不同饵料对卤虫生长、总脂含量及脂肪酸组成的影响

为了提高养殖卤虫的饵料营养价值,了解其不同生长阶段营养成分变化情况,采用单因子试验研究了8种饵料（三角褐指藻、小球藻、微绿球藻、酵母液、三角褐指藻＋小球藻＋微绿球藻、三角褐指藻＋酵母液、小球藻＋酵母液和微绿球藻＋酵母液）对卤虫生长、总脂含量及脂肪酸组成的影响,结果表明：不同饵料种类对卤虫生长、总脂含量及脂肪酸组成的影响显著（P＜0.05）,增长率,以三角褐指藻＋酵母液最优;总脂含量、以三角褐指藻最优（19.67%）,除酵母液外,与其它饵料相差不显著（P＞0.05）;脂肪酸组成效果,以微绿球藻组最优（EPA：18.01%,DNA：0.55%,（n-3）HUFA：19.08%）,与三角褐指藻组相差不大（P＞0.05）,显著高于其它各组（P＞0.05）.同时以三角褐指藻为饵料,研究了卤虫不同生长阶段（体长2、4、6、8、10 mm）总脂含量、脂肪酸组成变化,结果表明：卤虫体长2～10 mm总脂含量为14.27%～20.93%,随体长的增长降低;EPA、DHA及（n-3）HUFA的含量,均随体长的增长降低,EPA含量为：10.47%～20.77%,DNA含量为：0～0.70%,（n-3）HUFA含量为：10.85%～22.01%.结论认为,卤虫以三角褐指藻或三角褐指藻＋酵母液为饵料培养营养价值最佳,其体长小于6 mm营养价值较佳.     

三种海洋微藻和三种淡水微藻脂肪酸组成特征的比较分析

比较了3种海洋微藻：简单角刺藻(Chaetoceros simplex)、绿色巴夫藻(Pavlova viridis)、扁藻(Platymonas sp.)和3种淡水微藻：蛋白核小球藻(Chlorella pyrenoidosa)、斜生栅藻(Scenedesmus obliquua)、极大螺旋藻(Spirulina maxima)的脂肪酸组成。结果表明：海洋微藻的饱和脂肪酸种类相对比淡水微藻多,前者的碳链长度在14碳到20碳之间,后者主要有C16：0和C18：0。二者单不饱和脂肪酸均是以C16：1ω7和C18：1ω9为主。多不饱和脂肪酸中,海洋微藻以二十碳五稀酸(EPA)和二十二碳六稀酸(DHA)为主,其中,绿色巴夫藻含有24．34％的EPA和11．48％的DHA,简单角刺藻含有13．24％的EPA;淡水微藻以18碳为主,其中,极大螺旋藻含有24．02％的γ-亚麻酸(GLA)。     

藻类的养殖和利用

藻的种类多,分布广,但从分布的水体性质来分只有两大类,即海水藻和淡水藻。藻类养殖相应的也只有两种类型,一种为海水养殖,另一种为淡水养殖。我国海水养殖的藻类有海带、紫菜、江篱、石花菜、激激菜和杜氏菜,前5种为大型海藻,后1种为单细胞鞭毛类。海水养殖的优点：（）我国海域辽阔,海岸线长,可供氧养殖的水面大;（2）海水是宝贵的自然资源,海水中含有许多藻类生长繁殖所必需的营养元素;（3）有些特殊的水体如废盐田,只要气候适宜可以用来培养某些海藻。目前我国养殖淡水藻种类不多,主要有螺旋藻、小球藻和鱼腥藻（即固氮蓝…     

