Nitrogen starvation strategies and photobioreactor design for enhancing lipid content and lipid production of a newly isolated microalga Chlorella vulgaris ESP-31: implications for biofuels

Microalgae are recognized for serving as a sustainable source for biodiesel production. This study investigated the effect of nitrogen starvation strategies and photobioreactor design on the performance of lipid production and of CO(2) fixation of an indigenous microalga Chlorella vulgaris ESP-31. Comparison of single-stage and two-stage nitrogen starvation strategies shows that single-stage cultivation on basal medium with low initial nitrogen source concentration (i.e., 0.313 g/L KNO(3)) was the most effective approach to enhance microalgal lipid production, attaining a lipid productivity of 78 mg/L/d and a lipid content of 55.9%. The lipid productivity of C. vulgaris ESP-31 was further upgraded to 132.4 mg/L/d when it was grown in a vertical tubular photobioreactor with a high surface to volume ratio of 109.3 m(2)/m(3) . The high lipid productivity was also accompanied by fixation of 6.36 g CO(2) during the 10-day photoautotrophic growth with a CO(2) fixation rate of 430 mg/L/d. Analysis of fatty acid composition of the microalgal lipid indicates that over 65% of fatty acids in the microalgal lipid are saturated [i.e., palmitic acid (C16:0) and stearic acid (C18:0)] and monounsaturated [i.e., oleic acid (C18:1)]. This lipid quality is suitable for biodiesel production.     

氧化铝气体分布器应用小球藻培养的研究

光生物反应器设计中,气体分布器对微藻生长有较大的影响,尤其是在鼓泡式光生物反应器中更为显著。实验考察了采用氧化铝烧制的多孔气体分布器的5L鼓泡式光生物反应器中通气速率、CO₂ 浓度对小球藻LICME002生物量、叶绿素含量、油脂积累的影响。对该气体分布器下的CO₂浓度和通气速率对小球藻的作用机理进行了初步的探讨。结果表明,CO₂浓度为3%时,该株微藻生物量、叶绿素、油脂积累的最佳;CO₂浓度超过6%时各项指标显著下降。通过对0.1vvm,0.4vvm,0.7vvm、1.0vvm的通气速条件下的各项指标的分析,确定最佳通气条件为0.4vvm。结论显示,在最佳通气速率和CO₂浓度下,微藻生物量能达到1.52g/L,油脂含量达到31.5%。     

囊状黄丝藻在不同初始氮浓度条件下特殊的油脂积累规律

对不同初始氮浓度条件下囊状黄丝藻(Tribonema utriculosum SAG22.94)的生长状况、油脂含量和脂肪酸组成与含量进行研究。结果显示,囊状黄丝藻在氮浓度为3.0 mmol/L时,获得生物质浓度最高,为6.39 g/L;氮浓度为18.0 mmol/L时获得总脂和总脂肪酸含量最高,分别为细胞干重的44.62%和42.21%;上述3个指标单位体积的产率均在氮浓度3.0 mmol/L时达到最高值,分别为0.538、0.209和0.206 g·L~(-1)·d~(-1)。在4种初始氮浓度条件下,囊状黄丝藻油脂和脂肪酸含量可随着氮浓度增加而增加。脂肪酸含量分析结果显示,该藻的主要脂肪酸为豆蔻酸(C14∶0)、棕榈酸(C16∶0)、棕榈油酸(C16∶1ω7)、花生四烯酸(C20∶4ω6)和二十碳五烯酸(C20∶5ω3,EPA)。其中棕榈油酸含量最高,占总脂肪酸含量的36.53%~50.08%。研究结果表明囊状黄丝藻在不同初始氮浓度条件下具有特殊的油脂积累规律,是一株具有重要应用价值的产油丝状微藻。     

