低氮胁迫对两种魏氏藻生长和油脂积累的影响

为了评价低氮胁迫对真眼点藻纲的两株高产油微藻(斧形魏氏藻和点状魏氏藻)的生长和油脂积累的影响,实验设计中将原改良BG-11培养基中的硝酸钠浓度降低为3.6 mmol/L(0.3 g/L)。结果表明:在此浓度下斧形魏氏藻和点状魏氏藻的最高生物量分别为8.21 g/L和9.07 g/L;两者的总脂、中性脂和总脂肪酸含量(占干重)都随着培养时间的延长而不断增加,培养至第18天时分别达到56.4%,64.7%;54%,63.3%;43.5%,45.5%。这两种微藻的主要脂肪酸都含有豆蔻酸、棕榈酸、棕榈油酸、油酸、亚油酸、花生四烯酸和二十碳五烯酸,均适合于生物柴油的生产。它们的总脂、中性脂和总脂肪酸的单位体积产率分别为0.257 g/(L·d),0.326 g/(L·d);0.246 g/(L·d),0.319 g/(L·d)和0.198 g/(L·d),0.229 g/(L·d)。这说明两种微藻在低氮胁迫下都能够获得较高的油脂产率。     

富油微藻——尖状栅藻生物质生产与奶牛场废水处理相结合的效果研究

尖状栅藻(Scenedesmus acuminatus)是一株新近分离的富含油脂淡水绿藻,分别选用4种不同NaNO3初始浓度的BG-11培养基和4种不同浓度的奶牛场废水,在Φ3.0 cm柱状光生物反应器中对其进行培养。试验结果显示,在BG-11培养组中,NaNO3初始浓度为6.0mmol/L时尖状栅藻的生物量最大,达到9.5 g/L;3.6 mmol/L时总脂含量最高,为藻体干重的62.6%。在废水培养组中,100%废水培养时藻生物量最大,达到12.2 g/L;25%的废水培养时总脂含量最高,为藻体干重的62.4%;尖状栅藻的脂肪酸碳链长度为14~18 C,与石化柴油的平均碳链长度十分相近;在培养过程中该藻能有效地去除废水中的氮和磷,去除效率分别达到93.2%和99.4%。利用奶牛场废水培养富含油脂的尖状栅藻(S.acuminatus)不仅能够有效去除废水中的氮和磷等营养成分,还能为生物柴油生产提供有价格竞争优势的原料。     

一种优化Botryococcus braunii-357生物膜油脂的方法

脂肪酸的组成与结构是影响微藻生物柴油物理特性的重要因素。胞外聚合物(EPS)有助于微藻吸附生长和生物膜的形成。为了研究EPS对微藻生物膜油脂含量及脂肪酸组成的影响,对布朗葡萄藻生物膜进行EPS刺激培养,同时设计营养抑制组作为对照。结果显示:抑制组和EPS组的油脂含量分别由16.54%提高至42.2%和51.3%,油脂的中性三酰甘油酯(TAG)占比均达93%左右,饱和脂肪酸分别占55.4%,62.6%,不饱和脂肪酸分别占38.7%,31.0%。不饱和脂肪酸方面,抑制组的油酸分子均为反式结构,EPS组均为顺式结构。用EPS刺激生物膜藻体,所得微藻油的油脂含量、纯度、日产率以及TAG比例都得以提高,油脂脂肪酸组成和品质得到改善。     

斜生栅藻产微生物油脂的研究

微藻类微生物可以产生油脂,油脂可以转化为生物柴油。以废蔗渣中的含碳有机物作为原料培养斜生栅藻,通过对比实验和分析斜生栅藻的生长量、产油量、产油率,得出斜生栅藻产油率最高的水解液含量,通过正交实验,得出产油率最高的环境条件。实验结果表明,pH值对斜生栅藻产油的影响最大,当pH值为7.0、光照时长为18.0 h、氮含量100.0 mmol/L时斜生栅藻的产油脂率达到最大,为44.35%。     

硅藻生长优化富集油脂的促进机理

为了促进硅藻生长富集油脂并转化制取生物柴油的能力,以纤细角毛藻和新月菱形藻为代表,研究了硅藻生长条件（pH值、氮浓度、硅浓度、收获时间）对其富集油脂的影响规律和促进机理,发现在缺硅缺氮条件下适当延长收获时间能够显著提高油脂含量,纤细角毛藻的油脂含量和产油能力明显高于新月菱形藻。当培养基中硅浓度（Na2SiO3.9H2O）由200 mg/L降低到0、氮浓度（NaNO3）由12.0 mmol/L降低到0.5 mmol/L、收获时间由8 d延长到32 d时,纤细角毛藻的干燥生物质中油脂含量由13.25%提高到31.74%（达到2.4倍）,细胞产油能力达到39.62 mg/L。     