13种微藻的脂肪酸组成分析

分析了13种微藻(包括7种绿藻,5种杂色藻和1种红藻)的总脂含量和脂肪酸组成,结果表明,不同门类微藻的脂肪酸组成差异较大:绿藻的脂肪酸组成以C16和C18为主;杂色藻类的脂肪酸组成相近,金藻门含有14:0、16:0、18:1、18:4等特征脂肪酸,三角褐指藻主要的脂肪酸为14:0、16:0、16:1、16:3和20:5,而粉核油球藻的脂肪酸以14:0、16:0、20:5为主;紫球藻的脂肪酸组成以16:0、20:4和20:5为主。在测试的13种微藻中,杜氏盐藻的亚麻酸含量最高,占总脂肪酸的60.9%;等鞭金藻的十八碳四烯酸含量最高,占总脂肪酸的19.6%;紫球藻和粉核油球藻中花生四烯酸与二十碳五烯酸(EPA)含量分别占总脂肪酸的17.1%和20.9%。     

5种藻和2种酵母对萼花臂尾轮虫饵料效果的比较研究

采用蛋白质和脂肪酸两项指标评价了7种饵料,包括5种藻(蛋白核小球藻、斜生栅藻、小球衣藻、卵形隐藻、中型裸藻)和2种酵母(面包酵母和啤酒酵母)对萼花臂尾轮虫的营养价值。蛋白质的评价结果显示,轮虫体总氮(TN)的含量为10．08％;粗蛋白(CP)的含量为63．0％;总氨基酸(TAA)占粗蛋白的48．10％;总必需氨基酸(TEAA)占粗蛋白的22．02％;TEAA与TAA的比值(TEAA／TAA)为45．8。在7种饵料中TN的含量在6．57％—10．96％之间,其中在卵形隐藻中的含量最高,在面包酵母中的含量最低;粗蛋白的含量介于41．06％—68．54％之间,在各饵料中含量由高到低的排列顺序与TN一致;TAA的含量在54．694—73．235之间,其中在斜生栅藻中的含量最高,在卵形隐藻中含量最低;TEAA的含量在23．836—34．136之间,其中在面包酵母中含量最高,在卵形隐藻中含量最低：TEAA／TAA比值在43．3—49．1之间,其中两种酵母的该比值最大。实验共测出17种氨基酸。轮虫蛋白质中以组氨酸含量最低(0．540％),其次为蛋氨酸(0．556％)和胱氨酸(0．762％);含量最高的是天门冬氨酸(5．206％)和甘氨酸(4．571％)。其饵料蛋白质中含量较低的是蛋氨酸(0．421％—1．495％)、组氨酸(0．675％—1．967％)和胱氨酸(0．439％—3．332％);含量较高的是谷氨酸(6．073％—11．447％)、天门冬氨酸(5．519％—8．281％)和亮氨酸(4．143％—7．473％)。分别用全卵蛋白和轮虫蛋白作为标准测得各种饵料的第一限制氨基酸有所不同,前有6种是蛋氨酸,1种为组氨酸(蛋白核小球藻);后有5种为异亮氨酸,另2种分别为蛋氨酸(蛋白核小球藻)和赖氨酸(啤酒酵母)。本项综合结果显示,蛋白核小球藻、斜生栅藻和两种酵母的蛋白质营养价值较高。脂肪酸的评价结果显示,饵料中粗脂肪的含量在1．64％—15．41％之间,其中中型裸藻中含量最高,啤酒酵母中含量最低。在7种饵料中共测出29种脂肪酸,其中中型裸藻和卵形隐藻中含量最为丰富,分别检出24种和22种;而在面包酵母和啤酒酵母中较缺乏,只检出9种和13种。5种饵料中不饱和脂肪酸的含量高于饱和脂肪酸的含量,其余2种饵料(斜生栅藻和啤酒酵母)则相反;5种藻中不饱和脂肪酸含量最高的是18：3ω3,其值在11．76％—26．58％;卵形隐藻的18：4ω3和小球衣藻的16：4ω3的含量亦较高,分别为22．59％和15．48％;在卵形隐藻和中型裸藻中,长碳链(二十碳以上的)不饱和脂肪酸的含量丰富,其含量为：中型裸藻16．2％,卵形隐藻18．7％,而在其他饵料中则较缺乏。除啤酒酵母外,饵料中缺乏的高度不饱和脂肪酸,均可在其培养的轮虫中检出,说明该轮虫可能具有将18：4ω3和18：3ω3转化为20：5ω3和22：6ω3等ω3系列高度不饱和脂肪酸(ω3HUFA)的代谢机制。用藻培养的轮虫,富含鲤科鱼类所必需的脂肪酸(18：2ω6和18：3ω3),其中蛋白核小球藻轮虫的含量最高(17．36％和24．64％),其次为斜生栅藻轮虫(12．23％和21．66％);面包酵母轮虫的ω3HUFA的含量占第四位,即脂肪酸营养价值较高。由此项指标得出结论,蛋白核小球藻和斜生栅藻是该轮虫工厂化培养的首选饵料,面包酵母是很有前途的饵料。这与7种饵料的投喂效果实验和蛋白质营养价值的评价结果基本一致。     

