石油的大量使用会导致能源枯竭和温室气体（CO2）排放的增加。为了实现经济和环境的和谐发展，必须使用可再生能源代替石油。可再生能源使用后不会造成温室气体排放的增加。生物柴油是一种理想的可再生能源, 能满足以上要求，所以近年来得到迅速发展。微藻是一种主要利用太阳能固定 CO2，生成制备生物柴油所需油脂的藻类。因此以微藻油脂为原料转化成的生物柴油是石油理想的替代品。简要介绍了产油微藻的种类和微藻油脂的合成，较详细地阐述了微藻自养培养、异养培养、生物反应器、工程微藻的最新研究进展，并初步展望了微藻产油研究的未来发展方向。

This review describes compounds produced microalgae, such as biodiesel, lipids, fatty acids (FA), triacylglycerides (TAG), and pigments (phycobilins, chlorophylls, and carotenoids). We discuss the factors inducing the accumulation of these metabolites and their economic importance. We focused on cell wall breaking methods of microalgae used to produce biodiesel. A special approach was made to extremophile microalgae used in biodiesel production. The type of methodology used in the cultivation and the use of extremophiles microalgae can permit feasible biodiesel production.

Summary Top of page Summary Introduction Content and fatty acid composition of algae Biosynthesis of fatty acids and triacylglycerols Factors affecting triacylglycerol accumulation and fatty acid composition Role of algal genomics and model systems in biofuel production Historical perspective and recent advances Path forward for algal feedstock-based biofuels Acknowledgements References Microalgae represent an exceptionally diverse but highly specialized group of micro-organisms adapted to various ecological habitats. Many microalgae have the ability to produce substantial amounts (e.g. 20 50% dry cell weight) of triacylglycerols (TAG) as a storage lipid under photo-oxidative stress or other adverse environmental conditions. Fatty acids, the building blocks for TAGs and all other cellular lipids, are synthesized in the chloroplast using a single set of enzymes, of which acetylCoA carboxylase (ACCase) is key in regulating fatty acid synthesis rates. However, the expression of genes involved in fatty acid synthesis is poorly understood in microalgae. Synthesis and sequestration of TAG into cytosolic lipid bodies appear to be a protective mechanism by which algal cells cope with stress conditions, but little is known about regulation of TAG formation at the molecular and cellular level. While the concept of using microalgae as an alternative and renewable source of lipid-rich biomass feedstock for biofuels has been explored over the past few decades, a scalable, commercially viable system has yet to emerge. Today, the production of algal oil is primarily confined to high-value specialty oils with nutritional value, rather than commodity oils for biofuel. This review provides a brief summary of the current knowledge on oleaginous algae and their fatty acid and TAG biosynthesis, algal model systems and genomic approaches to a better understanding of TAG production, and a historical perspective and path forward for microalgae-based biofuel research and commercialization.

在&quot;异养-胁迫&quot;分段培养模式下分析原始小球藻(<em>Chlorella protothecoides</em>)的生物量及油脂含量。结果表明,在500ml摇瓶中,分段培养生物量达5.32g/L,略低于一步异养培养5.45 g/L,油脂含量达34.81%,是一步异养培养的2.26倍,藻渣中微藻多糖含量由 9.57%提高到18.06%。在3L发酵罐中,一步异养培养模式下生物量为14.1 g/L,油脂含量为17.16%,微藻多糖含量为10.16%;而&quot;异养-胁迫&quot;分段培养模式下生物量13.20g/L,油脂含量40.15%,微藻多糖含量24.74%。本研究显示&quot;异养-胁迫&quot;分段培养模式是一种快速获得大量高油脂含量藻细胞的有效方法,可为规模化生产微藻生物柴油和进一步利用微藻奠定了技术基础。

Microalgae have great potential as alternative productive platforms for sustainable production of bioenergy, food, feed and other commodities. Process optimization to realize the claimed potential often comprises strains selection and improvement and also developing of more efficient cultivation, harvesting and downstream processing technology. In this work we show that inoculation with the bacterium Rhizobium strain 10II resulted in increments of up to 30% in chlorophyll, biomass and lipids accumulation of the oleaginous microalgae Ankistrodesmus sp. strain SP2-15. Inoculated cultures have reached a high lipid productivity of up to 11202mg02L 611 02d 611 after optimization. The resulting biomass presented significant levels of Ω3 fatty acids including stearidonic acid, suggesting potential as an alternative land-based source of essential fatty acids.

