MICROALGAE AS A SOURCE OF FATTY ACIDS

Microalgae are a very diverse group of organisms that consist of both prokaryotic and eukaryotic forms. Although most microalgae are phototrophic, some species are also capable of heterotrophic growth. Some species of microalgae can be induced to overproduce particular fatty acids through simple manipulations of the physical and chemical properties of the culture medium. As a result of the profound differences in cellular organization and growth modes and the ability to manipulate their fatty acid content, microalgae represent a significant source of unusual and valuable lipids and fatty acids.
The utilization of microalgal lipids and fatty acids as food components requires that these organisms be grown at large scale under controlled conditions. Several growth systems have been developed for large scale growth of phototrophic microalgae using either natural sunlight or artificial light, but their lack of control of culturing parameters or their high cost of operation have limited their utility for the production of food products. Instead, large scale cultivation of heterotrophic microalgae using classical fermentation systems provides consistent biomass produced under highly controlled conditions at low cost.
Microalgae contain many of the major lipid classes and fatty acids found in other organisms. However, they are also the principal producers in the biosphere of some polyunsaturated fatty acids, especially docosahexaenoic acid (DHA). The high DHA content found in some algae is currently being utilized to supplement infant formula to enable it to more closely resemble human breast milk. Thus, the commercialization of DHA from microalgae demonstrates the value of these organisms as a source of useful fatty acids.     

微藻脂类组成及脂肪酸分布的分析技术

微藻具有光合效率高、生长周期短、有可能异养生长等特性, 并含有多种生物活性物质,尤其是 EPA、DHA 等多不饱和脂肪酸含量丰富, 可以作为功能食品的优质生物资源。多不饱和脂肪酸在微藻细胞中主要以脂质的形式存在, 脂类组成及脂肪酸分布信息可以为藻种筛选、不饱和脂肪酸的分离纯化等提供依据。本文综述了高产多不饱和脂肪酸的藻种, 脂质及脂肪酸的萃取方法与分离鉴定技术, 特别对全二维气相色谱法、高压液相色谱法在微藻中的应用进行了阐述。     

破壁方式对微藻油脂提取物中脂肪酸的影响

本实验研究了超声波处理、挤压膨化、反复冻融、高压均质四种破壁方式对微藻油脂提取率及油脂中脂肪酸的影响,探寻最佳破壁方法.研究表明:采用混合溶剂正己烷∶乙醇=10∶3提取微藻油脂,超声辅助破壁、高压均质破壁、挤压膨化破壁、反复冻融破壁后提油的油脂得率分别26.19％±0.25％、22.46％±0.17％、25.56％±0...     

Commercial applications of microalgae

The first use of microalgae by humans dates back 2000 years to the Chinese, who used Nostoc to survive during famine. However, microalgal biotechnology only really began to develop in the middle of the last century. Nowadays, there are numerous commercial applications of microalgae. For example, (i) microalgae can be used to enhance the nutritional value of food and animal feed owing to their chemical composition, (ii) they play a crucial role in aquaculture and (iii) they can be incorporated into cosmetics. Moreover, they are cultivated as a source of highly valuable molecules. For example, polyunsaturated fatty acid oils are added to infant formulas and nutritional supplements and pigments are important as natural dyes. Stable isotope biochemicals help in structural determination and metabolic studies. Future research should focus on the improvement of production systems and the genetic modification of strains. Microalgal products would in that way become even more diversified and economically competitive.     

微藻生物活性物质在食品工业中的应用进展

微藻能产多种生物活性物质,其中一些可以作为功能性食品的添加剂。一些微藻能积累大量人体所需的超长链不饱和脂肪酸,包括花生四烯酸(ARA)、二十碳五烯酸(EPA)和二十二碳六烯酸(DHA)。尽管利用微藻生产DHA技术已得到商业化应用,其他超长链不饱和脂肪酸仍尚不能通过微藻商业化生产。微藻中的多糖是微藻的细胞结构成分、储能物质或充当其他生理功能,它们通常具有粘弹性等流变特性,因此它们不仅可以作为保健食品的功能因子,还适合作果冻和饮料的配料。类胡萝卜素、藻胆蛋白和叶绿素等色素,具有生物活性,可作为具有保健作用的食品着色剂。一些微藻类胡萝卜素已经能够商业化生产,但是像叶绿素等其他微藻色素的工业化生产技术仍待开发。微藻还能合成多种具有抗病毒、抗氧化和血管紧张素转换酶抑制活性的肽,一些生物活性肽也可通过水解微藻蛋白获得。本文综述了微藻的生物活性物质以及这些活性成分在功能性食品中应用的可能性。     