营养盐初始组合浓度对类波氏真眼点藻生长和油脂积累的影响

为了研究培养基中主要营养元素氮、磷、硫初始组合浓度对类波氏真眼点藻(Eustigmatos cf.polyphem D.J.Hibberd)生长、油脂积累和脂肪酸组成的影响,分别以NaNO_3、K_2HPO_4、MgSO_4为氮、磷、硫源,设置不同的营养盐初始组合浓度对其进行培养,采用干重法、重量法、气相色谱分析法、元素分析仪等依次对生物量、总脂、脂肪酸组成和细胞内元素含量进行测定。结果显示,氮、磷、硫三者的初始组合浓度变化对类波氏真眼点藻的生长和油脂积累具有明显的影响,9 mmol/L NaNO_3、0.92 mmol/L K_2HPO_4、0.3 mmol/L MgSO_4营养条件下其生物量达到最大值,为9.19 g/L;低氮、低磷胁迫或二者共同胁迫均促进其油脂积累,但低硫胁迫对油脂的积累影响不大,最大油脂含量出现在3 mmol/L NaNO_3、0.029 mmol/L K_2HPO_4、0.3 mmol/L MgSO_4条件下,为68.7%(DW)。此外,类波氏真眼点藻富含棕榈油酸,占总脂肪酸含量的最大值达60.88%。选择合理的氮、磷、硫初始组合浓度能够有效促进其生长或油脂及棕榈油酸的积累。     

碳源对粉核油球藻生长和脂肪酸组成特性的影响

研究了不同碳源类型（CO2、NaHCO3和葡萄糖）及其浓度对粉核油球藻（Pinguiococcus pyrenoidosus CCMP 2078）生长及脂肪酸组成的影响。结果表明：（1）培养液中适量添加碳源促进了粉核油球藻的生长,三种碳源的适宜添加浓度分别是0.5% CO2,5mmol/L NaHCO3和20g/L葡萄糖,对数生长末期的细胞密度分别是对照的3.10倍、1.47倍和2.78倍;（2）除了低浓度葡萄糖外,其他碳源类型和浓度均降低了TPUFA和EPA占总脂肪酸的比例,提高了TSFA的比例,胞内EPA和TSFA含量均下降;（3）低浓度碳源提高了TSFA和EPA产量。通入0.5% CO2培养的EPA和TSFA产量分别是对照的2.30倍和2.69倍,5mmol/L NaHCO3培养的TSFA产量是对照的1.85倍,5g/L和10g/L葡萄糖培养的EPA和TSFA产量最高分别可达对照的2.11倍和1.58倍。因此,通入低浓度CO2最有利于粉核油球藻的生长以及EPA和饱和脂肪酸的生产,EPA和饱和脂肪酸含量的提高主要是通过生物量的增大来实现的。     

氮源种类及浓度对眼点拟微绿球藻生长密度、油脂产率和二十碳五烯酸含量的影响

氮源是影响微藻生长和油脂积累的重要因素,文中通过单因素试验比较了NaNO3、CO(NH2)2、NH4Cl、CH3COONH4及其浓度对眼点拟微绿球藻生长密度、生长速率、油脂产率、二十碳五烯酸(EPA)含量的影响。结果表明：NH4+更易被眼点拟微绿球藻利用,能更好地促进微藻生长和油脂积累;氮浓度的增加有利于微藻的生长和藻油脂肪酸的去饱和,但不利于微藻油脂的积累。在实验考察的氮源种类和浓度范围内,CH3COONH4是促进眼点拟微绿球藻生长和油脂积累、EPA生成的适宜氮源,其适宜的浓度为5.29 mmol/L。     

Effects of carbon source and light intensity on the growth and total lipid production of three microalgae under different culture conditions

We attempted to enhance the growth and total lipid production of three microalgal species, Isochrysis galbana LB987, Nannochloropsis oculata CCAP849/1, and Dunaliella salina, which are capable of accumulating high content of lipid in cells. Low nitrogen concentration under photoautotrophic conditions stimulated total lipid production, but a decreasing total lipid content and an increasing biomass were observed with increasing nitrogen concentration. Among the different carbon sources tested for heterotrophic cultivation, glucose improved the growth of all three strains. The optimal glucose concentration for growth of I. galbana LB987 and N. oculata CCAP849/1 was 0.02 M, and that of D. salina was 0.05 M. Enhanced growth occurred when they were cultivated under heterotrophic or mixotrophic conditions compared with photoautotrophic conditions. Meanwhile, high total lipid accumulation in cells occurred when they were cultivated under photoautotrophic or mixotrophic conditions. During mixotrophic cultivation, biomass production was not affected significantly by light intensity; however, both chlorophyll concentration and total lipid content increased dramatically with increasing light intensity up to 150 µmol/m²/s. The amount and composition ratio of saturated and unsaturated fatty acids in cells were different from each other depending on both species and light intensity. The highest accumulation of total fatty acid (C16–C18) among the three strains was found from cells of N. oculata CCAP849/1, which indicates that this species can be used as a source for production of biodiesel.     