分散性多糖分散绿藻Chroococcidiorella tianjinensis促进其生长和脂类合成的研究北大核心CSCD

微藻是生产生物柴油的重要原料,其培养过程中需要通气和机械搅拌使藻细胞分散,由此提高了培养成本。为降低培养成本,文章采用分散性多糖(DPS)静置培养绿藻。实验结果表明:浓度为0.3 g/L的DPS即能使藻细胞浓度为3 g/L的绿藻培养液均匀分散,使绿藻的生物量和脂类产量比不添加DPS时分别提高49.30%和81.18%;在DPS浓度为0.3 g/L的基础上添加葡萄糖、乙酸钠和碳酸氢钠3种碳源能够进一步促进绿藻的生长,3种碳源的最佳添加浓度分别为30,3.5,1 g/L;在3种碳源的最佳添加浓度下,与不添加碳源添加DPS的培养相比,绿藻的生物量分别提高了122.36%,57.88%和22.55%,脂类含量分别提高了18.00%,23.09%和10.44%,且适合生产优质生物柴油的不饱和脂肪酸C18-0和C18-1的含量也显著提高。     

菱形藻同时自养和异养提高油脂产率的研究

为了提高菱形藻Nitzschia ZJU2的油脂产率,采用酵母提取物和尿素等有机氮源配合碳源进行同时自养和异养(兼养),优化调控碳氮成分等可显著提高油脂产率。当碳源葡萄糖浓度逐渐增至10 g/L时,油脂产率达到峰值,继续增大葡萄糖浓度反而会导致油脂产率减小;有机氮源优于无机氮源,当酵母提取物浓度达到1.5 g/L时油脂产率最高为164.50 mg/(L·d),达到异养的3倍和自养的8倍。兼养油脂中C16~C19脂肪酸比例(达到89.13%)高于异养和自养,不饱和脂肪酸含量较低,适合制取生物柴油。     

戊糖发酵产油酵母菌的筛选及油脂组成分析

从土壤中筛选到一株能够转化戊糖的高产油脂酵母菌株LY17,该菌株在以木糖为唯一碳源的限氮培养基中进行发酵时,菌体油脂含量为35.06%,油脂产量达到4.73 g/L.常规鉴定和26S rDNA D1/D2区域序列分析表明,菌株LY17属于胶红酵母(Rhodotorula mucilaginosa).脂肪酸组成分析结果表明,菌株LY17以木糖为碳源发酵时,菌体内积累的油脂富含饱和及低度不饱和长链脂肪酸,其中油酸、亚油酸和棕榈酸之和占总脂肪酸组成的90%以上,脂肪酸组成分布类似于常见的植物油.     

真菌Simplicillium lanosoniveum DT06对雨生红球藻生长与脂类合成的影响

文章将雨生红球藻与抗生素合成真菌Simplicillium lanosoniveum DT06在不灭菌条件下混合培养（NM）以促进微藻脂类和虾青素的合成。实验结果表明：与灭菌单独培养（AH）和不灭菌单独培养（NH）的雨生红球藻相比,NM的雨生红球藻生物量（2.45 g/L）分别提高了56%和119%,脂类产量（0.837 g/L）分别提高了112.4%和279%,虾青素产量（88.84 mg/L）分别提高了74%和175%;平均生长速率[194.2 mg/（L·d）]分别提高了60.8%和133.1%,平均比生长速率（0.25 d-1）分别提高了19%和31.6%;平均脂类合成速率[69.75mg/（L·d）]分别提高了112.5%和278.66%,平均脂类比合成速率[28.47 mg/（g·d）]分别提高了36.15%和97%;NM的雨生红球藻细胞中适合生产生物柴油的C16～C18脂肪酸的含量达到了83.19%。     