Extremophile microalgae as feedstock for high-value carotenoids: A review

There are places in our planet where environmental conditions are beyond normal limits for growth but still harbour life. Extremophile microalgae are the candidates for large-scale production because (i) their extreme growth conditions help to avoid unwanted contaminations, facilitating their production and (ii) in order to survive under harsh environments, these microorganisms synthesise valuable uncommon biomolecules. Extremophile microalgae include Arthrospira platensis, used as a source of phycocyanin and produced under highly alkaline conditions, and Dunaliella salina, which is industrially produced as a source of β-carotene and can naturally resist salinity conditions exceeding 300 g L⁻¹. Microalgae can be produced on non-arable lands, using seawater, and within a wide range of environmental conditions, allowing their production in almost any part of the planet. The current paper aimed at highlighting the biotechnological potential of extremophile microalgae as sources for carotenoids, valuable molecules used as pigments and health-promoters.     

Green ultra-high pressure extraction of bioactive compounds from Haematococcus pluvialis and Porphyridium cruentum microalgae

Microalgae are considered prolific sources of bioactive compounds that can be useful for nutraceuticals. In this study, the potential of ultra-high pressure extraction (UHPE) for the simultaneous cell disruption and extraction of bioactives from two microalgae species, Haematococcus pluvialis and Porphyridium cruentum, was evaluated. The variables studied to extract carotenoids for H. pluvialis were pressure (100–600 MPa) and number of cycles (1 and 3 cycles) whereas the variables studied to obtain bioactives such as B-phycoerythrin, carotenoids, and PUFAs for P. cruentum were pressure (100–600 MPa) and different extraction solvents (water, ethanol, ethyl acetate or ethanol/d-limonene), generally recognized as safe (GRAS). The UHPE results showed significant increase on the extraction of carotenoids (109.74–119.34 mg per g extract) from H. pluvialis using 1 cycle of 20 min regardless of the pressure used. For P. cruentum, an UHPE with water provided extracts enriched in B-phycoerythrin (up to 144.43 mg per g extract), while subsequent UHPE using ethanol, ethyl acetate or ethanol/d-limonene 1:1 (v/v) provided extracts enriched in carotenoids (up to 65.05 mg per g extract) and polyunsaturated fatty acids (mainly eicosapentanoic acid and linoleic acid). Therefore, UHPE proved to be a viable green alternative for the recovery of bioactives from microalgae biomass.Industrial relevance: Microalgae are promising sources of bioactives such as B-phycoerythrin, carotenoids and polyunsaturated fatty acids. The potential of ultra-high-pressure extraction (UHPE) has been demonstrated as a fast and viable eco-friendly alternative using GRAS solvents (water, ethanol, ethyl acetate or ethanol/d-limonene) for the simultaneous cell disruption and extraction of these bioactives from Haematococcus pluvialis and Porphyridium cruentum. The bioactives obtained with one step or two step-UHPE process can be used in an array of food, cosmetic and pharmaceutical applications.     

PCR amplification of 18S rRNA,single cell protein production and fatty acid evaluation of some naturally isolated microalgae

Microalgae were isolated during a screening program from soil samples collected from paddy-fields of Fars province, south of Iran. The protein content was assayed by the Kochert method. Total genomic DNA were isolated and used for PCR amplification of the 18S rRNA gene. The sequences were determined for 12 species of microalgae. Some bioinformatic tools were used for more investigation on these biologic data. Total lipids from five microalgal species were extracted and used for determination of different types of fatty acids by gas chromatography–mass spectrometry method. In our experiments the green algae yielded a maximum protein of about 42% ± 1.64. The DNA sequences were published in the NCBI under specific accession numbers. The composition of fatty acids was mainly, myristic acid, palmitic acid, oleic acid, α-linolenic acid, and γ-linolenic acid.     

Differential scanning calorimetry evaluation of oxidation stability of docosahexaenoic acid in microalgae cells and their extracts

The aim of this work was to evaluate the oxidative stability of docosahexaenoic acid (DHA) from Aurantiochytrium limacinum SR21 microalgae cells and in their lipidic extract by differential scanning calorimetry (DSC). Besides, freezing was evaluated as a strategy for microalgal DHA long‐term conservation by analysing changes in their thermal properties. As a first approach, mixtures of the most representative A. limacinum SR21‐fatty acids were evaluated in model systems. DHA and palmitic acid were the major polyunsaturated and saturated fatty acids produced by the microalgae cells, respectively. Changes in DHA/palmitic acid ratio in model systems, in cells and their lipidic extracts, were detected by DSC through shifts in the oxidation onset temperature (OOT) values. However, OOT values of cells and lipidic extracts could be also influenced by cellular compartmentalisation, carotenoids and other components presence. Freezing was not a good strategy for DHA long‐term conservation, as revealed by OOT values and thermal properties, which reflected the extensive changes that occurred during storage.     