Norepinephrine-stimulated fatty-acid release and oxygen consumption in isolated hamster brown-fat cells. Influence of buffers, albumin, insulin and mitochondrial inhibitors.

Brown fat cells isolated from adult golden hamsters have earlier been found to respond to addition of the physiological agonist norepinephrine with an increased rate of oxygen consumption and with fatty acid release. Working with these cells, we found the following. 1. The presence of albumin in the incubation medium (phosphate buffer) increases norepinephrine-induced fatty acid release and tends to stabilize the rate of oxygen consumption; bubbling of phosphate buffer with 5% CO2 in air has only a slight effect on fatty acid release. 2. In the presence of albumin, the norepinephrine-induced rate of oxygen consumption is also stable in bicarbonate buffer; it is higher than in the phosphate + CO2 buffer and the brown fat cells have a higher sensitivity to norepinephrine. 3. 20 mM phosphate (as e.g. present in a phosphate buffer) inhibits both fatty acid release and oxygen consumption. 4. Insulin inhibits the rate of oxygen consumption, but only at suboptimal concentrations of norepinephrine. 5. Atractylate inhibits submaximal norepinephrine-induced respiration, indicating that some oxidative phosphorylation takes place in norepinephrine-stimulated brown fat cells. 6. Fatty acid export from brown fat should be regarded as physiologically important.     

光强及氮浓度对丝状绿藻双星藻生长及生化组成的影响

[背景]环境因子和营养因子对微藻的生长和生化组成都有显著的影响,其中光强和氮浓度是最重要的两个条件。[目的]研究不同光强和初始氮浓度对丝状绿藻-双星藻(Zygnema sp.)生长及生化组成的影响。[方法]采用改良的BBM培养基,设置了两组光强[100μmol/(m²·s)和300μmol/(m²·s)]和6种初始氮浓度(3、6、9、12、15和18 mmol/L)在柱状光生物反应器中对双星藻进行培养。[结果]在高光强条件下[300μmol/(m²·s)],12 mmol/L初始氮浓度最有利于双星藻生物质的积累,其最高生物量可以达到6.60 g/L,而初始低氮浓度(3 mmol/L)则促进了油脂和脂肪酸的积累,油脂最高含量占干重的32.13%,且脂肪酸组成主要包括棕榈酸(C_16:0)、油酸(C_18:1)、亚油酸(C_18:2)和亚麻酸(C_18:3),其中油酸含量最高达到总脂肪酸含量的55.01%;在低光强条件下[100μmol/(m     

Variation of photoautotrophic fatty acid production from a highly CO2 tolerant alga,Chlorococcum littorale,with inorganic carbon over narrow ranges of pH

Photoautotrophic fatty acid production of a highly CO₂‐tolerant green alga Chlorococcum littorale in the presence of inorganic carbon at 295 K and light intensity of 170 µmol‐photon m^?2 s^?1 was investigated. CO₂ concentration in the bubbling gas was adjusted by mixing pure gas components of CO₂ and N₂ to avoid photorespiration and β‐oxidation of fatty acids under O₂ surrounding conditions. Maximum content of total fatty acid showed pH‐dependence after nitrate depletion of the culture media and increased with the corresponding inorganic carbon ratio. Namely, [HCO₃^?]/([CO₂]+n[ ]) ratio in the culture media was found to be a controlling factor for photoautotrophic fatty acid production after the nitrate limitation. At a CO₂ concentration of 5% (vol/vol) and a pH of 6.7, the fatty acid content was 47.8 wt % (dry basis) at its maximum that is comparable with land plant seed oils. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1053–1057, 2015     

Optimization of growth and fatty acid composition of a unicellular marine picoplankton,Nannochloropsis sp., with enriched carbon sources

A unicellular marine picoplankton, Nannochloropsis sp., was grown under CO₂-enriched photoautotrophic or/and acetate-added mixotrophic conditions. Photoautotrophic conditions with enriched CO₂ of 2800 l CO₂ l^–1 and aeration gave the highest biomass yield (634 mg dry wt l^–1), the highest total lipid content (9% of dry wt), total fatty acids (64 mg g^–1 dry wt), polyunsaturated fatty acids (35% total fatty acids) and eicosapentaenoic acid (EPA, 20:53) (16 mg g^–1 dry wt or 25% of total fatty acids). Mixotrophic cultures gave a greater protein content but less carbohydrates. Adding sodium acetate (2 mM) decreased the amounts of the total fatty acids and EPA. Elevation of CO₂ in photoautotrophic culture thus enhances growth and raises the production of EPA in Nannochloropsis sp.     

