Effect of carbon source on growth and lipid accumulation in Chlorella sorokiniana GXNN01

Heterotrophic culture of microalgae to develop methods of increasing biomass productivity and storage lipids has brought new insight to commercial biodiesel production. To understand the relationship between heterotrophy and lipid production, the effects of carbon sources on the growth and lipid accumulation of Chlorella sorokiniana GXNN01 was studied. The alga exhibited an increased growth rate in response to the addition of carbon sources, which reached the stationary phase after 48 h at 30A degrees C. In addition, glucose and NaAc had a significant effect on the lipid accumulation during the early-stationary phase. Specifically, the lipid content was 0.237 +/- 0.026 g g(-1) cell dry weight and 0.272 +/- 0.041 g L-1 when glucose was used as the carbon source, whereas the lipid content reached 0.287 +/- 0.018 g g(-1) cell dry weight and 0.288 +/- 0.008 g L-1 when NaAc was used as the carbon source. The neutral lipid content was found to first decrease and then increase over time during the growth phase. A glucose concentration of 20 mmol L-1 gave the maximal lipid yield and the optimum harvest time was the early-stationary phase.

Effect of iron on growth and lipid accumulation in Chlorella vulgaris

The economic feasibility of algal mass culture for biodiesel production is enhanced by the increase in biomass productivity and storage lipids. Effect of iron on growth and lipid accumulation in marine microalgae Chlorella vulgaris were investigated. In experiment I, supplementing the growth media with chelated FeCl3 in the late growth phase increased the final cell density but did not induce lipid accumulation in cells. In experiment II, cells in the late-exponential growth phase were collected by centrifugation and re-inoculated into new media supplemented with five levels of Fe3+ concentration. Total lipid content in cultures supplemented with 1.2 x 10(-5) mol L-1 FeCl3 was up to 56.6% biomass by dry weight and was 3-7-fold that in other media supplemented with lower iron concentration. Moreover, a simple and rapid method determining the lipid accumulation in C. vulgaris with spectrofluorimetry was developed. (c) 2007 Elsevier Ltd. All rights reserved.

两种真核微藻逆境响应关键基因的调控机理研究

非生物逆境胁迫严重影响植物的生长发育和作物的产量。解析逆境下植物体基 因表达及信号传导网络调控机制对于阐明植物的适应性反应及培育耐逆性作物具有 重要理论和现实意义。 雨生红球藻（Haematoccoccus pluvialis）通过累积虾青素来适应胁迫环境，茉莉 酮酸甲酯（methyl jasmonate，MJ）和赤霉素（gibberellins，GA）对植物胁迫适应过 程中相关基因的诱导表达起到重要的调控作用。本文选取 H. pluvialis 作为出发株， 研究了 MJ 和 GA 对虾青素合成途径关键酶 β-胡萝卜素酮化酶基因的调控作用。 在其中一种 H. pluvialis 中克隆获得了三种不同的 β-胡萝卜素酮化酶基因。通过基 因组步移，获得了三种 β-胡萝卜素酮化酶的5’ 侧翼序列（5’-flanking region），其 中存在着多样的顺式作用元件，包括 MJ 和 GA 的顺式作用位点。进一步的实验 表明，MJ 和 GA 的诱导处理，可以促进 H. pluvialis 中虾青素的累积；同时，MJ 和 GA 调控了三种 β-胡萝卜素酮化酶基因的转录水平。 南极小球藻（Chlorella vulgaris NJ-7）可以在较大温度和盐度变化范围内存活， 是研究生物胁迫适应机理的理想模式生物。对数期的 C. vulgaris NJ-7 主要的脂肪酸

基于28S rDNA序列的鞘藻目系统发育研究

作者进行了较广泛的样品采集,通过实验分离纯化培养得到多个鞘藻目种类的株系,并采用PCR技术新获得鞘藻目2属8个种类的部分28S rDNA序列,连同GenBank中的另两条序列,分析的物种涵盖了鞘藻目中的每个属。通过比较分析绿藻纲中包括此10条序列的共36个种类的同一基因序列,并选取Trebouxiophyceae中的椭圆小球藻(Chlorella ellipsoidea)和Fusochloris perforata作外类群,运用多种方法构建分子系统树,包括邻接法(Neighbor-Joining)、最大简

叶绿素荧光作为Poterioochromonas malhamensis光合潜能指标的研究

通过返回式卫星上的空间通用生物培养箱，搭载了由金藻（Poterioochrmonasmal-hamensis）和小球藻（Chlorella）构成的微二元生物封闭系统．研究了P.malhamensis在不同营养和光照条件下光合潜能的变化．在仅有光照没有饵料生物时，叶绿素荧光比植Fv／Fm为0．6;在有光照和有饵料生物存在时，Fv／Fm下降迅速，培养一天后，降至开始时的1／10.结果表明，叶绿素荣光比值Fv／Fm能迅速而准确地反映其细胞的光合代谢状态．此结果为进一步研究微二元生物封闭系统的空间生物学效应提供了

密度和温度对萼花臂尾轮虫产卵量和混交雌体的影响

用小球藻(Chlorella sp.)为食培养萼花臂尾轮虫(Brachionus calyciflorus),食物浓度约1×10~6cells/mL,温度25℃,光照强度约40001x,昼长比LD=18:6。在1.0mL、0.5mL和0.25mL培养液中同时进行单个体和群体培养。结果发现:1)单个体培养时每个母体平均产卵量分别为12.0,13.8和7.8个;后代个体中混交雌体的百分比分别是46.38％,53.49％和55.83％。2)群体培养时,每个母体平均产卵量分别为8.7、3.1和2.65个,随密度增