三角褐指藻丙二酰单酰辅酶 A:酰基载体蛋白转酰基酶的功能分析

【背景】丙二酰单酰辅酶A:酰基载体蛋白转酰基酶(malonyl coenzyme A:acyl carrier protein transacylase, MCAT)是Ⅱ型脂肪酸合酶(fatty acid synthase Ⅱ, FASⅡ)的重要亚基,与脂肪酸合成直接相关,然而关于微藻MCAT的信息却很少。【目的】验证三角褐指藻MCAT的功能。【方法】在模式硅藻三角褐指藻的全基因组序列中发现了一个可能的mcat基因序列,对其进行生物信息学分析,构建原核表达载体,并转入MCAT缺陷型大肠杆菌L48菌株中,最后利用GC-MS分析突变株脂肪酸的成分和含量。【结果】三角褐指藻MCAT主要结构为α-螺旋和无规则卷曲,与圆柱脆杆藻的亲缘关系最为接近,为protits型MCAT;三角褐指藻MCAT的表达使MCAT缺陷型大肠杆菌L48菌株恢复了合成脂肪酸的功能;对L48回复突变株的脂肪酸组成进行分析,发现该酶对C14:0具有底物偏好性,从而促进中长链脂肪酸如C16:0和C17:1的合成,这一特点与protits型MCAT的特性基本相符。【结论】三角褐指藻MCAT能促进脂肪酸的合成,这为微藻脂肪酸合成及...     

三角褐指藻甘油酯对氮胁迫的响应

【背景】三角褐指藻作为生物燃料潜在的生产者,在胁迫条件下能通过改变其甘油酯组成来适应外部环境的变化,同时伴随着生物燃料原料甘油三酯(TAG)的积累,研究三角褐指藻甘油酯对氮胁迫的响应机制有利于深入认识TAG的积累过程。【目的】通过分析三角褐指藻在正常和氮胁迫条件下各类脂质含量及其脂肪酸成分的变化,揭示氮胁迫诱导积累的TAG酰基主要来源,以及在胁迫前生成的各极性甘油酯脂肪酸的去向,从而为进一步认识三角褐指藻对氮胁迫的响应机制提供新信息。【方法】利用高效薄层色谱结合气相色谱法分析三角褐指藻在正常和氮胁迫条件下的脂肪酸及甘油酯组分的变化。【结果】三角褐指藻在氮胁迫条件下TAG含量增加至57.8 mg/g时,总甘油酯含量几乎不变,但各甘油酯含量变化差异很大,表现为各极性脂含量显著降低。在此期间,各类甘油酯脂肪酸组成含量的变化表明,三角褐指藻TAG主要积累饱和及单不饱和脂肪酸,即16:0和16:1n7,分别以从头合成及原有极性脂转化为主,极性脂的部分二十碳五烯酸(EPA)作为酰基供体也向TAG发生了转化;此外组成极性脂的多不饱和脂肪酸16:2n4、16:3n4及EPA分解导致其含量显著下降。【结论】当氮胁迫诱导的三角褐指藻TAG含量为57.8 mg/g时,积累的TAG酰基中有48%来自从头合成,52%来自极性脂转化;而氮胁迫诱导所减少的极性脂酰基中有54%转化成TAG,46%发生了分解。     

