微藻生物柴油技术的研究现状及展望

微藻生物柴油是一种优良的可再生新能源,对于解决人类面临的能源短缺和全球变暖两大危机具有潜在的重大战略意义。综述了微藻生物柴油的技术流程、油脂含量较高的微藻藻种、微藻生物柴油的最大技术瓶颈、提高微藻油脂总产量的方法、微藻的大规模培养、微藻的采收和微藻生物柴油的制取等方面的研究现状,并对微藻生物柴油未来的核心研究方向提出了初步见解。     

抗生素在微藻工程中的应用研究进展

微藻具有极高的应用价值,近些年来针对于微藻的研究也越来越受到重视。抗生素的使用是微藻进行无菌化及突变体筛选等微藻研究中常用的手段之一,抗生素的作用会对微藻的生长代谢、生理活性等产生影响。现将近年来抗生素在微藻工程中的应用研究进行综述,包括抗生素在微藻无菌化培养及微藻突变株筛选中的应用及抗生素对微藻生长和生理上的影响,并对今后抗生素在微藻工程中的研究前景进行展望。     

微藻废水生物处理技术研究进展

微藻因生长速率快、细胞脂质含量高及具有生物隔离二氧化碳能力,已作为新一代生物质能源受到广泛关注.然而,投入大量淡水资源并需在生长期间持续提供营养物质已成为规模化培育微藻的主要障碍.将微藻培育系统与废水处理相结合是经济可行的污水资源化方案.基于微藻生长期间对氮磷等营养物质的利用机制,本文综述了微藻在各类废水生物处理过程中的应用情况,着重分析了其对废水中有机与无机化合物、重金属以及病原体的去除或抑制能力.同时,考察了废水初始营养物浓度、光照、温度、pH与盐度以及气体交换量等环境因素对微藻生长代谢的影响.此外,结合微藻规模化应用所面临的问题,对微藻废水处理技术的应用前景及发展方向进行了展望,旨在为水生态系统的建设与管理提供参考.     

微藻规模化培养研究进展

微藻作为地球上最古老的物种之一,其诞生可追溯到35亿多年前.微藻的种类十分丰富,形态也多种多样.微藻一般都含有叶绿体,因此可进行光合作用,有研究表明微藻固定CO2的能力是陆地植物的10倍.微藻以其丰富的代谢产物及独特的生理特性在可再生能源、生物医药、食品工业和环境监测等方面有着广泛的应用.然而如何在控制成本的前提下对微...     

植物单细胞蛋白资源——小球藻开发利用研究的现状

微藻大规模培养的应用研究已越来越受到重视,发展成为生物技术领域的一门新的领域──微藻生物技术Micro-algalBiotechnology．小球藻是微藻中首先被开发利用的种类之一,其培养方式已由开放池培养发展为利用生物反应器进行连续培养。本文就小球藻的培养技术、主要化学成分和作为食品、饲料,以及在工业上的应用研究的现状进行简要评述,并展望了小球藻开发利用的前景。     

微藻生物燃料及高价值产物的代谢研究进展

微藻是当今代谢工程领域最具潜力的燃料生物质来源之一.其结构简单、基因可操作性强的特点使其可通过不同的代谢工程手段得到丰富多样的生物燃料和高价值产物.本文系统地总结了近年来国内外利用微藻在脂质、氢气、乙烯、醇类、脂肪醇和脂肪烃、糖类、萜类及其他高价值产物的生产中取得的进展,并通过介绍着眼于改变光合作用关键酶体或复合物以提升生物质产量的相关研究进展,分析了生物质合成代谢途径的改变对上游光合作用的潜在影响.结合系统生物学及生物信息学方法筛选高效的微藻株系,改变碳流方向以提升生物质的合成效率,实现高效地同源重组,提高外源基因在微藻内的表达效率是微藻代谢工程亟待解决的问题.本文在此基础上结合近年来各个交叉学科的发展趋势,提出了若干改良微藻代谢的新模式,以期对微藻代谢研究及后续的工程改造有所启示.     

铜绿紫球藻(Porphyridium aerugineum)755培养的研究

紫球藻是一种具有潜在应用价值的经济微藻,它的生长速率受各种环境因子的影响.本文研究了不同光强、光周期、盐度、NaHCO3浓度、葡萄糖浓度、培养方式等因子对铜绿紫球藻(Porphyridium aerugineum)755生长的影响,并确定其最佳的培养条件.此外还分析了该藻的吸收光谱,为其培养提供参考数据.     