海藻生物燃料产业化开发的进展

海藻种类多样、光合作用效率高、生长周期短、生物产量高、自身合成油脂能力强,同时还能大量吸收CO2,是制备生物柴油最佳的生物质原料之一。国内外对海藻生物燃料技术的研发均取得一定成果。海藻生物柴油的生产过程主要包括海藻大规模培养、海藻油萃取、酯交换反应、生物柴油后处理4个步骤,而最重要的是海藻的大规模培养。光生物反应器已成为高效、快速、大量培养藻类的关键没备,其一般分为开放式和封闭式两种。AlgaeLink NV公司的海藻光生物反应器是目前世界上唯一已商业化的小型装置。我国企业采用自主研发的反应器装置,通过对环境条件因素进行控制,在技术上已达到海藻含油率40％,日产量1～1．4kg／m^3。当海藻含油率达到60％,日产量平均达到3kg／m^3以上时,海藻生物柴油的生产成本将接近石油柴油的批发价,海藻生物柴油产业将成为一个新兴的替代能源产业。     

Culture of microalgal strains isolated from natural habitats in Thailand in various enriched media

Six freshwater microalgal strains in the class of Chlorophyceae, including Chlorococcum humicola, Didymocystis bicellularis, Monoraphidium contortum, Oocystis parva, Sphaerocystis sp., and Scenedesmus acutus were isolated from natural habitats in Thailand. The six strains were compared for their biomass yield, lipid content, and lipid productivity in four enriched culture media in batch mode. Significant differences were found across algal strains and culture media. The best strain was found to be C. humicola, which had the highest biomass yield of 0.113 g/l/d (in Kuhl medium), the highest lipid content of 45.94% (in BG-11 medium), and the highest lipid yield of 0.033 g/l/d (in 3NBBM medium). The 3NBBM medium, which has the lowest nitrogen concentration among the four culture media, was considered the optimal culture medium for C. humicola for lipid production. The fatty acid profile of C. humicola was also found to be affected by the culture medium. More oleic acid (C18:1) but less linolenic acid (C18:3) was accumulated in BG-11 and 3NBBM than in Kuhl and N-8 media. Lipid profiles of C. humicola were comparable to palm oil in the percentage of palmitic acid and the total amount of saturated fatty acids; however, C. humicola made more poly-unsaturated fatty acids such as linoleic (C18:2) and linolenic (C18:3) acids than oil palms. Lipids from C. humicola were believed to be acceptable for biodiesel production.     

Characterization and transesterification of fresh water microalgal oil

In the present investigation bulk algal biomass was collected from different natural water bodies of Himachal Pradesh, India. Maximum oil content of consortia was estimated at 3.7% and major fatty acids were oleic acid (18:1), palmitic acid (16:0), linoleic acid (18:2), and palmitoliec acid (16:1), which are the main constituents of biodiesel. Viscosity of algae oil was found to be high and transesterification was done by basic, microwave-, and ultrasonication-assisted methods. Maximum conversion from algal oil to fatty acid methyl esters was obtained by ultrasonication-assisted transesterification (71.5%), whereas microwave-assisted and basic transesterification was 58.6 and 51.3%, respectively.     

Growth and lipid accumulation properties of a freshwater microalga, Chlorella ellipsoidea YJ1, in domestic secondary effluents

The combination of microalga-based biodiesel production and wastewater treatment is a promising approach to solve problems related to the energy crisis as well as eutrophication in bodies of water. A freshwater microalga, Chlorella ellipsoidea YJ1, with a high capacity for biomass production and lipid accumulation in secondary effluent was isolated. C. ellipsoidea YJ1 could achieve a biomass of 425 mg L⁻¹ (dry weight) in domestic secondary effluent treated with activated sludge technology; and the lipid content per unit of algal biomass was as high as 43% (w/w) in this condition. The lipid growth rate of C. ellipsoidea YJ1 in domestic secondary effluents could attain 11.4 mg/L. Furthermore, after the cultivation of C. ellipsoidea YJ1, the removal efficiencies of nitrogen and phosphorus from the secondary effluent studied in this paper were more than 99% and 90%, respectively. Logistic and Monod models were used successfully to simulate the growth of C. ellipsoidea YJ1, and its maximum biomass and maximum population growth rate under different initial concentrations of nitrogen and phosphorus could be simulated and predicted using the models. .     

Lipid accumulation in the new oleaginous yeast Debaryomyces etchellsii correlates with ascosporogenesis

The growth characteristics, lipid accumulation and composition during the life cycle of a newly isolated strain of Debaryomyces etchellsii were studied under nitrogen limiting conditions. This yeast, grown in batch flask or bioreactor cultures, reproduced asexually by buds when nitrogen was available in the growth medium, or sexually by ascospores after nitrogen exhaustion, producing more than 7 g L⁻¹ biomass. During ascosporogenesis, an important increase in the cellular lipid content in dry cell mass occurred, i.e. from a mass fraction of 11.9% in the vegetative phase to 22.4%, in the ascosporogenic phase. During transition of D. etchellsii from batch to continuous cultures using dilution rates 0.026 and 0.019 h⁻¹, a shift from sexual to asexual reproduction was observed. At 0.019 h⁻¹, few pseudomycelia were also formed. The yeast synthesized lipids containing long chain fatty acids (mainly C16 and C18). Budded cells at steady-states contained only 8.6–9.3 % of lipids mass fraction per dry cell mass that were composed of oleic and linoleic acids and, to a lesser extent, of palmitic and palmitoleic acids. Neutral lipids were the major fraction represented 61.8–66.1%, of total lipids followed by phospholipids, which was the only fraction in which linoleic acid predominated over oleic acid.     

