunii has three different races (A, B, L) based on the synthesized hydrocarbons. Race A produces fatty acid-derived C23–C33 ...Missing: Australia billabongs
[46]
Reducing self-shading effects in Botryococcus braunii cultures
Apr 26, 2021 · In this work we studied the effect of decreasing concentrations of Magnesium (Mg 2+ ) on the chlorophyll a content, photosynthetic performance, biomass and ...
[47]
https://doi.org/10.1080/07388550290789513
[48]
[PDF] Experimental investigation on fast pyrolysis of freshwater algae ...
Feb 9, 2021 · The measured higher heating value (HHV) of. Botryococcus braunii-derived oil produced at 500 ◦C is 45 MJ/kg and this bio-oil could be used as a ...<|control11|><|separator|>
[49]
[PDF] Direct Transesterification of Microalga Botryococcus braunii ...
Jul 6, 2016 · Effect of media and culture conditions on growth and hydrocarbon production by Botryococcus braunii. Process. Biochem., 40: 3125-3131. [27] Z ...
[50]
Hydrocracking of algae oil to aviation fuel-ranged hydrocarbons ...
Jul 15, 2019 · The NiMo/Al 13 -Mont catalyst achieved a C 10 −C 15 aviation fuel-ranged hydrocarbons yield of 52% for the hydrocracking of Botryococcus braunii oil at 300 °C ...
[51]
Enhanced microalgal lipid production for biofuel using different ...
The lipid yields were obtained as 56.42% and 41.31% for Botryococcus braunii and Chorella vulgaris, respectively. ... Photosynthetic efficiency. Light is ...
[52]
(PDF) Botryococcus braunii : A Renewable Source of Hydrocarbons ...
Aug 4, 2025 · Botryococcus braunii, a green colonial microalga, is an unusually rich renewable source of hydrocarbons and other chemicals.
[53]
A Holistic Approach to Managing Microalgae for Biofuel Applications
Using treated wastewater in raceway ponds, a biomass production potential of 9.2–17.8 tons·ha−1 per year could be achieved. The lipids extracted from the ...
[54]
Techno-economic analysis of milking of Botryococcus braunii for ...
Aug 10, 2025 · The commercialization of algal biofuel production faces challenges, such as high production costs and difficulties in scaling up the process.
[55]
The potential of coupling wastewater treatment with hydrocarbon ...
Different races (A, B, S, and L) of B. braunii have been identified based on the nature and chemical structure of the hydrocarbon they produce. The hydrocarbons ...
[56]
Growth characteristics of Botryococcus braunii 765 under high CO2 ...
The results showed that the strain could grow well without any obvious inhibition under all tested CO(2) concentrations with an aeration rate of 0.2 vvm, even ...Missing: wastewater treatment pilot Australia 2023
[57]
Non-destructive hydrocarbon extraction from Botryococcus braunii ...
Aug 9, 2025 · braunii CCALA-778 (race A) and B. braunii AC761 (race B), which ... Prediction of hydrocarbon yield from wet Botryococcus braunii: The ...
[58]
https://doi.org/10.1016/j.algal.2023.103156
[59]
https://link.springer.com/article/10.1007/s10811-025-03693-9
[60]
https://doi.org/10.1016/j.ultsonch.2018.05.002
[61]
https://doi.org/10.3390/proceedings2201289
[62]
https://doi.org/10.1016/j.jbiosc.2013.06.012
[63]
https://doi.org/10.1007/BF02183077
[64]
The Botryococcenes—hydrocarbons of novel structure from the alga ...
The hydrocarbon fraction of Botryococcus braunii, growing in its natural environment, has been isolated and examined. Surprisingly this fraction was found ...
[65]
Hydrocarbon composition of newly isolated strains of the green ...
Four new strains of Botryococcus braunii were isolated from Japanese waters and cultured under defined conditions. Their hydrocarbon content and composition ...
[66]
Draft Nuclear Genome Sequence of the Liquid Hydrocarbon ...
Botryococcus braunii has long been known as a prodigious producer of liquid hydrocarbon oils that can be converted into combustion engine fuels.Missing: Australia billabongs
[67]
Integrated biorefinery approach for sustainable production of ...
Feb 10, 2025 · Botryococcus braunii, a bloom forming green microalga, known for its high lipid content and potential for biofuel production has been explored ...Missing: sequestration | Show results with:sequestration
[68]
Identification of suitable Botryococcus braunii strains for non ...
Dec 7, 2020 · The strain Bot22 (64 out of 75 ranking points) seem to be the most suitable strains for the milking process. They both possess good extractant compatibility.
[69]
Botryococcus braunii strains compared for biomass productivity ...
Apr 20, 2017 · Depending on what type of hydrocarbons are produced, B. braunii is subclassified into four chemical races, designated A, B and L (Metzger and ...
[70]
Botryococcus braunii for the production of hydrocarbons and ...
Dec 19, 2017 · Two strains, AC761 which produces botryococcenes and CCALA778 which produces EPS, were selected as the most promising B. braunii strains for ...
[71]
Liquid Hydrocarbon Production Potential of a Novel Strain of the ...
Apr 24, 2014 · Botryococcus braunii is considered a promising source of non-oxygenated liquid biofuels. Harvesting and pre-extraction processing of the algal ...