微藻的高油脂化技术

温室效应与石化能源紧缺已成为全球问题,生物燃料作为一种可再生且环境友好的替代能源受到人们的普遍关注。不少微藻油含量高,环境适应性强,净碳值几乎为零,被认为是生物质能,尤其生物柴油最重要的原料来源之一。本文综述了油脂微藻的国内外研究现状,并对高油脂微藻藻种筛选、高密度培养,以及提高微藻油脂含量和产油速率的可能方法进行了讨论;阐述了采用基因工程技术调控微藻脂类代谢途径生产高油脂的可能性;最后介绍了以CO2废气为碳源,膜生物反应器强化微藻培养技术,为进一步降低微藻产油成本,提高微藻生物柴油经济性提出了一条极有可能实现工业化的潜在高效生产途径。     

甲酸处理对微藻油脂提取的影响

采用易于回收的有机酸处理微藻细胞,以微藻Chlorella protothecoides为原料,系统研究了甲酸处理对微藻油脂提取的影响.结果表明,甲酸能有效破碎微藻细胞,最终油脂得率和脂肪酸甲酯(FAME)得率均与传统无机酸热法相当.甲酸浓度、温度和处理时间对油脂提取有显著影响.当甲酸浓度为88%,液固比为6 m L/g,100℃下处理30 min,Chlorella protothecoides油脂得率为49.2%,FAME得率高达92.1%.甲酸处理提取到的微藻油脂脂肪酸组成与无机酸热法结果无明显区别.Chlorella protothecoides油脂主要含有5种脂肪酸,其中C18∶1含量最高.实验还考察了甲酸处理对Nannochlorum sp和Nannochloropsis oceanic的适用性,结果表明,对于不同微藻原料,甲酸处理提取到的微藻油脂得率和FAME得率均与无机酸热法结果相当.     

能源微藻采收及油脂提取技术

微藻具有光合效率高、生长周期短、油含量高等特性,是一种极具前景的生物柴油大宗原料。藻体采收和油脂提取是决定微藻柴油生产成本的关键环节,此下游技术的改进对提高微藻产油的经济性意义重大。本文综述了国内外微藻培养液的浓缩采收方法,并对絮凝沉降、絮凝气浮、离心和过滤等方法的作用机制和采收效率进行比较;阐述了目前微藻油脂的提取技术,从操作条件和能量消耗角度分别对有机溶剂、超临界和亚临界法进行评价;特别介绍了一种同时实现微藻生长和油脂提取的新型微藻油脂原位萃取法;最后总结了微藻能源下游技术中存在的主要问题和今后的发展方向,为进一步提高微藻生物柴油经济性提出参考性意见。     

影响微藻规模化培养的因素

概述了微藻生物能源技术中的微藻规模化培养的研究现状,从藻种筛选、代谢机理、培养条件和光生物反应器几个不同的角度阐述了影响微藻规模化培养的因素,为微藻生物能源的发展及光生物反应器的研发提供建议与思路.     

高酸值生物柴油原料甘油酯化脱酸研究

利用共沉淀-浸渍法制备了Al改性固体酸催化剂SO₄^2-/ZrO₂,考察了催化剂在甘油酯化脱酸制备生物柴油原料反应中的催化活性、重复利用性和再生性能,并对使用前后的催化剂进行了红外光谱分析。研究表明,添加适量Al(1%,以Al₂O₃的质量分数计)不但提高了催化剂的活性,还改善了催化剂的重复利用性和再生性能。添加Al使ZrO₂上SO₄^2-的量增加,SO₄^2-结合强度增强,减少了在酯化脱酸反应过程中SO₄^2-的流失。在SO₄^2-/ZrO₂-Al₂O₃催化剂用量为7％、甘油与酸物质的量比为6:1、反应温度为140 ℃、反应时间为4 h的条件下,酯化率可达91%以上,可将高酸值油脂的酸值从31 mg_KOH/g降低到2.8 mg_KOH/g以下,可满足生物柴油原料的要求。     

废弃油脂生产生物柴油的研究进展

简单介绍了生物柴油的生产原料,综述了用废弃油脂生产生物柴油的现状和方法。废弃油脂生产生物柴油的方法主要有物理法和化学法,物理法主要有掺和法和微乳法,化学法主要有热裂解法和酯交换法。目前生产中采用化学法的酯交换法、以酸碱两步催化法的工艺为主,而生物酶法和超临界法是研究热点。     

生物油脂新型环氧化过程及机理研究

以金属有机化合物甲基三氧化铼(MTO)为催化剂, 双氧水为氧化剂新型化学方法合成环氧大豆油. 详细考察了催化剂在双氧水、溶剂和助剂等因素下的催化性能. 研究了该催化体系在其他油脂环氧化中的应用, 环氧产物的选择性在99%以上. 采用红外光谱法(IR)对产品进行表征. 通过紫外-可见分光光度法(UV-Vis)对催化剂的研究, 发现催化剂(MTO)在催化环氧化过程中形成催化中间体, 且催化活性很高. 对催化剂和双氧水相互作用机理及新型环氧化反应的机理进行了初步研究.     