Characterization of microalgal species isolated from fresh water bodies as a potential source for biodiesel production

Due to increasing oil prices and climate change concerns, biodiesel has gained attention as an alternative energy source. Biodiesel derived from microalgae is a potentially renewable and carbon–neutral alternative to petroleum fuels. One of the most important decisions in obtaining oil from microalgae is the choice of algal species to use. Eight microalgae from a total of 33 isolated cultures were selected based on their morphology and ease of cultivation. Five cultures were isolated from river and identified as strains of Scenedesmus obliquus YSR01, Nitzschia cf. pusilla YSR02, Chlorella ellipsoidea YSR03, S. obliquus YSR04, and S. obliquus YSR05, and three were isolated from wastewater and identified as S. obliquus YSW06, Micractinium pusillum YSW07, and Ourococcus multisporus YSW08, based on LSU rDNA (D1-D2) and ITS sequence analyses. S. obliquus YSR01 reached a growth rate of 1.68 ± 0.28 day⁻¹ at 680_nm and a biomass concentration of 1.57 ± 0.67 g dwt L⁻¹, with a high lipid content of 58 ± 1.5%. Under similar environmental conditions, M. pusillum reached a growth rate of 2.3 ± 0.55 day⁻¹ and a biomass concentration of 2.28 ± 0.16 g dwt L⁻¹, with a relatively low lipid content of 24 ± 0.5% w/w. The fatty acid compositions of the studied species were mainly myristic, palmitic, palmitoleic, oleic, linoleic, g-linolenic, and linolenic acids. Our results suggest that S. obliquus YSR01 can be a possible candidate species for producing oils for biodiesel, based on its high lipid and oleic acid contents.     

Characterization and identification of lipid-producing microalgae species isolated from a freshwater lake

Microalgal lipids are the oils of the future for sustainable biodiesel production. One of the most important decisions in obtaining oil from microalgae is the choice of species. A total of 45 algal cultures were isolated from a freshwater lake at Wonju, South Korea. Five microalgal isolates were selected based on their morphology and ease of cultivation under our test conditions. These cultures were identified as strains of Scenedesmus obliquus YSL02, Chlamydomonas pitschmannii YSL03, Chlorella vulgaris YSL04, S. obliquus YSL05, and Chlamydomonas mexicana YSL07 based on microscopic examination and LSU rDNA (D1-D2) sequence analysis. S. obliquus YSL02 reached a higher biomass concentration (1.84 ± 0.30 g L⁻¹) with a lower lipid content (29% w/w), than did Chla. pitschmannii YSL03 (maximum biomass concentration of 1.04 ± 0.09 with a 51% lipid content). Our results suggest that Chla. pitschmannii YSL03 is appropriate for producing biodiesel based on its high lipid content and oleic acid proportion.     

Isolation and identification by 18S rDNA sequence of high lipid potential microalgal species for fuel production in Hainan Dao

To exploit indigenous microalgal species with the potential for biodiesel production, 101 algal cultures were isolated from partial waters in Hainan province. Eight cultures were selected based on their high biomass, high lipid content and ease of cultivation, then identified based on morphology and 18S rDNA sequence analysis. These isolates were identified as Tetranephris brasiliensis DL12, Ankistrodesmus gracilis DL25, Ankistrodesmus sp. CJ02, Desmodesmus subspicatus WC01, A. gracilis CJ09, Chlorella vulgaris CJ15, Desmodesmus sp. WC08, Chlorella sorokiniana XS04, respectively. Desmodesmus sp. WC08 reached the highest biomass concentration (2.32 g L⁻¹) with the lipid content of 31.30%. Higher lipid content of 47.90% and 47.39% were gained by A. gracilis CJ09 and C. vulgaris CJ15, respectively. However, C. vulgaris CJ15 and Desmodesmus sp. WC08 had higher lipid productivity (117.37 mg L⁻¹ d⁻¹and 115.73 mg L⁻¹ d⁻¹, respectively) in terms of comprehensive consideration. The fatty acid compositions of these microalgal species were mainly palmitic, palmitoleic, stearic, oleic with GC–MS (gas chromatography–mass spectrometer) analysis. A. gracilis CJ09, T. brasiliensis DL12, A. gracilis DL25 and Desmodesmus sp. WC08 had the higher oleic acid content (over 50% of the total fatty acids) than the others. The results suggest that marine microalgae strain Desmodesmus sp. WC08 can be the most appropriate candidate for producing oil for biodiesel, based on its higher biomass productivity, lipid productivity and fatty acid profile.     