研究了在BG11液体培养基中添加0.1～1.5 mg·L-1 IAA对微藻TH6(Oedocladium sp. )生长和脂肪酸含量的影响.结果表明,随培养时间的延长,微藻TH6的生长量逐渐增加;与对照相比,添加不同浓度IAA对微藻TH6的生长均有不同程度的 促进作用,其中添加1.0 mg·L-1 IAA对微藻TH6生长的促进效果最佳,至培养第33天,微藻TH6的生长量比对照提高了44.34%.在培养基中添加IAA均能不同程度提高微藻TH6 的总脂肪酸含量,当IAA 浓度为0.1、0.5、1.0和1.5 mg·L-1时,总脂肪酸含量分别是对照的2.09、2.13、2.41和1.73倍.IAA对微藻TH6中软脂酸、硬脂酸、亚油酸和油酸含量的影响作用 不同.添加不同浓度IAA均能不同程度提高软脂酸的含量,当IAA浓度为1.0 mg·L-1时,软脂酸的相对含量最高,达到了28.62%;较高浓度的IAA(1.0和1.5 mg·L-1)能促进硬脂酸含量的提高, 低浓度IAA(0.1和0.5 mg·L-1)使硬脂酸含量降低;当IAA浓度为0.1～1.0 mg·L-1时,亚油酸含量较对照有不同程度提高;IAA对油酸含量的影响作用不明显.研究结果显示,含有1.0 mg·L-1 IAA的BG11液体培养基为微藻TH6的最佳液体培养基.在这一培养基中,微藻TH6的总脂肪酸含量最高,饱和及不饱和脂肪酸含量也较高,且微藻TH6 生长量最大,可作为生物柴油资源进一步研究和开发.

研究了不同植物激素（IBA、NAA、6-BA、2,4-D、TDA）对原始小球藻（Chlorella protothecoides）的生长及脂肪酸组成的影响。使用三角瓶进行静置培养,在培养基中添加0.5 mg/L的不同植物激素,结果表明：培养基中添加不同的植物激素对原始小球藻的生长有不同的影响,以2,4-D的促进效应最为明显,最终干重为1.18 g/L,是空白对照的1.2倍;不同植物激素对粗油脂含量的影响不同,其中添加2,4-D的培养液中所收获的藻粉油脂含量最高,为藻粉干重的19.74%,比空白对照高26.21%;对粗油脂进行GC-MS分析,结果显示不同植物激素的添加对于小球藻脂肪酸成分的影响不大,但略微提升了C16和C18脂肪酸的相对含量,使之更加适合作为生物柴油的来源。结合总脂收获量的高低及脂肪酸成分的不同,本试验最终确定2,4-D为小球藻培养基最理想的植物激素类添加物。

目的探讨植物激素诱导对小球藻Chlorella vulgaris细胞生物量、油脂含量及内生激素浓度的影响规律。方法分别以天然植物源脱落酸(abscisic acid,ABA)、工业合成萘乙酸(1-naphthylacetic acid,NAA)和二氯苯氧基乙酸(2,4-dichlorophenoxyacetic acid,2,4-D)诱导培养小球藻Chlorella vulgaris细胞,细胞干重法检测藻细胞生物量及油脂含量,气相色谱-质谱(GC-MS)分析脂肪酸组成,高效液相色谱-质谱(HPLC-MS)测定内生激素浓度。结果 NAA诱导对藻细胞生长和脂质合成积累表现出显著的促进效应,其最大油脂产率为418.6 mg/(L·d),分别为2,4-D和ABA诱导藻细胞的1.48和1.83倍;NAA诱导有效调整了小球藻胞内饱和脂肪酸和单不饱和脂肪酸比例,使其组成和含量更易于制备高质量生物柴油;NAA作为激素合成前体参与内生激素(吲哚乙酸、茉莉酸和水杨酸)生物合成,促进内生激素水平升高,而提高浓度的内生激素可能通过一定的信号途径刺激藻细胞生长和合成脂质。结论植物类激素NAA可作为植物源激素替代物用于低成本微藻油脂生产,为制备经济可行的、高质量生物柴油提供了新的途径。