生物基甘油高值化研究进展

生物柴油的生产过程中会产生大量的生物基甘油,随着生物柴油的大规模发展,生物基甘油正不断地被发现新的商业应用价值。结合近期国内外相关研究论文,归纳分析了生物基甘油的高值化研究进展,并展望了生物基甘油在化学工业中的发展。     

气相色谱法在生物柴油生产工艺研究中的应用

综述了气相色谱法在生物柴油生产工艺研究中的应用,包括反应产物和生物柴油产品中脂肪酸甲酯含量和分布的测定,单脂肪酸甘油酯、二脂肪酸甘油酯和三脂肪酸甘油酯含量的测定,游离脂肪酸含量的测定以及微量甲醇含量的测定等。讨论了进样方式、色谱柱类型、硅烷化等因素对反应产物组成测定的影响;提出了一种采用双柱压力反吹的方式测定生物柴油产品中微量甲醇含量的方法：采用正丙醇作内标,甲醇与内标通过预切柱进入分析柱后,通过压力变化,将其余组分通过分流出口反吹出色谱系统;采用极性聚乙二醇色谱柱测定了8种不同植物油中脂肪酸甲酯的含量和分布。     

柴油溶剂中脂肪酶催化高酸值废油脂酯化制备生物柴油

采用0＃柴油作为反应溶剂,利用固定化脂肪酶催化高酸值废油脂与甲醇酯化反应制备生物柴油。来源于Candida antarctica的固定化脂肪酶Novozym435在0＃柴油溶剂中具有极高的催化活性。以酸价高达157×10-3的废油脂为原料,废油脂质量比10%的Novozym435,甲醇与废油脂初始摩尔比2∶1,0＃柴油与废油脂质量比5∶1,摇床摇速170r/min,50℃下反应2h甲酯化率可达95.10%。0＃柴油作为反应溶剂有效地溶解了高酸值废油脂和甲醇,降低了反应体系的黏度和消除了甲醇对Novozym435的负面影响,提高了Novozym435的稳定性。同时,0＃柴油溶剂对未脱胶废油脂中残留的对脂肪酶有害的磷脂等胶类物质具有一定的稀释作用。该工艺省却了溶剂蒸馏的繁琐工序,直接得到脂肪酸甲酯和石化柴油的混合燃料。     

微藻脂肪合成与代谢调控

随着能源与环境问题的日益严峻,利用微藻生产生物柴油已经成为研究者们关注的焦点。与传统油料作物相比,微藻具有生长速度快、含油量高、不占用耕地等优势,是极具潜力的生物燃料生产原料。虽然许多微藻在压力条件下会在细胞内积累脂肪,特别是中性脂肪三酰甘油(TAG),它是生产生物柴油的主要原料,但目前对于微藻脂肪的合成和代谢调控还了解的很少。为了更好地理解和操纵微藻脂肪代谢以增强脂肪积累,本文综述了微藻脂肪合成与代谢调控的研究进展,包括TAG生物合成途径,提高脂肪积累的生化调控和基因工程策略,阐述了营养控制对脂肪积累的影响,总结了增强脂肪酸合成途径、增强Kennedy途径、调控TAG旁路途经、抑制脂肪合成的竞争途径、抑制脂肪的分解代谢等5种基因工程策略,同时也对微藻脂肪代谢研究的发展进行了展望。     

Highly Valuable Polyunsaturated Fatty Acids from Microalgae: Strategies to Improve Their Yields and Their Potential Exploitation in Aquaculture

Microalgae have a great potential for the production of healthy food and feed supplements. Their ability to convert carbon into high-value compounds and to be cultured in large scale without interfering with crop cultivation makes these photosynthetic microorganisms promising for the sustainable production of lipids. In particular, microalgae represent an alternative source of polyunsaturated fatty acids (PUFAs), whose consumption is related to various health benefits for humans and animals. In recent years, several strategies to improve PUFAs’ production in microalgae have been investigated. Such strategies include selecting the best performing species and strains and the optimization of culturing conditions, with special emphasis on the different cultivation systems and the effect of different abiotic factors on PUFAs’ accumulation in microalgae. Moreover, developments and results obtained through the most modern genetic and metabolic engineering techniques are described, focusing on the strategies that lead to an increased lipid production or an altered PUFAs’ profile. Additionally, we provide an overview of biotechnological applications of PUFAs derived from microalgae as safe and sustainable organisms, such as aquafeed and food ingredients, and of the main techniques (and their related issues) for PUFAs’ extraction and purification from microalgal biomass.     

