不同亚临界溶剂从微拟球藻湿藻泥中提取油脂

以微拟球藻(Nannochlorsis sp.)湿藻泥为原料,研究了亚临界乙醇、亚临界乙醇-正己烷共溶剂及硫酸辅助亚临界乙醇-正己烷共溶剂3种萃取体系对微藻油脂提取的影响. 结果表明,亚临界乙醇-正己烷比亚临界乙醇对湿藻细胞有更高的油脂萃取率和低的溶剂用量,加入少量硫酸可进一步提高油脂的提取率、降低溶剂用量. 微拟球藻湿藻泥(含水约70%)优化提取条件为,正己烷/乙醇体积比3:1,液固比(溶剂/藻细胞干重)7 mL/g,加入藻细胞干重6%的硫酸,1.5 MPa下90℃萃取30 min,在此条件下油脂提取率可达90%以上. 3种萃取体系获得的微藻油脂均以甘油三酯为主,甘油三酯的脂肪酸主要为C16:0, C18:1和C16:1,其中硫酸辅助亚临界共溶剂萃取的微藻油脂中甘油三酯含量最高,约占总脂的86%以上.     

从雨声红球藻中提取虾青素的皂化工艺优化

目的:优选从雨声红球藻提取虾青素的皂化工艺。方法:以虾青素的提取得率为考察目标,通过单因素法、正交设计法优化从雨声红球藻提取虾青素的皂化工艺。结果:筛选最佳皂化工艺为是加入10倍雨生红球藻量的4%KOH无水乙醇溶液,在10℃下皂化10min。结论:筛选出来的皂化工艺稳定可行、操作简单。     

利用雨生红球藻生产虾青素的小试研究

以BG11为基本培养基,小试研究了环境因子的调控对雨生红球藻(Haematoccus pluvialis,FACHB-712)生长和虾青素积累的影响。通过单因子实验改变营养方式、pH值、温度、光照时间和光照强度,测定藻液光密度和虾青素含量等指标。结果表明:添加1g/L葡萄糖作为碳源可明显提高藻种生物量;pH=8.0左右,22～27℃,高光强(200μmol·m-2·s-1)连续光照(24h)的生长条件最适合雨生红球藻游动细胞的增殖,可以作为大规模培养雨生红球藻生产虾青素的实验依据。     

碳和氮代谢被抑制诱导雨生红球藻细胞内虾青素的合成

为研究雨生红球藻(Haematococcus pluvialis)合成虾青素的机理,文中分析了不同诱导条件下藻细胞内氮和碳代谢的变化。结果表明:强光照(HL)、添加乙酸钠(AA)、缺氮(NF)和缺磷(PF)都直接或间接地影响了雨生红球藻细胞内1,5-二磷酸核酮糖羧化酶(Rub isco)和硝酸还原酶(NR)的活性,导致2种酶的活性大幅度下降。只有当Rub isco和NR的活性降到非常低的水平时,藻细胞才开始合成虾青素。与此相反,对照(CK)中这2种酶的活性一直较高,但细胞内没有虾青素积累。由于Rub isco和NR是雨生红球藻碳代谢和氮代谢的关键酶,因此碳和氮代谢被抑制是诱导雨生红球藻合成虾青素的原因。     

微藻食用油脂浸提溶剂的选择与分析

分别向微藻中加入6种常用溶剂,冰浴超声处理15 min,振荡浸提8 h,提取微藻中的油脂,考察了溶剂的浸提能力.结果表明,浸提干藻粉与湿藻泥中的油脂可选择不同溶剂,用正己烷浸提干藻粉中油脂,提取率可达71.52%,其中中性脂占75.86%,维生素含量E为1.63%,提取油脂后的藻渣中蛋白质、叶绿素和糖类的保留率分别为55.92%,61.33%和78.35%,营养成分保留率较高;用正己烷/乙醇混合溶剂浸提湿藻泥中油脂,提取率可达68.31%,其中中性脂占71.65%,维生素E含量为1.87%,提取油脂后的藻渣中蛋白质、叶绿素和糖类的保留率分别为60.56%,53.27%和80.20%.     

雨生红球藻的新繁殖方式及其藻蓝蛋白的合成

雨生红球藻(Haematococcus pluvialis)是一种能够合成强抗氧化剂-虾青素的单细胞绿藻,然而由于其生长速率缓慢,制约了虾青素产量的提高。在对雨生红球藻细胞周期的研究中,首次发现了雨生红球藻在高温和低光照条件下的一种特殊繁殖方式,该繁殖方式比已知的营养繁殖和无性繁殖速度快。繁殖过程中厚壁孢子萌发产生大量的小细胞,并且这些小细胞中含有以前在绿藻中从未发现的捕光色素蛋白—藻蓝蛋白(最大吸收波长λmax=621 nm,最大荧光发射波长λmFax=643 nm)。这一发现对于提高天然虾青素的产量和藻蓝蛋白的生产以及藻类的进化有着重要的意义。     

转光膜在雨生红球藻养殖上的应用

通过对雨生红球藻在不同光质条件下生长的比较,确定了红色光有利于藻生长,进而用2.5 L气升式光照反应器在转光膜及普通PE膜下培养藻进行对比,结果显示雨生红球藻生物量、色素、光合活性等几项生物指标在转光膜条件下明显高于普通PE膜. 在气升式反应器内培养的藻细胞,接种9 d,虾青素含量可达3.57 mg/L,叶绿素浓度达到12.42 mg/L,干重提高8.8%以上.     