微藻代谢工程改造研究进展及展望

微藻种类繁多,分布广泛,很多微藻能通过自身代谢生产油脂、色素、多糖等高价值产品.但通常情况下,微藻生产高价值产品时存在产物含量低以及细胞采收成本高等缺点,限制了微藻产品的实际应用.为了有效开发利用微藻资源,研究如何利用遗传改造技术选育藻株,提高其代谢物含量,并改善微藻采收效率十分重要.近年来,利用代谢工程改造微藻取得了显著进展,此外,微藻基因组编辑及合成生物学研究也不断深入,这些遗传改造技术的不断进步和创新,必将提高微藻重要代谢物的生产效率,以满足人类不断增长的能源、食品和制药工业需求.     

基于微藻培养处理畜禽养殖废水的研究进展

当前规模化畜禽养殖业排放含有大量氮磷、重金属和有机污染物的粪污废水,导致生态环境遭受严重的污染,治理畜禽废水的任务迫在眉睫。由于传统畜禽废水处理方式及应用存在较多不足,基于微藻生物技术处理废水的研究得到越来越多的关注。微藻是一种广泛存在于水体中的单细胞生物,具有高效的脱氮除磷及纳污能力,其主要利用同化作用吸附污水中的氮,通过磷酸化作用吸附、沉降磷,依靠细胞膜上的官能团对重金属进行富集。基于以上生理基础,大多数微藻的氮磷吸附率和重金属富集率可以高达80%。目前微藻对畜禽废水污染组分的处理的研究主要集中在氮磷、重金属,实际应用方式多为高效藻类塘、活性藻、固定化技术、光生物反应器等。但是微藻处理畜禽废水仍存在分子机理研究较少,生产实际经验不足等问题。基于微藻处理畜禽废水的机理,通过综述若干微藻去除氮磷、重金属等污染物的效率,总结国内外微藻废水处理技术的研究及存在问题,展望了微藻废水工程发展前景。     

生物技术研究引领中国微藻产业发展的六十年:回顾与展望

微藻是单细胞放氧光合作用微生物.据记载,早在1500年前的晋代,中国人就有食用微藻的传统,并尝试将其作为中药治疗疾病. 1959～1962年的三年困难时期,党和国家鼓励科学家开展小球藻替代粮食的研究,微藻生物技术开始得到发展. 20世纪80年代的"把螺旋藻作为全民蛋白质的补充"国家战略,为微藻生物技术的进步注入了创新活力.随着藻种选育技术、跑道式和管道式反应器的进步,以及微藻培养方式的根本性创新,我国的螺旋藻、小球藻、雨生红球藻和裸藻生物量接连取得根本性的突破,中国成为世界最大的微藻生产国.我国微藻生物技术研究将在引领产业降低生产成本、提高生产规模和效益的同时,引导建立微藻精准应用及环境治理的生物经济新模式.     

Microalgae aquaculture feeds

Microalgae feeds are currently used in relatively small amounts in aquaculture, mainly for the production of larvae and juvenile shell- and finfish, as well as for raising the zooplankton required for feeding of juvenile animals. The blue-green algaSpirulina is used in substantial amounts (over 100 t y^–1) as a fish and shrimp feed, and even larger markets can be projected if production costs could be reduced. Another potential large-scale application of microalgae is the cultivation ofHaematococcus for the production of the carotenoid astaxanthin, which gives salmon flesh its reddish color. In the long-term microalgae biomass high in lipids (omega-3 fatty acids) may be developed as substitutes for fish oil-based aquaculture feeds. In shrimp ponds the indigenous algal blooms supply a part of the dietary requirements of the animals, but it is difficult to maximize algal productivities. A separate algal production system could feed the shrimps and minimize the need for added feed. Bivalves feed essentially exclusively on marine microalgae throughout their life cycle. The development of cultivation technologies for such microalgae would allow the onshore production of these animals, with greatly improved product quality and safety.This paper was presented at the Symposium on Applied Phycology at the Fourth International Phycological Congress, Duke University.     