The growth of Scenedesmus obliquus improved with increase in phytohormones concentrations (10618–10615M). Indole-3-acetic acid (IAA) supported the maximum growth at 10615M with 17.7×106cells/mL and total fatty acid of 97.9mg/g-DCW, enhancing the growth by 1.9-fold compared to control (9.5×106cells/mL). While 10615M of a newly discovered phytohormone Diethyl aminoethyl hexanoate (DAH) demonstrated a 2.5-fold higher growth with 23.5×106cells/mL and a total fatty acid content of 100mg/g-DCW. Poly-unsaturated fatty acid content increased up to 56% and 59% at 10615M of IAA and DAH, respectively. The highest carbohydrate content (33% and 34%) achieved at 10618M and 10615M of IAA and DAH, respectively. While, the highest protein content (34% and 35%) obtained at 10618M of IAA and DAH, respectively. The current investigation demonstrates that phytohormones accelerate microalgal growth and induce the quality and quantity of fatty acid content for biodiesel production.

Effects of Fe 3+ (0–0.1202g/L), Mg 2+ (0–0.7302g/L) and Ca 2+ (0–0.9802g/L) on the biomass and lipid accumulation of heterotrophic microalgae were investigated in dark environment. The biomass and lipid production exhibited an increasing trend with increasing the concentrations of metal ions. In cultures with 1.202×0210 613 02g/L Fe 3+ , 7.302×0210 613 02g/L Mg 2+ and 9.802×0210 614 02g/L Ca 2+ , the maximum biomass, total lipid content and lipid productivity reached 3.4902g/L, 47.4% and 275.702mg/L/d, respectively. More importantly, EDTA addition (1.002×0210 613 02g/L) could enhance the solubility of metal ions (iron and calcium) and increase their availability by microalgae, which evidently promote the lipid accumulation. Compared with the control, the total lipid content and lipid productivity increased 28.2% and 29.7%, respectively. These show that appropriate concentrations of metal ions and EDTA in the culture medium were beneficial to lipid accumulation of heterotrophic Scenedesmus sp. cells.

Many species of microalgae accumulate under growth-limiting conditions, such as nitrogen deprivation, large amounts of triglycerides (TAG). The regulation of this process is not clear. Here we demonstrate that sodium azide (Az) induces synthesis of high levels of TAG in the lipid-accumulating marine species Chlorella desiccata . In comparison to N deprivation, Az leads to only minor growth retardation and to smaller inhibition of photosynthesis and respiration, resulting in a 60 80% increase in TAG yield. Maximal TAG induction level by Az is strictly dependent on light intensity and requires high CO 2 . The cell morphology, TAG level and composition are similar in both treatments. From 17 tested microalgae species, 15 were responsive to Az under different culturing conditions. The results suggest that the higher TAG yield in Az-treated compared to N-deprived cultures, results from the better metabolic state and higher photosynthetic activity of the culture. The potential of Az to improve TAG yield production from microalgae is discussed.

ABSTRACT Sodium azide (Az) induces accumulation of triglycerides (TAG) in the green alga Chlorella desiccata with minimal growth retardation (Rachutin-Zalogin & Pick, joint manuscript). To clarify the mechanism of this effect, the involvement of respiration, production of reactive oxygen species (ROS) and suppression of nitrate reductase (NR) was investigated. Different respiratory inhibitors induced minor or no TAG accumulation, ruling out respiration as the primary Az target. ROS generators failed to induce massive TAG accumulation, but the singlet oxygen quencher DABCO inhibited Az-induced TAG biosynthesis and this inhibition was suppressed in 30% D2O. Az-induced TAG accumulation was observed in nitrate, but not in ammonium medium, in which growth is not dependent on NR. Effects of cyanide, cyanate, a singlet oxygen quencher, D2O and of CO2 limitation on TAG accumulation are consistent with inhibition of NR. C. desiccata NR activity is Az-sensitive. The results suggest that Az-induced TAG accumulation results primarily from photoinactivation of NR.