萼花臂尾轮虫培养滤液对铜绿微囊藻、斜生栅藻和小球藻群体形成及生长的影响

为探索浮游动物和藻类之间可能存在的信息传递,研究了萼花臂尾轮虫培养滤液对铜绿微囊藻、斜生栅藻和小球藻的生长及群体形成的影响.把萼花臂尾轮虫按1000个·L^-1的初始密度置于小球藻中培养24h后,用孔径0.15μm的微孔滤膜抽滤,得到轮虫培养滤液,此滤液中含有轮虫在生活过程中释放的一些信息化学物质.将轮虫培养滤液以20%的比例分别加入纯培养的铜绿微囊藻、斜生栅藻和小球藻中,进行为期7d的试验.结果表明,萼花臂尾轮虫培养滤液能显著地促进斜生栅藻的群体形成,而对铜绿微囊藻和小球藻在群体形成方面没有显著作用.另外,该滤液能显著提高小球藻种群的增长,对铜绿微囊藻和斜生栅藻的生长无明显影响.3种藻类对萼花臂尾轮虫的潜在牧食采取了不同的生态策略:斜生栅藻形成群体,增大摄食阻力,从而降低被摄食的风险;小球藻通过提高增长率来抵消被取食的损失;铜绿微囊藻是通过其它方式来降低被牧食(例如毒素).这些方式分别是这些藻类维持种群规模的反牧食防御策略之一.     

光强对两种硅藻光合作用、碳酸酐酶和RubisCO活性的影响

为研究海洋浮游硅藻光合固碳能力与光强的关系, 以三角褐指藻和威氏海链藻为实验材料, 测定了不同光强培养下三角褐指藻和威氏海链藻生长、光合特性、碳酸酐酶和核酮糖-1, 5-二磷酸羧化/氧化酶活性(RubisCO)的变化, 结果显示高光强促进两种硅藻的生长, 但对威氏海链藻的影响更明显。高光强导致两种硅藻叶绿素a、c含量、光系统Ⅱ的最大光化学效率和实际光化学效率明显下降, 非光化学淬灭系数明显升高, 但对光化学淬灭系数并没有明显影响。在高光下威氏海链藻和三角褐指藻胞内外碳酸酐酶活性明显升高。在高光强下培养的威氏海链藻RubisCO活性明显高于低光下培养, 但三角褐指藻正好相反, 不管高光还是低光培养威氏海链藻RubisCO活性始终高于三角褐指藻。以上结果表明不同硅藻对光强变化的响应存在差异, 它们可以通过调节光合生理特征、光合固碳关键酶和CO2供应以适应光强的变化。       

苯胺、苯酚对淡水藻类生长的影响

用生物检验法研究了苯胺、苯酚对蛋白核小球藻、斜生栅藻生长的影响,测定了两种藻类在5 d内对不同浓度苯胺、苯酚的降解或在藻细胞内的富集情况.结果表明,苯胺、苯酚对两种淡水藻类的致毒作用有所不同,对于同一种藻类,苯胺毒性大于苯酚;在同一毒物浓度下,栅藻表现更为敏感.在较低浓度下,两种淡水藻类均能降解或吸收一部分有机毒物,其中对苯酚的降解能力较强.     

Fatty acid profiling and molecular characterization of some freshwater microalgae from India with potential for biodiesel production

