Formation of farnesal and 3-hydroxy-2,3-dihydrofarnesal from farnesol by protoplasts of Botryococcus braunii

Microalgae protoplasts isolation and fusion for biotechnology research

Protoplasts are microbial or vegetable cells lacking a cell wall. These can be obtained from microalgae by an enzymatic hydrolysis process in the presence of an osmotic stabilizer. In general, protoplasts are experimentally useful in physiological, geneticand bio-chemical studies, so their acquisition and fusion will continue to be an active research area in modern biotechnology. The fusion of protoplasts in microalgae constitutes a tool for strain improvement because it allows both intra and interspecific genetic recombina-tion, resulting in organisms with new or improved characteristics of industrial interest. In this review we briefly describe themethod-ology for obtaining protoplasts, as well as fusion methods and the main applications of microalgal platforms.

The history and recent advances in research of polyprenol and its derivatives

The reduction pathway leading to the formation of dolichol was clarified in 2010 with the identification of SRD5A3, which is the polyprenol reductase. The finding inspired us to reanalyze the length of the major chain of polyprenol and dolichol from several plant leaves, including mangrove plants, as well as from animal and fish livers by 2D-TLC. Polyprenol- and dolichol-derived metabolites such as polyprenylacetone and epoxydolichol were found together with rubber-like prenol. This review focuses on analyses of polyprenol and its derivatives, including recently found epoxypolyprenol and polyprenylacetone. Attention has also been paid to the chromatographic behavior of rubber-like prenol on TLC.

Sugar availability modulates polyisoprenoid and phytosterol profiles in Arabidopsis thaliana hairy root culture

Sugars are recognized as signaling molecules regulating the biosynthesis of secondary metabolites in plants. Here, a modulatory effect of sugars on dolichol and phytosterol profiles was noted in the hairy roots of Arabidopsis thaliana. Arabidopsis roots contain a complex dolichol mixture comprising three groups ('families') of dolichols differing in the chain-length. These dolichols, especially the longest ones are accompanied by considerable amounts of polyprenols of the same length. The spectrum of polyisoprenoid alcohols, i.e. dolichols and polyprenols, was dependent on sugar type (glucose or sucrose) and its concentration in the medium. Among the long-chain dolichols Dol/Pren-20 (dolichol or prenol molecule composed of 20 isoprene residues) and Dol/Pren-23 were the main components at 0.5% and 2% glucose, respectively. Moreover, the ratio of polyprenols versus respective dolichols was also modulated by sugar in this group of polyisoprenoids, with polyprenols dominating at 3% sucrose and dolichols at 2% glucose. Glucose concentration affected the expression level of genes encoding cis-prenyltransferases, enzymes responsible for elongation of the polyisoprenoid chain. The most abundant phytosterols of the A. thaliana roots, β-sitosterol, stigmasterol and campesterol, were accompanied by corresponding stanols and traces of brassicasterol, stigmast-4,22-dien-3-one and stigmast-4-en-3-one. Similar to the polyisoprenoids, sterol profile responded to the sugar present in the medium, β-sitosterol dominating in roots grown on 3% or lower glucose concentrations and stigmasterol in 3% sucrose. These results indicate an involvement of sugar signaling in the regulation of cis-prenyltransferases and phytosterol pathway enzymes.

Botryococcus braunii: a rich source for hydrocarbons and related ether lipids

This paper presents a review on Botryococcus braunii, a cosmopolitan green colonial microalga characterised by a considerable production of lipids, notably hydrocarbons. Strains like wild populations of this alga differ in the type of hydrocarbons they synthesise and accumulate: (1) n-alkadienes and trienes, (2) triterpenoid botryococcenes and methylated squalenes, or (3) a tetraterpenoid, lycopadiene. In addition to hydrocarbons and some classic lipids, these algae produce numerous series of characteristic ether lipids closely related to hydrocarbons. This review covers the algal biodiversity, the chemical structures and biosynthesis of hydrocarbons and ether lipids and the biotechnological studies related to hydrocarbon production.

Characterization of botryococcene synthase enzyme activity, a squalene synthase-like activity from the green microalga Botryococcus braunii, Race B

The extracellular matrix of the alga Botryococcus braunii, Race B, consists mainly of botryococcenes, which have potential as a hydrocarbon fuel. Botryococcenes are structurally similar to squalene raising the possibility of a common enzyme for the biosynthesis of both. While B. braunii squalene synthase (SS) enzyme activity has been documented, botryococcene synthase (BS) enzyme activity has not been. In the current study, an assay for BS activity has been developed and used to show that many of the assay conditions for BS enzyme activity are similar to those of SS. However, SS enzyme activity is stimulated by Tween 80 while BS enzyme activity is inhibited. Moreover, BS enzyme activity was correlated with the accumulation of botryococcenes during a B. braunii culture growth cycle, which was distinctly different from the profile of SS enzyme activity. While the current results indicate a conservation of enzymological features amongst the BS and SS enzymes, raising the possibility of one enzyme capable of catalyzing both activities, they are also consistent with these two activities arising from separate and distinct enzymes.

Botryococcus braunii: a renewable source of hydrocarbons and other chemicals

Botryococcus braunii, a green colonial microalga, is an unusually rich renewable source of hydrocarbons and other chemicals. Hydrocarbons can constitute up to 75% of the dry mass of B. braunii. This review details the various facets of biotechnology of B. braunii, including its microbiology and physiology; production of hydrocarbons and other compounds by the alga; methods of culture; downstream recovery and processing of algal hydrocarbons; and cloning of the algal genes into other microorganisms. B. braunii converts simple inorganic compounds and sunlight to potential hydrocarbon fuels and feedstocks for the chemical industry. Microorganisms such as B. braunii can, in the long run, reduce our dependence on fossil fuels and because of this B. braunii continues to attract much attention.

Molecular characterization of squalene synthase from the green microalga Botryococcus braunii, race B

The green microalga Botryococcus braunii produces large amounts of liquid hydrocarbons and is classified into three races, depending on the type of the hydrocarbon produced. The B race produces two types of triterpenoid hydrocarbons, squalene and botryococcene, both of which are putative condensation products of farnesyl diphosphate. In an attempt to better understand the regulation involved in the production of squalene and botryococcene, we have isolated and characterized a squalene synthase (SS) gene from the B race of B. braunii. A 366-bp cDNA fragment was initially obtained from the B race utilizing a reverse transcription/polymerase chain reaction and degenerate primers based on conserved amino acid sequences found in all SS enzymes. Using this putative SS fragment as a probe, a 2632-bp cDNA clone was isolated from a cDNA library. This cDNA contained an open reading frame coding for a protein with 461 amino acids and a predicted molecular mass of 52.5 kDa. Comparison of the Botryococcus SS (BSS) with SS from different organisms showed 52% identity with Nicotiana tabacum, 51% with Arabidopsis thaliana, 48% with Zea mays, 40% with rat, 39% with yeast, and 26% with Zymomonas mobilis. Expression of full-length and carboxy-terminus truncated BSS cDNA in Escherichia coli resulted in significant levels of bacterial SS enzyme activity but no botryococcene synthase activity. RNA blot hybridization analysis of algal cultures during a culture cycle indicated that BSS gene expression is preferential during rapid growth. Given that the DNA blot analysis indicated only a single copy of the SS gene in the algal genome, these results suggest either that there exists coordinate expression of separate synthase genes for squalene and botryococcene biosynthesis or that there might be unique physiological conditions controlling the SS vs botryococcene synthase activity of a single peptide species.