超声辅助提取虾青素的工艺优化及动力学研究

以乙醇为溶剂,采用超声辅助方法从新鲜雨生红球藻中提取虾青素,优化工艺参数。首先采用单因素方法研究提取时间、超声功率、料液比对提取得率的影响,然后通过响应面方法优化工艺参数。结果表明提取时间28 min,超声功率87 W,料液比1∶25时,虾青素得率最高,达到(35.93±0.37)mg/g。该最佳条件下的虾青素提取符合二级动力学规律(R²=0.998 9),提取速率与浓度差的平方成正比。该方法制备的虾青素提取液对DPPH和OH的半抑制浓度分别为(16.14±1.58)μg/mL和(0.93±0.18)μg/mL。     

强光照对雨生红球藻合成虾青素的影响

在不同的光照强度下研究了雨生红球藻细胞内虾青素的合成与初级代谢的关系.在强光(HL)和中等强度(ML)的光照条件下,雨生红球藻细胞内1,5-二磷酸核酮糖羧化酶 (Rubisco)和硝酸还原酶(NR)的活性第1天大幅度提高,2天后又迅速下降.与此同时,硝酸盐浓度也快速降低.当虾青素在第4天(HL)和第6天(ML)开始合成时, HL中Rubisco和NR活性以及NO3-浓度分别下降了75.5%,71.5% 和96.2%,而ML中则下降了76.5%,74.7% 和94.3%.相比之下,在低光照(LL)条件下,实验结束时三个指标仅下降了25.9%,29.8% 和56.8%,细胞中没有虾青素积累.结果表明强光提高了Rubisco 和 NR活性,导致硝酸盐浓度迅速降低而最终又抑制了这两种酶的活性,造成雨生红球藻光合作用效率下降即"碳饥饿".在此状态下,为了生存,细胞内合成虾青素的相关基因被激活,藻细胞开始合成并积累虾青素.     

环状芽孢杆菌胞壁溶解酶用于红发夫酵母虾青素提取的研究

采用单因素及均匀实验设计确定了将环状芽孢杆菌胞壁溶解酶用于红发夫酵母破壁提取虾青素的最佳酶作用条件,即粗酶液pH值为5.0,体积为33mL(酶量1603.8U(g(1干酵母),温度37℃,100r(min(1振荡反应16.5h,虾青素的提取率可达到98%以上.通过对不同方法提取所得虾青素的光、热稳定性进行测试,发现酶法提取的虾青素不论是在光照还是在加热条件下均比机械法及酸法破壁提取所得的虾青素稳定.     

Supercritical CO2 extraction of lipids and astaxanthin from Brazilian redspotted shrimp waste (Farfantepenaeus paulensis)

Brazilian redspotted shrimp (Farfantepenaeus paulensis) waste is an important source of carotenoids such as astaxanthin and lipids with a high ω−3 fatty acids content, mainly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In order to establish an efficient and environmental friendly recovery process, the lipids and astaxanthin were extracted from the freeze-dried redspotted shrimp waste (including head, tail and shell) using supercritical carbon dioxide. The effects of the extraction conditions of pressure (200-400 bar) and temperature (40-60 °C) on the global yield (X₀), astaxanthin extraction yield and astaxanthin concentration in the extract were evaluated. It was found that the pressure and temperature showed a very low significant effect on the lipid extraction yield using supercritical CO₂. In comparison with lipid extraction by solvents, maximum efficiency of supercritical fluid extraction achieved 64% of hexane extraction yield. On the other hand, temperature and pressure had significant effects on astaxanthin extraction yield. Thegreatest amount of extract was obtained at 43 °C and 370 bar, with 39% of recovery.     

Evaluating Cell Disruption Strategies for Aqueous Lipid Extraction from Oleaginous Scenedesmus obliquus at High Solid Loadings

Among various renewable energy sources, the production of biofuels derived from algal lipids holds bright prospects. One of the major roadblocks in the successful commercialization of microalgal biofuels is the existing energy‐intensive lipid extraction. In the present investigation, an attempt is made to assess aqueous lipid extraction strategies from oleaginous Scenedesmus obliquus at a high solid loading of 15% (w/v). In this study, four surfactants and five enzymes are evaluated for cell disruption of S. obliquus. It is the first report citing cetyl pyridinium bromide as the most suitable cationic detergent for surfactant‐assisted extraction, with a lipid recovery as high as 31.4%. However, during the evaluation of enzyme‐based cell disruption, neutral protease emerges as the best biocatalyst resulting in a lipid recovery of ≈75%. Total lipid extraction is accomplished using a two solvent system comprising of water‐immiscible ethyl acetate, followed by chloroform addition. The study revalidates the fact that the biochemical composition of Scenedesmus sp. plays a vital role while identifying and formulating an efficient and green process for microalgal cell disruption for enhanced lipid extraction under aqueous conditions. Practical Applications: The results of the present study demonstrate that if the biochemical composition of any oleaginous algal cell wall is known, aqueous enzymatic lipid extraction can be employed rather than taking up the conventional route of drying followed by Soxhlet extraction. The combination of using the cheap sources of enzymes and water‐immiscible green solvents like ethyl acetate can be lucrative downstream procedures for the lipid recovery from wet algal biomass when compared to traditional procedures.     