Lipid accumulation in an oleaginous yeast (Candida 107) growing on glucose in single-stage continuous culture.

Lipid accumulation of Candida 107, grown at dilution rates from 0.03 to the maximum of 0.21/h, with carbon, nitrogen, phosphate, and magnesium limitations in a chemostat, was maximal at about 40% (wt/wt) with nitrogen-limited medium at a dilution rate of 0.06/h, giving an efficiency of substrate conversion of 22 g of lipid per g of glucose consumed. At higher dilution rates the lipid content decreased. With carbon-limited growth, the highest lipid content (14%, wt/wt) was at the maximum dilution rate. High lipid contents also occurred with phosphate + nitrogen as double limitations of growth, with the lipid content of the yeast (about 35%, wt/wt) continuing to be near maximum at dilution rates also near maximum (0.17/h), thus giving the highest specific rate of lipid formation of any growth conditions (0.59 g of lipid/g of yeast per h). However, the efficiency of substrate utilization was only 5.2 g of lipid formed per 100 g of glucose consumed. The composition of the fatty acyl residues within the lipid remained constant over many weeks if the steady-state conditions remained unchanged. With carbon-limited growth, the degree of unsaturation of the fatty acids markedly decreased as the dilution rate was increased, but with nitrogen limitation the reverse trend was seen. In all cases, linoleic and oleic acids were the principal fatty acyl residues affected, and their relative proportions always varied in opposite directions. When magnesium was a limiting nutrient, there was a considerable increase in the proportion of myristic acid produced within the lipid. Neutral lipids (predominantly triglycerides) varied from 66 to 92% of the total lipid from carbon- and nitrogen-limited growth; phospholipids (varying from 2 to 25%) were highest in nitrogen-limited growth. The fatty acyl residues within each lipid fraction showed the same variations with changing growth rates.     

富碳培养对海洋富油微藻油脂积累特性的影响

实验针对三株海洋富油微藻:球等鞭金藻（Isochrysis galbana CCMM5001）、一种等鞭金藻（Isochrysis sp. CCMM5002）和一种微拟球藻（Nannochloropsis sp. CCMM7001）,研究了它们在通入0.03%（空气）、5%、10%三个浓度CO2培养条件下的生长特性,同时考察了其总油脂及中性脂的累积情况。结果显示,富碳培养有利于这三株海洋微藻的生长,但最适生长的CO2浓度不同。球等鞭金藻（Isochrysis galbana CCMM5001）和等鞭金藻（Isochrysis sp. CCMM5002）在通入10% CO2时具有最大产率,分别达到（182.287.07） mg/（Ld）和（164.227.10） mg/（Ld）,而微拟球藻在通入5%时具有最大产率,达到（122.251.17） mg/（Ld）,随着CO2浓度的增加,三株海洋微藻的总脂含量和中性脂含量有明显提高。在通入10% CO2条件下,球等鞭金藻（Isochrysis galbana CCMM5001）、等鞭金藻（Isochrysis sp. CCMM5002）和微拟球藻（Nannochloropsis sp. CCMM7001）的总脂含量分别达到（45.154.03）%、（47.151.20）%和（41.201.69）%;从中性脂的累积规律来看,三株藻均在平台期的累积达到最大,脂肪酸分析结果表明三株藻种适合制备生物柴油的C14-C18系脂肪酸相对含量在不同CO2条件下基本保持不变,维持在90%左右。实验结果显示,研究的藻株作为富油高固碳优良藻株,具备用于海洋生物质能耦合CO2减排开发的潜力。       

黄腐酸对单针藻生长和油脂含量的影响

为了研究不同浓度的黄腐酸对单针藻Monoraphidium sp.FXY-10细胞生长、油脂合成的影响,研究于Kuh1培养基中添加4种不同浓度的黄腐酸(40、80、120和160 mg/L),优化出异养培养条件下最适合藻细胞生长的黄腐酸浓度;并采用黄腐酸与异养-自养两步培养联用的方法提高细胞量和油脂含量,自养培养时在培养基中添加5、25、125和625 mg/L的黄腐酸诱导油脂的合成。结果表明,80 mg/L的黄腐酸对细胞生长的促进作用最显著,细胞量可达6.4 g/L,为对照组的1.5倍。黄腐酸的浓度增加至160 mg/L,藻细胞的生长受到明显的抑制。自养培养阶段,添加25 mg/L的黄腐酸能显著地提高藻细胞的油脂含量,其油脂含量从30.78%增加至54.65%。黄腐酸对于单针藻的生长和油脂合成具有明显的促进作用,黄腐酸与两步法联用在提高微藻细胞量和油脂含量方面具有较好的应用前景。     