The Evolution and Versatility of Microalgal Biotechnology: A Review

Microalgal biotechnology has emerged due to the health‐promoting properties of microalgae related to their bioactive compounds and the great diversity of products that can be developed from algal biomass. Microalgal biomasses have been produced industrially for applications in different fields such as food, pharmaceutical, nutraceutical, cosmetic, and animal feed industries. They can be cultivated either in open systems or in closed systems (photobioreactors). Another important area is the use of microalgal biomass for energy production. It has become obvious that petroleum‐derived fuels are unsustainable, due to depleting world reserves and greenhouse gas emissions. Microalgae can provide several different types of renewable biofuels. These include methane produced by anaerobic digestion of the algal biomass, biodiesel derived from trans‐esterification of microalgal lipids, bioethanol produced from carbohydrate fermentations, and photobiologically produced biohydrogen. The idea of using microalgae as a source of fuel is not new. However, it is now being taken seriously because of increases in petroleum prices and, more significantly, the increasing concern about global warming as associated with burning fossil fuels. This review offers an update on information about microalgae, specifically emphasizing their biotechnological importance.     

微藻油脂合成的转录调控研究进展

生物燃料是传统化石燃料的理想替代品,微藻是生产生物燃料的优良原料,通过对微藻油脂合成和调控的了解,能够有效提高微藻生产生物柴油的效率。转录因子是一种具有特殊功能结构、行使调控基因表达功能的蛋白质分子,在复杂的油脂合成代谢过程中,转录因子能对代谢过程中多个酶系进行集体调控,从而促进藻细胞中油脂积累。从微藻油脂的合成途径出发,简要介绍了合成途径中的关键酶,重点综述了bZIP、MYB、Dof、bHLH转录因子对于微藻油脂合成的调控影响。微藻油脂合成涉及多个亚细胞单位的多条途径,是一个十分复杂的代谢网络过程,通过基因工程手段改变合成途径中相关酶的表达可以增加微藻中油脂积累。     

微藻类胡萝卜素生物合成代谢途径的研究进展

微藻是一类没有根茎叶,却能够进行光合作用的真核生物。由于微藻生长速度快、适应性强、生长不受季节影响,因此选择微藻作为提取类胡萝卜的主要原料越来越受到人们的青睐。微藻含有多种多样的生物活性化合物,如:色素、多糖和长链多不饱和脂肪酸等,它们在食品、药品及其他行业中被广泛应用。其色素包括类胡萝卜素、藻胆蛋白等,且富含的类胡萝卜素主要包括番茄红素、叶黄素和虾青素等。类胡萝卜素对视觉系统、皮肤组织有保健功能,并且能够抵抗强光、高温或深水等不良环境。本文在归纳总结主要类胡萝卜素的种类及类胡萝卜素在微藻中的分布及特点的基础上,重点对微藻中类胡萝卜素生物合成代谢途径和其过程中的相关基因以及基因克隆现状进行了阐述,为微藻类胡萝卜素代谢途径的深化研究提供参考。     

7种富油微藻的超临界提取及脂肪酸分布特征

富油微藻是制备生物燃料和提取高附加值不饱和脂肪酸的理想原料。为筛选具有高产油潜能的微藻,开发经济高效的微藻油脂提取工艺和检测方法,本文对7种富油微藻进行超临界CO2提取,并结合三氟化硼-甲醇衍生化、GC-MS分析了各微藻提取物中的35种脂肪酸组成和含量。结果表明,添加乙醇夹带剂后,各藻类的油脂收率由54.60 % ~ 82.16 %提高至75.61 % ~ 104.46 %。微藻中共检出18种脂肪酸,C16 ~ C18系列脂肪酸含量均在55.97 %以上,其中小球藻、三角褐指藻和青岛大扁藻的单不饱和脂肪酸含量分别为36.25 %、31.81 %和26.85 %,是生物柴油理想的替代品。牟氏角毛藻的不饱和脂肪酸UFAs含量达到91.15 %,可作为绿色医疗保健品的重要来源。     

Industrial potential of carotenoid pigments from microalgae: Current trends and future prospects