Extraction of lipids from fermentation biomass using near-critical dimethylether

The extraction of lipids from both wet and dry biomass produced by fermentation has been carried out using near-critical dimethylether (DME) as the extraction solvent. Fermentations were carried out from a shake flask up to a 300 L scale using the microorganism Mortierella alpina, and up to a 20 L scale for Phaffia rhodozyma and Agrobacterium tumefaciens. The lipids extracted at a laboratory and pilot scale from the biomasses were enriched in arachidonic acid, astaxanthin, and co-enzyme Q10 respectively. Extractions were also performed on marine microalgae, produced by a proprietary fermentation process, to obtain lipids rich in EPA. Lipids were extracted from wet biomass using DME, which removes the need to dry the biomass. Water is also co-extracted, which has to be separated from the lipid. The biomass shrunk considerably during packed bed extraction of wet biomass, leading to channelling. Repacking and re-extraction of the packed bed enabled full lipid yields to be obtained. The extraction of lipids from biomass suspended in fermentation broth showed considerable promise, and lipid yields were improved due to the recovery of lipids that had been exuded into the broth from the microorganism. In contrast, the extraction of lipids from freeze-dried biomass using DME was routine, yields were substantially higher than using CO₂ or CO₂ + ethanol, but were lower than from wet biomass. DME also extracted polar lipids from both wet and dry biomass, leading to the higher total lipid yields compared to CO₂. Separate extraction of non-polar and polar lipids was possible by sequential extraction of dry biomass using initially CO₂ followed optionally with ethanol co-solvent; and then DME.     

Suitability of Soxhlet Extraction to Quantify Microalgal Fatty Acids as Determined by Comparison with In Situ Transesterification

To assess Soxhlet extraction as a method for quantifying fatty acids (FA) of microalgae, crude lipid, FA content from Soxhlet extracts and FA content from in situ transesterification (ISTE) were compared. In most cases, gravimetric lipid content was considerably greater (up to sevenfold) than the FA content of the crude lipid extract. FA content from Soxhlet lipid extraction and ISTE were similar in 12/18 samples, whereas in 6/18 samples, total FA content from Soxhlet extraction was less than the ISTE procedure. Re-extraction of residual biomass from Soxhlet extraction with ISTE liberated a quantity of FA equivalent to this discrepancy. Employing acid hydrolysis before Soxhlet extraction yielded FA content roughly equivalent to ISTE, indicating that acidic conditions of ISTE are responsible for this observed greater recovery of FA. While crude lipid derived from Soxhlet extraction was not a useful proxy for FA content for the species tested, it is effective in most strains at extracting total saponifiable lipid. Lipid class analysis showed the source of FA was primarily polar lipids in most samples (12/18 lipid extracts contained <5% TAG), even in cases where total FA content was high (>15%). This investigation confirms the usefulness of ISTE, reveals limitations of gravimetric methods for projecting biodiesel potential of microalgae, and reinforces the need for intelligent screening using both FA and lipid class analysis.     

Efficient Extraction of Astaxanthin from Phaffia rhodozyma with Polar and Non-polar Solvents after Acid Washing

method of extracting astaxanthin from Phaffia rhodozyma with various solvents after acid washing was investigated. The extraction efficiency was distinctly increased after acid washing of P. rhodozyma cells. When the concentration of HCl was 0.4 mol·L^-1, the highest extraction efficiency of astaxanthin was achieved which was about three times higher than the control. Acetone or benzene as single polar or non-polar solvent was the most effective solvent in our research. With a combination of isopropanol and n-hexane (volume ratio of 2:1), the maximal extraction efficiency was achieved, approximately 60% higher than that obtained with a single solvent. The liquid-solid ratio and the extracting time were also optimized. Under the optimum extraction conditions, the extraction yield of astaxanthin exceeded 98%.     

采用极性及非极性溶剂从酸洗后的红法夫酵母中高效萃提虾青素的研究(英文)

method of extracting astaxanthin from Phaffia rhodozyma with various solvents after acid washing was investigated.The extraction efficiency was distinctly increased after acid washing of P.rhodozyma cells.When the concentration of HCl was 0.4 mol·L-1,the highest extraction efficiency of astaxanthin was achieved which was about three times higher than the control.Acetone or benzene as single polar or non-polar solvent was the most effective solvent in our research.With a combination of isopropanol and n-hexane(volume ratio of 2:1),the maximal extraction efficiency was achieved,approximately 60% higher than that obtained with a single solvent.The liquid-solid ratio and the extracting time were also optimized.Under the optimum extraction conditions,the extraction yield of astaxanthin exceeded 98%.