We determined the fatty acid compositions of six species of freshwater microalgae belonging to the Chlorophyta, which were isolated from freshwater bodies in Assam, India. All six microalgae -Desmodesmus sp. DRLMA7, Desmodesmus elegans DRLMA13, Scenedesmus sp. DRLMA5, Scenedesmus sp. DRLMA9 Chlorella sp. DRLMA3 and Chlorococcum macrostigmatum DRLMA12-showed similar fatty acid profiles 16:0, 16:4, 18:1, 18:2, and 18:3 as major components. We also compared fatty acid compositions during the late exponential and stationary growth phases of D. elegans DRLMA13 and Scenedesmus sp. DRLMA9 in BG11 medium. We observed enhanced percentages of total saturated and monounsaturated fatty acids with a concomitant decrease in polyunsaturated fatty acid content upon the prolonged cultivation of both microalgae. Distinct morphological features of microalgal isolates were determined by scanning electron microscopic (SEM) studies. An ornamented cell wall was found in D. elegans DRLMA13, which is characteristic of small spineless species of Desmodesmus. The isolated microalgae were further distinguished through analysis of internal transcribed spacer 2 (ITS2) secondary structures and compensatory base changes (CBCs). Analysis of CBCs showed the relatedness of Chlorella sp. DRLMA3 with other Chlorella-like organisms, but it does not belong to the clade comprising Chlorella sensu stricto, which includes Chlorella vulgaris. The CBC count between Scenedesmus sp. DRLMA9 and other species of Scenedesmus provides evidence that this isolate represents a new species.     

Comparison of neutral lipid profile of various trilaminar outer cell wall (TLS)-containing microalgae with emphasis on algaenan occurrence

The neutral lipid profiles of nine species of thin trilaminar outer wall (TLS)-containing freshwater and marine microalgae from the class of Chlorophyceae were studied with emphasis on the relationship between the lipid content and the occurrence of insoluble non-hydrolysable biopolymer (i.e. algaenan). All the freshwater microalgae produce a highly aliphatic algaenan. In sharp contrast, no algaenan was isolated from the two marine microalgae, Chlorella marina and Chlorella minutissima marina, supporting the absence of a close relationship between the presence of TLS and the occurrence of algaenan. High molecular weight straight-chain hydrocarbons (C23-C29) were identified in most of the algaenan-producing microalgae and in the algaenan-devoid C. minutissima marina, whereas only low molecular weight hydrocarbons were detected in algaenan-producing Scenedesmus subspicatus and in algaenan-devoid C. marina. Sterols, phytol and fatty alcohols were the major constituents of the polar fraction of the neutral lipids of all the microalgae investigated. High molecular weight saturated or mono-unsaturated alcohols were detected in C. emersonii and in all the microalgae belonging to the genus Scenedesmus. High amounts of saturated C30 and C32 alpha,omega-diols were also detected in S. subspicatus, S. armatus and S. pannonicus. Three classes of lipids were encountered in very small amounts in the medium polarity fraction of the neutral lipids of the microalgae investigated: (i) Monoesters composed predominantly of saturated C16 or C18 fatty acids and saturated C8, C16 or C18 alcohols and (ii) long-chain methyl ketones from C25 to C31 were detected in several species and (iii) methyl esters of fatty acids ranging from C16 to C28 were identified in all the microalgae. Attempts to use the neutral lipid composition and particularly the unusual long-chain lipids, as specific indicators of the occurrence of algaenan in TLS-containing microalgae were unsuccessful.     

Differential regulation of fatty acid biosynthesis in two Chlorella species in response to nitrate treatments and the potential of binary blending microalgae oils for biodiesel application

This study was undertaken to investigate the effects of different nitrate concentrations in culture medium on oil content and fatty acid composition of Chlorella vulgaris (UMT-M1) and Chlorella sorokiniana (KS-MB2). Results showed that both species produced significant higher (p<0.05) oil content at nitrate ranging from 0.18 to 0.66 mM with C. vulgaris produced 10.20-11.34% dw, while C. sorokiniana produced 15.44-17.32% dw. The major fatty acids detected include C16:0, C18:0, C18:1, C18:2 and C18:3. It is interesting to note that both species displayed differentially regulated fatty acid accumulation patterns in response to nitrate treatments at early stationary growth phase. Their potential use for biodiesel application could be enhanced by exploring the concept of binary blending of the two microalgae oils using developed mathematical equations to calculate the oil mass blending ratio and simultaneously estimated the weight percentage (wt.%) of desirable fatty acid compositions.     