Microalgae as a raw material for biofuels production

Biofuels demand is unquestionable in order to reduce gaseous emissions (fossil CO₂, nitrogen and sulfur oxides) and their purported greenhouse, climatic changes and global warming effects, to face the frequent oil supply crises, as a way to help non-fossil fuel producer countries to reduce energy dependence, contributing to security of supply, promoting environmental sustainability and meeting the EU target of at least of 10% biofuels in the transport sector by 2020. Biodiesel is usually produced from oleaginous crops, such as rapeseed, soybean, sunflower and palm. However, the use of microalgae can be a suitable alternative feedstock for next generation biofuels because certain species contain high amounts of oil, which could be extracted, processed and refined into transportation fuels, using currently available technology; they have fast growth rate, permit the use of non-arable land and non-potable water, use far less water and do not displace food crops cultures; their production is not seasonal and they can be harvested daily. The screening of microalgae (Chlorella vulgaris, Spirulina maxima, Nannochloropsis sp., Neochloris oleabundans, Scenedesmus obliquus and Dunaliella tertiolecta) was done in order to choose the best one(s), in terms of quantity and quality as oil source for biofuel production. Neochloris oleabundans (fresh water microalga) and Nannochloropsis sp. (marine microalga) proved to be suitable as raw materials for biofuel production, due to their high oil content (29.0 and 28.7%, respectively). Both microalgae, when grown under nitrogen shortage, show a great increase (~50%) in oil quantity. If the purpose is to produce biodiesel only from one species, Scenedesmus obliquus presents the most adequate fatty acid profile, namely in terms of linolenic and other polyunsaturated fatty acids. However, the microalgae Neochloris oleabundans, Nannochloropsis sp. and Dunaliella tertiolecta can also be used if associated with other microalgal oils and/or vegetable oils.     

Benthic microalgae: comparisons of chlorophyll a in mesocosms and field sites

A mesocosm facility is being developed by the CSIRO Division of Fisheries to study the movement, fate and impact of pollutants in coastal marine environments. Initially, we are studying coastal habitats in S.W Australia that are subject to wave action. A 12 week experiment assessed changes in biotic and abiotic components of sediment brought from the field into mesocosms. In these sediments, benthic microalgae are the major primary producers. Microalgal standing stocks were measured as the concentration of chlorophyll a and phaeopigments in the top 2 cm of sediment, and these measures were compared among mesocosms and field sites. Significant increases in chlorophyll a and phaeopigments, increased numbers of species and a shift from episammic to periphytic diatoms were observed, possibly caused by decreased water motion in mesocosms or other containment effects. Results from statistical power analyses suggested that our sampling was sufficiently well replicated and successfully incorporated variation at small spatial and temporal scales. Sampling effort used in this experiment should form the basis for future work with benthic microalgae.     

Mechanisms of response to salinity in halotolerant microalgae

Summary A limited number of organic solutes are used by microalgae to adjust their internal osmotic pressure in response to changing external salinities. Glycerol and proline are used by the most extremely halotolerant algae. Only glycerol allows growth at salinities approaching saturation. In addition to organic osmoregulatory solutes, inorganic ions also play an important role in osmoregulation. The ability of microalgae to maintain intracellular ions at levels compatible with metabolic functions may set upper limits for their salt tolerance. Requirements for NaCl in the external medium for nutrient transport may define the lower salinity limits for growth observed for some euryhaline algae.Osmotic upshocks generally cause severe temporary inhibition of photosynthesis in euryhaline microalgae. Extensive osmotic downshocks have little effect on photosynthesis in microalgae with strong cell walls, while wall-less species appear to be more sensitive. Rapid glycerol synthesis takes place in response to increased external salinity inChlamydomonas pulsatilla both in light and dark. Starch supplies carbon for glycerol synthesis in the dark and also during the initial periods of inhibition of photosynthesis in the light. Turnover of osmoregulatory solutes such as glycerol and isofloridoside may be an important aspect of the osmoregulatory mechanism.At salinities beyond the growth limit for the green flagellateChlamydomonas pulsatilla, resting spores are formed that enable this alga to survive extreme salinities.     

Screening cultured marine microalgae for anticancer-type activity

Marine Cyanophyceae, and to a lesser extent other marine microalgae, are a promising source of new anticancer-type natural products. Microscopic forms that do not form mats or tufts in nature must be cultured in order to obtain sufficiently sized samples. Field collections of microalgae in intertidal and shallow subtidal tropical environments utilize hand collection and manipulation techniques into small-volume wide-mouth jars. Acclimation times in the laboratory environment are important in bringing new cultures into cultivation. Manipulation on agar plates has given the best success rate for obtaining unialgal cultures; sometimes these are obtained directly as axenic clones. These pure strains are cultured in an initial volume of 3 L to give sufficient material for pharmacological screening. The extracts are evaluated in a series of mechanism-based anticancer screens, including protein kinase C (PKC), protein tryosine kinase (PTK) and inosine monophosphate dehydrogenase (IMPDH). More that 501 extracts have been screened in these three assay areas, and have yielded 23 active to IMPDH, 9 to PKC, and 9 to PTK. The extract of one cultured microalga which was active to PTK,Poteriochromonas malhamensis, has yielded a novel chlorosulfolipid, whose structure is discussed. Future efforts will (a) target less well explored groups of microalgae including several orders of cyanophyceae as well as field collections of cryptophytes and chrysophytes, and (b) complement mechanism-based screening with cancer cell cytotoxicity screening.     