Bioenergy potential of duckweed (Lemna gibba L.) biomass

This work illustrates the bioenergy potential of Lemna gibba cultivated on urban wastewater. A reactor (25 L) was established and changes in wastewater and duckweed characteristics were estimated at the end. The reactor showed relative growth rates (RGRs) of 7.47 g/m²d, 10.6 g/m²d, and 13.63 g/m²d after the 1st, 2nd, and 3rd weeks with chemical yield rate (g/m² d) of starch, protein, and lipid of 4.96, 7.68, and 1.90, respectively. The proximate analysis showed 10.03% moisture, 13.23% ash content, 63.96% volatile matter, and 14.73% fixed carbon. The elemental composition (%) of biomass was as follows: C = 41.67, H = 3.57, N = 3.67, S = 0.83, and O = 32.83. The dried biomass showed a high content (%) of energy molecules: total sugar (38.0), starch (24.5), and lipid (9.3). Gas chromatography of the extracted lipid presented high contents of C16:0-palmitic acid (37.68%), C18:2-linoleic acid (18.11%), and C18:3-linolenic acid (33.76%) in duckweed. Results suggested the potential of Lemna as feedstock for renewable energy operations.     

以市政污水为底物的微藻油脂积累和碳流分析

微藻培养的高成本阻碍了微藻生物柴油的工业化推广。文章以市政污水作为Chlorella vulgaris的培养基,分别在水力停留时间(HRT)24,48,96 h和间歇运行时对其进行培养。随着HRT的增加,C.vulgaris在系统生物群落中所占的比例增大,而且细胞密度和脂含量也分别由HRT 24 h时的0.088 g/L和8.4%提高到间歇时的0.164 g/L和14.3%。HRT对废水处理效果的影响较小,不同HRT时,COD和TP的去除率分别在66.1%~71.1%和37.6%~51.1%,TN的去除率则仅为5.9%~11.2%。对间歇污水处理过程碳元素流动分析表明,污水中的71.1%有机碳被微藻利用,其中94.6%被转化为微藻生物质,其余被代谢为CO2释放,废水中有机碳(COD)转化为微藻油脂的转化率为11.6 mg/(mg.L)。     

Genetic variability and divergence studies in seed and oil parameters of mahua (Madhuca longifolia Koenig) J.F. Macribide accessions

Variability in oil content and seed weight of 37 accessions of mahua (Madhuca longifolia Koenig) J.F. Macribide collected from different part of Tamil Nadu, India were assessed. There were significant differences in 100-seed weight and oil parameters, namely, kernel oil %, palmitic acid, stearic acid, oleic acid and linoleic acid. Maximum seed weight (340 g) was recorded in IC554535 and the least weight (100 g) was recorded in IC554545. Kernel oil ranged from minimum of 44.4% in IC554535 to maximum 61.5% in IC556617. The saturated fatty acid i.e palmitic acid and stearic acid ranged from 11.7-25.9% to 19.1-32.2%, respectively. The oleic acid ranged from 32.9 to 48.7% of the total fatty acid while linoleic acid ranged from 9.4 to 15.4%. High heritability was recorded for all the traits studied. It was maximum for palmitic acid (98.6%) and minimum for linoleic acid (95.8%). The Euclidean pairwise dissimilarities were calculated and clustered by UPGMA based SAHN clustering method. Maximum and minimum Euclidean pairwise dissimilarities observed were 7.01 and 0.46, respectively. All the 37 accessions were grouped into three major clusters. The accessions in cluster II had low palmitic acid and high oleic acid while cluster III had high palmitic acid and low oleic acid content. Normalized Mantel statistics (r = 0.8) and principal component analysis supported cluster analysis. Thus on the basis of present findings it is suggested that hybridization between accessions of cluster II and III will result in wide spectrum of variability in subsequent generations for medicinal, edible applications and biodiesel production.