高产油小球藻的筛选及其油脂分析

小球藻广泛分布于各种生境,特别是淡水环境中,适应性强。其同化产物主要是淀粉,但在环境胁迫条件下可显著积累中性脂,其脂肪酸类型主要为C16和C18,适合作为生物柴油的原料。我们从中国部分地区水体中分离纯化到若干株小球藻,通过薄层层析比较分析了21株产油小球藻的油脂含量,筛选到一株三酰基甘油含量较高的藻株Chlorella sp.NMX37N。其适宜生长温区为15—35℃,在25℃时生长速率最快,比生长速率为0.53/d,生长的最适光强为250μmol photons/(m2.s)。批量培养实验显示,藻细胞的三酰基甘油含量随培养时间延长而增加,并在培养的稳定期达到最大值,此时培养液中氮基本被耗尽。在批量培养条件下培养Chlorella sp.NMX37N约40d,藻细胞中总脂含量可达到33%左右,与此相比通过两步培养方式,将培养至对数后期(约20d)的藻细胞缺氮处理48h后,得到的总脂产率相当。通过两步培养方式可以大大缩短培养时间,使得该藻细胞快速有效积累油脂。另外,气相色谱分析显示,该藻的总脂和三酰基甘油的脂肪酸均以C16∶0和C18∶2为主,占总脂肪酸的70%以上,且不含C20以上的长链脂肪酸,可以作为优质的生物柴油原料。     

FATTY ACIDS AND HYDROXY FATTY ACIDS IN THREE SPECIES OF FRESHWATER EUSTIGMATOPHYTES

The monocarboxylic fatty acids and hydroxy fatty acids of three species of freshwater microalgae—Vischeria punctata Vischer, Vischeria helvetica (Vischer et Pascher) Taylor, and Eustigmatos vischeri (Hulbert) Taylor, all from the class Eustigmatophyceae— were examined. Each species displayed a very similar distribution of fatty acids, the most abundant of which were 20:5n-3, 16:0, and 16:1n-7; C₁₈ polyunsaturated fatty acids were minor components. These fatty acid distributions closely resemble those found in marine eustigmatophytes but are quite distinct from those found in most other algal classes. These microalgae also contain long-chain saturated and unsaturated monohydroxy fatty acids. Two distinct types of hydroxy fatty acids were found: a series of saturated α-hydroxy acids ranging from C₂₄ to C₃₀ with a shorter series of monounsaturated α-hydroxy acids ranging from C₂₆ to C₃₀ together with a series of saturated β-hydroxy acids ranging from C₂₆ to C₃₀. The latter have not previously been reported in either marine or freshwater microalgae, although C₃₀ to C₃₄ midchain (ω-18)-hydroxy fatty acids have been identified in hydrolyzed extracts from marine eustigmatophytes of the genus Nannochloropsis, and C₂₂ to C₂₆ saturated and monounsaturated α-hydroxy fatty acids have been found in three marine chlorophytes. These findings have provided a more complete picture of the lipid distributions within this little studied group of microalgae as well as a range of unusual compounds that might prove useful chemotaxonomic markers. The functions of the hydroxy fatty acids are not known, but a link to the formation of the lipid precursors of highly aliphatic biopolymers is suggested.     

CO2 biofixation and fatty acid composition of Scenedesmus obliquus and Chlorella pyrenoidosa in response to different CO2 levels

In this study, Scenedesmus obliquus SJTU-3 and Chlorella pyrenoidosa SJTU-2 were cultivated with 0.03%, 5%, 10%, 20%, 30%, 50% CO(2). The two microalgae could grow at 50% CO(2) (>0.69 g L(-1)) and grew well (>1.22 g L(-1)) under CO(2) concentrations ranging from 5% to 20%. Both of the two examined microalgae showed best growth potential at 10% CO(2). The maximum biomass concentration and CO(2) biofixation rate were 1.84 g L(-1) and 0.288 g L(-1) d(-1) for S. obliquus SJTU-3 and 1.55 g L(-1) and 0.260 g L(-1) d(-1) for C. pyrenoidosa SJTU-2, respectively. The main fatty acid compositions of the two examined microalgae were fatty acids with C(16)-C(18) (>94%) under different CO(2) levels. High CO(2) levels (30-50%) were favorable for the accumulation of total lipids and polyunsaturated fatty acids. The present results suggested that the two microalgae be appropriate for mitigating CO(2) in the flue gases and biodiesel production.     