Microalgae are rich source of various bioactive molecules such as carotenoids, lipids, fatty acids, hydrocarbons, proteins, carbohydrates, amino acids, etc. and in recent Years carotenoids from algae gained commercial recognition in the global market for food and cosmeceutical applications. However, the production of carotenoids from algae is not yet fully cost effective to compete with synthetic ones. In this context the present review examines the technologies/methods in relation to mass production of algae, cell harvesting for extraction of carotenoids, optimizing extraction methods etc. Research studies from different microalgal species such as Spirulina platensis, Haematococcus pluvialis, Dunaliella salina, Chlorella sps., Nannochloropsis sps., Scenedesmus sps., Chlorococcum sps., Botryococcus braunii and Diatoms in relation to carotenoid content, chemical structure, extraction and processing of carotenoids are discussed. Further these carotenoid pigments, are useful in various health applications and their use in food, feed, nutraceutical, pharmaceutical and cosmeceutical industries was briefly touched upon. The commercial value of algal carotenoids has also been discussed in this review. Possible recommendations for future research studies are proposed.     

通过商品化DHA藻油的脂肪酸组成推测其微藻属名

DHA是一种重要的功能性ω-3多不饱和脂肪酸.我国卫生部相继批准了寇氏隐甲藻、裂壶藻、吾肯氏壶藻DHA藻油为新资源食品.收集并分析了9个商品化DHA藻油的脂肪酸含量,结合文献数据,发现通过商品化DHA藻油的脂肪酸特征推测其微藻属名是可行的.其中寇氏隐甲藻DHA藻油中长链多不饱和脂肪酸只含DHA,几乎不合DPA.裂壶藻与吾肯氏藻DHA藻油中长链多不饱脂肪酸主要以DHA和DPA为主,DHA/DPA比例随藻种而恒定,几乎不随发酵条件而有明显变化;DHA/DPA比例在2～3的DHA藻油多半来自裂壶藻;DHA/DPA比例在4～6的DHA藻油既可能来自裂壶藻也可能来自吾肯氏壶藻.     

Cultivation and downstream processing of microalgae and cyanobacteria to generate protein-based technofunctional food ingredients

Abstract

Microalgae are unicellular microorganisms that can be rich in proteins and are therefore a valuable ingredient in different foods. So far microalgae are mainly utilized in foods in low concentrations as a whole-cell ingredient even though it is known that proteins extracted from microalgae can possibly posess various technofunctional properties, such as high protein solubility, emulsification, foaming, and gelation properties. The widespread usage of protein-rich ingredients obtained from microalgae is for the most part prevented by the high price of the biomass, the lack of efficient downstream processes, and the adverse taste. The aim of this review is to give insights into the fundamental properties of the growth and processing of microalgae, highlight the advantages of microalgae ingredients and show potential applications based on the technofunctional, nutritional and sensory properties that were reported. Moreover, the existing challenges and knowledge gaps that hinder the application of microalgal proteins in foods are discussed.     

基于微藻的废水处理及油脂积累研究进展

水资源危机和对环境污染的担忧推动了传统废水处理工艺的升级。微藻可大量积累油脂等高附加值次级代谢产物,而微藻在废水中培养,可同时满足获取微藻生物质和废水处理的需求。综述了微藻培养与废水处理相结合的特点,阐述了微藻废水处理工艺,包括光生物反应器、生物膜-光生物反应器、微藻-细菌共培养、微藻型微生物燃料电池以及耦合植物生长调节剂,对提高废水中微藻生物活性、产油能力和废水处理效率的作用。鉴于废水组成的复杂性和微藻的适应性,还需创新废水微藻培养工艺与技术以实现更高的废水生物修复效率和微藻高附加值产物产率。     

大豆蛋白/壳聚糖凝聚法制备微藻油乳液及其稳定性研究

微藻油富含ω-3多不饱和脂肪酸二十二碳六烯酸(DHA)与二十碳五烯酸(EPA),在液体食品中的应用日趋广泛。但是微藻油极易在食品加工、保藏和消化过程中发生氧化劣变;同时脂溶性的微藻油难以添加至液体食品中。因此,改善和提高微藻油的稳定性是其应用到食品中的关键问题。本文利用大豆分离蛋白(SPI)/壳聚糖(CS)复合凝聚物(Coacervate)制备了微藻油乳液。由于乳液的氧化稳定性很大程度上依赖于其物理稳定性,本文系统研究了微生物谷氨酰胺转氨酶(m TGase)交联对微藻油乳液物理稳定性及氧化稳定性的影响。实验结果表明,在p H为6.0,CS/SPI比例为0.1 g/g,m TGase浓度为25 U/g SPI的条件下,m TGase对SPI/CS凝聚物的交联效果最好。m TGase交联明显改善了微藻油乳液的物理稳定性及氧化稳定性,并显著提高了微藻油的乳化效率。通过此方法制备的微藻油乳液产品可应用于豆奶等液体蛋白饮料从而达到强化DHA的目的。