Influence of CO2 on growth and hydrocarbon production in Botryococcus braunii

Botryococcus braunii is a green colonial fresh water microalga and it is recognized as one of the renewable resources for production of liquid hydrocarbons. CFTRI-Bb-1 and CFTRI-Bb-2 have been reported for the first time and their performance with regard to growth and biochemical profile is presented here. The present study focused on effect of carbon dioxide (CO2) on biomass, hydrocarbon, carbohydrate production, fatty acid profile, and carotenoid content in various species of B. braunii (LB-572, SAG 30.81, MCRC-Bb, N-836, CFTRI-Bb-1, and CFTRI-Bb-2) at 0.5, 1.0, and 2.0% (v/v) levels using a two-tier flask. CO2 at 2.0% (v/v) level enhanced growth of the organism, and a two-fold increase in biomass and carotenoid contents was observed in all the B. braunii strains studied compared with control culture (without CO2 supplementation). At 1% and 2% (v/v) CO2 concentrations, palmitic acid and oleic acid levels increased by 2.5 to 3 folds in one of the strains of B. braunii (LB-572). Hydrocarbon content was found to be above 20% at 2% CO2 level in the B. braunii LB-572, CFTRI-Bb-2, CFTRI-Bb-1, and N-836 strains, whereas it was less than 20% in the SAG 30.81 and MCRC-Bb strains compared with control culture. This culture methodology will provide information on CO2 requirement for growth of algae and metabolite production. B. braunii spp. can be grown at the tested levels of CO2 concentration without much influence on culture pH.     

Elevated atmospheric CO(2) concentration and diurnal cycle induce changes in lipid composition in Arabidopsis thaliana

Few studies regarding the effects of elevated atmospheric CO(2) concentrations on plant lipid metabolism have been carried out. Here, the effects of elevated CO(2) concentration on lipid composition in mature seeds and in leaves during the diurnal cycle of Arabidopsis thaliana were investigated. Plants were grown in controlled climate chambers at elevated (800 ppm) and ambient CO(2) concentrations. Lipids were extracted and characterized using thin layer chromatography (TLC) and gas liquid chromatography. The fatty acid profile of total leaf lipids showed large diurnal variations. However, the elevated CO(2) concentration did not induce any significant differences in the diurnal pattern compared with the ambient concentration. The major chloroplast lipids monogalactosyldiacylglycerol (MGDG) and phosphatidylglycerol (PG) were decreased at elevated CO(2) in favour of phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Elevated CO(2) produced a 25% lower ratio of 16:1trans to 16:0 in PG compared with the ambient concentration. With good nutrient supply, growth at elevated CO(2) did not significantly affect single seed weight, total seed mass, oil yield per seed, or the fatty acid profile of the seeds. This study has shown that elevated CO(2) induced changes in leaf lipid composition in A. thaliana, whereas seed lipids were unaffected.     

碳源、氮源对异养单针藻Monoraphidium sp. FXY-10油脂积累和脂肪酸组成的影响

研究了碳源与氮源对单针藻Monoraphidium sp. FXY-10异养培养的影响。以BG-11为基础培养基,通过添加不同类型、浓度梯度碳源和氮源,比较分析微藻生物量、油脂积累以及脂肪酸组成。结果表明,以葡萄糖作碳源,硝酸钠为氮源,微藻细胞积累的油脂是理想的生物柴油制备原料。硝酸钠浓度分别为1.00、3.00和5.00 g/L时,对油脂产量影响不显著(P>0.05)。葡萄糖浓度为10.00 g/L,硝酸钠为氮源油脂产量达到实验最高值0.84 g/L,其油脂脂肪酸组成主要由C16:0和C18:1等短链饱和脂肪酸和单不饱和脂肪酸组成,不饱和度值(DU)为61.98,相对偏低。     

Efficient lipid production with Trichosporon fermentans and its use for biodiesel preparation