Screening of microalgal culture media for the presence of algicidal compounds and isolation and identification of two bioactive metabolites,excreted by the cyanobacteria <Emphasis Type="Italic">Nostoc insulare</Emphasis> and <Emphasis Type="Italic">Nodularia harveyana</Emphasis>

Culture medium extracts obtained from 115 culture media of 35 different microalgae species were screened for the presence of algicidal compounds, in particular for compounds which are cytotoxic to Arthrospira (Spirulina) laxissima. In agar plate diffusion tests and in a test system combining thin layer chromatography (TLC) with the use of an aqueous suspension of living A. laxissima cells as spray reagent, 14 microalgae species were found with cytotoxic activity of different intensity to A. laxissima. In a so-called TLC plate diffusion test, using A. laxissima and other microalgae as test organisms, the culture medium extracts of Nodularia harveyana and Nostoc insulare possessed the highest strength and range of algicidal activity. The algicidal compound in the culture medium extracts of Nodularia harveyana was shown to be norharmane (9H-pyrido(3,4-b)indole), a known indole alkaloid. The main algicidal compound in culture medium extracts of Nostoc insulare was identified as 4,4′-dihydroxybiphenyl. The possible applicability of both compounds as therapeutics or as useful agents for removing cyanobacterial water blooms or for developing new antifouling systems is discussed.     

Solar energy conversion efficiencies in photosynthesis: Minimizing the chlorophyll antennae to maximize efficiency

The theoretical maxima of solar energy conversion efficiencies and productivities in oxygenic photosynthesis are evaluated. These are contrasted with actual measurements in a variety of photosynthetic organisms, including green microalgae, cyanobacteria, C4 and C3 plants. Minimizing, or truncating, the chlorophyll antenna size of the photosystems can improve photosynthetic solar energy conversion efficiency and productivity up to 3-fold. Generation of truncated light-harvesting chlorophyll antenna size (tla) strains, in all classes of photosynthetic organisms would help to alleviate excess absorption of sunlight and the ensuing wasteful dissipation of excitation energy, and to maximize solar-to-product energy conversion efficiency and photosynthetic productivity in high-density mass cultivations. The tla concept may find application in the commercial exploitation of microalgae and plants for the generation of biomass, biofuels, chemical feedstocks, as well as nutraceuticals and pharmaceuticals.     

Noctiluca scintillans may act as a vector of toxigenic microalgae

Noctiluca scintillans food vacuoles containing toxigenic microalgae of the genera Dinophysis and Pseudo-nitzschia are reported in samples from the Galician Rías Baixas (NW Spain). N. scintillans may play an important role in the population dynamics of toxigenic microalgae blooms, and may act as a vector of phycotoxins to higher trophic levels. The harmful effects of Noctiluca in natural shellfish beds and/or aquaculture sites may be magnified if cells are loaded with toxigenic microalgal prey.     

Removal of nitrogen and phosphorus from wastewater using microalgae immobilized on twin layers: an experimental study

Removal of nitrogen and phosphorus from wastewater by two green microalgae (Chlorella vulgaris and Scenedesmus rubescens) was investigated using a novel method of algal cell immobilization, the twin-layer system. In the twin-layer system, microalgae are immobilized by self-adhesion on a wet, microporous, ultrathin substrate (the substrate layer). Subtending the substrate layer, a second layer, consisting of a macroporous fibrous tissue (the source layer), provides the growth medium. Twin-layers effectively separate microalgae from the bulk of their growth medium, yet allow diffusion of nutrients. In the twin-layer system, algae remain 100% immobilized, which compares favourably with gel entrapment methods for cell immobilization. Both microalgae removed nitrate efficiently from municipal wastewater. Using secondary, synthetic wastewater, the two algae also removed phosphate, ammonium and nitrate to less than 10% of their initial concentration within 9 days. It is concluded that immobilization of C. vulgaris and S. rubescens on twin-layers is an effective means to reduce nitrogen and phosphorus levels in wastewater.