Isolation and evaluation of oil-producing microalgae from subtropical coastal and brackish waters

Microalgae have been widely reported as a promising source of biofuels, mainly based on their high areal productivity of biomass and lipids as triacylglycerides and the possibility for cultivation on non-arable land. The isolation and selection of suitable strains that are robust and display high growth and lipid accumulation rates is an important prerequisite for their successful cultivation as a bioenergy source, a process that can be compared to the initial selection and domestication of agricultural crops. We developed standard protocols for the isolation and cultivation for a range of marine and brackish microalgae. By comparing growth rates and lipid productivity, we assessed the potential of subtropical coastal and brackish microalgae for the production of biodiesel and other oil-based bioproducts. This study identified Nannochloropsis sp., Dunaniella salina and new isolates of Chlorella sp. and Tetraselmis sp. as suitable candidates for a multiple-product algae crop. We conclude that subtropical coastal microalgae display a variety of fatty acid profiles that offer a wide scope for several oil-based bioproducts, including biodiesel and omega-3 fatty acids. A biorefinery approach for microalgae would make economical production more feasible but challenges remain for efficient harvesting and extraction processes for some species.     

Fatty acids as biomarkers of microalgae

Microalgae are primary producers of the food chain and hold prominence towards pharmaceutical and nutraceutical applications. Fatty acids (FAs) are one of the primary metabolites of microalgae, which enrich their utility both in the form of food and fuels. Additionally, the vast structural diversity coupled with taxonomic specificity makes these FAs as potential biomarkers. The determination of lipid and fatty acid profiling of 12 different strains of microalgae has been accomplished in this study and further discussed in respect to their chemotaxonomic perspective in microalgae. Palmitic acid (C16:0) and oleic acid (C18:1n9c) were found to be dominant among the members of Cyanophyceae whereas members of Chlorophyceae were rich in palmitic acid (C16:0), oleic acid (C18:1n9c) and linoleic acid (C18:2n6). The application of principal component analysis (PCA) and algorithmic hierarchical clustering (AHC) resulted in the segregation of the studied microalgal strains into 8 different orders belonging to 2 distinct phyla according to their phylogenetic classification. Nutritionally important FAs like eicosapentaenoic acid (EPA, C20:5n3) and docosahexaenoic acid (DHA, C22:6n3) were detected only in Chlorella sp. belonging to Chlorophyceaen family. Differential segregation of microalgae with respect to their fatty acid profile indicated the potential utility of FAs as biomarkers.     

Lipid Content and fatty acid composition of algal communities in sea-ice and water from the Weddell Sea (Antarctica)

The lipid and fatty acid compositions of microalgae were investigated in sea-ice and water samples from six different habitats of the Weddell Sea (Antarctica). All sea-ice samples and ice-associated water contained high algal biomass dominated by centric and pennate diatoms. Cells partially filled with oil droplets and resting spores were found. In the cells from the ice platelet layer triacylglycerols formed the largest component of the lipids. The fatty acid composition of sea-ice microalgae was dominated by the 16:1(n-7), 16:0, 18:1(n-9) and 20:5 (n-3) fatty acids. Except 18:1, they are typical for diatom fatty acids. These fatty acids were most abundant in pieces of first year ice with a brown colouration (brown-ice) and in the water column directly below sea-ice (sub-ice water). The small amounts of non-diatom acids, as 22:6 (n-3) and 18:4 (n-3), clearly showed that the sea-ice communities were not purely composed of diatoms. The most striking difference, in comparison to the general fatty acid composition of diatoms, was the high proportion of the 18:1 fatty acid in all samples, which might be caused by detrital material or lipid accumulation within cells and resting spores. In general, no clear adaptation of the fatty acid composition to the Antarctic and sea-ice environment was found. The fatty acid composition of the particulate matter from the water column was totally different from all other samples dominated by the saturated fatty acids 16:0 and 18:0.