Effects of medium components and culture conditions on biomass and lipid production of Trichosporon fermentans were studied. The optimal nitrogen source, carbon source and C/N molar ratio were peptone, glucose and 163, respectively. The favorable initial pH of the medium and temperature were 6.5 and 25 degrees C. Under the optimized conditions, a biomass of 28.1 g/l and a lipid content of 62.4% could be achieved after culture for 7 days, which were much higher than the original values (19.4 g/l and 50.8%) and the results reported by other groups. T. fermentans could grow well in pretreated waste molasses and a lipid yield of 12.8 g/l could be achieved with waste molasses of 15% total sugar concentration (w/v) at pH 6.0, representing the best result with oleaginous microorganisms on agro-industrial residues. Addition of various sugars to the pretreated molasses could efficiently enhance the accumulation of lipid and the lipid content reached as high as above 50%. Similar to vegetable oils, the lipid mainly contains palmitic acid, stearic acid, oleic acid and linoleic acid and the unsaturated fatty acids amount to about 64% of the total fatty acids. The microbial oil with an acid value of 5.6 mg KOH/g was transesterified to biodiesel by base catalysis after removal of free fatty acids and a high methyl ester yield of 92% was obtained.     

高、低氮浓度对2株真眼点藻的生长和油脂积累的影响

【目的】研究氮浓度对真眼点藻纲(Eustigmatophyceae)的2株高产油微藻大真眼点藻(Eustigmatos magnus,EM)和波氏真眼点藻(Eustigmatos polyphem,EP)的细胞形态、生长、总脂含量、脂质组成和脂肪酸组成与含量的时序变化规律。【方法】利用高氮(18.0 mmol/L NO3?-N)和低氮(3.6 mmol/L NO3?-N)浓度培养微藻。【结果】形态观察结果表明,大真眼点藻(E. magnus)和波氏真眼点藻(E. polyphem)营养细胞具有1个周生的裂叶状叶绿体,细胞质中有液泡,内含能够振动的颗粒物,以及一个较为明显的红色色素体;生殖方式通过形成2个D形或4个四角形的似亲孢子;随着培养周期的延伸和营养盐的消耗,细胞中油体逐步形成,其数量不断增加,体积不断增大。实验结果表明,初始氮浓度对2种微藻的总脂积累及生长均有显著影响(P<0.05),低氮浓度下2种微藻的生物质浓度分别为9.0 g/L和8.5 g/L,均低于高氮浓度下的生物质浓度。而低氮浓度下2种微藻的总脂、中性脂和总脂肪酸的含量以及总脂、中性脂与总脂肪酸的单位体积产率均明显高于高氮浓度组,其最高值分别为：59.10%、51.90%、46.95%和0.28、0.24、0.22 g/(L·d) (EM);64.20%、56.80%、50.01%和0.32、0.28、0.25 g/(L·d) (EP)。脂肪酸分析结果表明,两种微藻的脂肪酸主要成分均为棕榈酸(C16:0)、棕榈油酸(C16:1)、油酸(C18:1)和二十碳五烯酸(C20:5,EPA),四者的总含量(占总脂肪酸)分别达到85.83%和85.48%,其中棕榈油酸的含量最高。【结论】低氮浓度胁迫有利于大真眼点藻和波氏真眼点藻细胞内油脂的积累,两种微藻均为适合于生产生物柴油的油脂生产藻株。     

News & Notes: The Effect of Ethanol and Oxygen on the Growth of Zymomonas mobilis and the Levels of Hopanoids and Other Membrane Lipids

Zymomonas mobilis (ATCC 29191) was grown either aerobically or anaerobically in the presence of 2% (wt/vol) glucose and 0, 3, or 6% (vol/vol) ethanol. The rates of growth and the composition of hopanoids, cellular fatty acids, and other lipids in the bacterial membranes were quantitatively analyzed. The bacterium grew in the presence of 3% and 6% ethanol and was more ethanol tolerant when grown anaerobically. In the absence of ethanol, hopanoids comprised about 30% (by mass) of the total cellular lipids. Addition of ethanol to the media caused complex changes in the levels of hopanoids and other lipids. However, there was not a significant increase in any of the hopanoid lipid classes as ethanol concentration was increased. As previously reported, vaccenic acid was the most abundant fatty acid in the lipids of Z. mobilis, and its high constitutive levels were unaffected by the variations in ethanol and oxygen concentrations. A cyclopropane fatty acid accounted for 2.6–6.4 wt % of the total fatty acids in all treatments. Received: 12 November 1996 / Accepted: 25 February 1997