Overcoming the Biological Contamination in Microalgae and Cyanobacteria Mass Cultivations for Photosynthetic Biofuel Production

Microalgae and cyanobacteria have shown significant potential for the development of the next biofuels innovation because of their own characteristics as photosynthetic microorganisms. However, it is confronted with a lot of severe challenges on the economic scaling-up of the microalgae- and cyanobacteria-based biofuels production. One of these major challenges is the lack of a reliable preventing and controlling culture system of biological contamination, which can attack the cell growth or product accumulation causing crashing effects. To increase the commercial viability of microalgae- and cyanobacteria-based biofuels production, overcoming the biological contaminations should be at the top of the priority list. Here, we highlight the importance of two categories of biological contaminations and their controlling strategies in the mass cultivations of microalgae and cyanobacteria, and outline the directions that should be exploited in the future.     

Production,Purification, and Study of the Amino Acid Composition of Microalgae Proteins

Microalgae are known to be rich in protein. In this study, we aim to investigate methods of producing and purifying proteins of 98 microalgae including Chlorella vulgaris, Arthrospira platensis, Nostoc sp., Dunaliella salina, and Pleurochrysis carterae (Baltic Sea). Therefore, we studied their amino acid composition and developed a two-stage protein concentrate purification method from the microalgae biomass. After an additional stage of purification, the mass fraction of protein substances with a molecular weight greater than 50 kDa in the protein concentrate isolated from the biomass of the microalga Dunaliella salina increased by 2.58 times as compared with the mass fraction before filtration. In the protein concentrate isolated from the biomass of the microalga Pleurochrysis cartera, the relative content of the fraction with a molecular weight greater than 50.0 kDa reached 82.4%, which was 2.43 times higher than the relative content of the same fractions in the protein concentrate isolated from this culture before the two-stage purification. The possibilities of large-scale industrial production of microalgae biomass and an expanded range of uses determine the need to search for highly productive protein strains of microalgae and to optimize the conditions for isolating amino acids from them.     

基因工程中的液相色谱

 对液相色谱用于基因工程生产蛋白质分子构象、变性蛋白的复性、蛋白折叠中间体等方面的研究进展,以及液相色谱在基因工程样品的质量 检验、制备方面的新进展分别加以评述。全文引用了42篇文献。     

Engineering of Streptoalloteichus tenebrarius 2444 for Sustainable Production of Tobramycin

Tobramycin is a broad-spectrum aminoglycoside antibiotic agent. The compound is obtained from the base-catalyzed hydrolysis of carbamoyltobramycin (CTB), which is naturally produced by the actinomycete Streptoalloteichus tenebrarius. However, the strain uses the same precursors to synthesize several structurally related aminoglycosides. Consequently, the production yields of tobramycin are low, and the compound’s purification is very challenging, costly, and time-consuming. In this study, the production of the main undesired product, apramycin, in the industrial isolate Streptoalloteichus tenebrarius 2444 was decreased by applying the fermentation media M10 and M11, which contained high concentrations of starch and dextrin. Furthermore, the strain was genetically engineered by the inactivation of the aprK gene (∆aprK), resulting in the abolishment of apramycin biosynthesis. In the next step of strain development, an additional copy of the tobramycin biosynthetic gene cluster (BGC) was introduced into the ∆aprK mutant. Fermentation by the engineered strain (∆aprK_1-17L) in M11 medium resulted in a 3- to 4-fold higher production than fermentation by the precursor strain (∆aprK). The phenotypic stability of the mutant without selection pressure was validated. The use of the engineered S. tenebrarius 2444 facilitates a step-saving, efficient, and, thus, more sustainable production of the valuable compound tobramycin on an industrial scale.     

遗传算法及其在化学化工中的应用

本文介绍了遗传算法的基本概念、工作原理和步骤, 综述了它在化学化工领域的应用。     

Mass cultivation of various algal species and their evaluation as a potential candidate for lipid production

Microalgae have been proposed as a promising source for biodiesel production. Focusing on algal strains for biodiesel production, efforts should be made to search new strains. Experiments were carried out to investigate the effects of growth parameters (nutrients, pH, light, aeration and temperature) and the oil percentage of eight algal strains (Chlorella sp., Cladophora sp., Hydrodictylium sp., Oedogonium sp., Oscillatoria sp., Spirogyra sp., Stigeocolonium sp., Ulothrix sp.). Results show that 6.5–7.5 is the optimum pH for the growth of all algal species. Temperature showed a greater variation (25°40°C). Ulothrix sp. gave more biomass productivity and is the most suitable strain for biodiesel production due to higher oil percentage (62%). Least biomass production was observed for Stigeocolonium sp. and least oil content was obtained from Hydrodictylium sp. It was observed that among these eight algal strains for biodiesel production, Ulothrix and Chlorella are the most promising algae species.