小球藻应用研究动态

<正> 小球藻(Chlorella)是一类普生性单细胞绿藻,种类繁多。它们能适应于不同的生长环境,在人工培养基中生长良好,除能利用光能自养外,还可以异养培养。小球藻富含多种有用成分,在特定条件下,其代谢途径改变,积累的产物也不同。因此,长期以来,小球藻不仅是生物学研究中优良的实验材料,而且是引入注目的开发利用的对象。在日、苏、美、英、东欧、以色列和我国台湾省都在进行这方面的研究,尤其日本更为活跃。本文简要介绍近几年来国外有关小球藻应用研究的一些情况,目的在于交流信息,促近我国小球藻资源的开发利用,为经济建

Lysis of Aphanizomenon flos-aquae (Cyanobacterium) by a bacterium Bacillus cereus

A phytoplankton-lytic (PL) bacterium, Bacillus cereus, capable of lysing the bloom-forming cyanobacterium. Aphanizomenon flos-aquae was isolated from Lake Dianchi of Yunnan province, China. This bacterium showed lytic activities against a wide range of cyanobacteria/algae, including A. flos-aquae, Microcystis viridis, Microcystis wesenbergi, Microcystis aeruginosa, Chlorella ellipsoidea, Oscillatoria tenuis, Nostoc punctiforme, Anabaena flos-aquae, Spirulina maxima, and Selenastrum capricornutum. Chlorophyll a contents, phycocyanin contents, and photosynthetic activities of the A. flos-aquae decreased evidently in an infected culture for a period. Bacterium B. cereus attacked rapidly A. flos-aquae cells by cell-to-cell contact mechanism. It was shown that the lysis of A. flos-aquae began with the breach of the cyanobacterial cell wall, and the cyanobacterial cell appeared abnormal in the presence of the PL bacterium. Moreover, transmission electron microscope examinations revealed that a close contact between the bacterium and the cyanobacterium was necessary for lysis. Some slime extrusions produced from B. cereus assisted the bacterial cells to be in close association with and lyse the cyanobacterial cells. These findings suggested that this bacterium could play an important role in controlling the Aphanizomenon blooms in freshwaters. (c) 2006 Elsevier Inc. All rights reserved.

Physico-chemical properties of alkaline phosphatases released by a planktonic crustacean, Daphnia magna (Cladocera)

Our studies investigated the physico-chemical properties of alkaline phosphatase excreted by D. magna. This cladoceran mainly released alkaline phosphatase, though it also released a small amount of acid phosphatase. The alkaline phosphatase showed a broad pH optimum (8.05-10.0), and had a broad optimum temperature (30-35 degrees C) with a temperature coefficient (Q(10)) of 2.45. The K-m of the enzyme is 0.15 +/- 0.02 mM when p-nitrophenyl phosphate is used as a substrate, and the V-max is 0.43 +/- 0.01 mu M pNP mg(-1) DW h(-1). Even though alkaline phosphatase had been incubated in chloroform saturated with WC medium for 13 days, its activity was 54% that of the original. The enzyme was strongly inactivated by EDTA, and appeared to be zinc dependent. The alkaline phosphatase activity remained constant when D. magna was fed different quantities of Chlorella sp. The sensitivity of D. magna phosphatase activity to phosphate was time-dependent. During the first 16 hrs, the enzyme was insensitive to phosphate addition, after 24 hrs incubation the enzyme became sensitive to phosphate addition.

The vertical microdistribution of cyanobacteria and green algae within desert crusts and the development of the algal crusts

Substantial amounts of algal crusts were collected from five different desert experimental sites aged 42, 34, 17, 8 and 4 years, respectively, at Shapotou ( China) and analyzed at a 0.1 mm microscale of depth. It was found that the vertical distribution of cyanobacteria and microalgae in the crusts was distinctly laminated into an inorganic-layer (ca. 0.00 - 0.02 mm, with few algae), an algae-dense-layer ( ca. 0.02 - 1.0 mm) and an algae-sparse-layer ( ca. 1.0 - 5.0 mm). It was interesting to note that in all crusts Scytonema javanicum Born et Flah ( or Nostoc sp., cyanobacterium), Desmococcus olivaceus (Pers ex Ach., green alga) Laundon and Microcoleus vaginatus Gom. ( cyanobacterium) dominated at the depth of 0.02 - 0.05, 0.05 - 0.1 and 0.1 - 1.0 mm, respectively, from the surface. Phormidium tenue Gom. ( or Lyngbya cryptovaginatus Schk., cyanobacterium) and Navicula cryptocephala Kutz.( or Hantzschia amphioxys (Ehr.) Grun. and N. cryptocephala together, diatom) dominated at the depth of 1.0 - 3.0 and 3.5 - 4.0 mm, respectively, of the crusts from the 42 and 34 year old sites. It was apparent that in more developed crusts there were more green algae and the niches of Nostoc sp., Chlorella vulgaris Beij., M. vaginatus, N. cryptocephala and fungi were nearer to the surface. If lichens and mosses accounted for less than 41.5% of the crust surface, algal biovolume was bigger when the crust was older, but the opposite was true when the cryptogams other than algae covered more than 70%. In addition to detailed species composition and biovolume, analyses of soil physicochemical properties, micromorphologies and mineral components were also performed. It was found that the concentration of organic matter and nutrients, electric conductivity, silt, clay, secondary minerals were higher and there were more micro-beddings in the older crusts than the less developed ones. Possible mechanisms for the algal vertical microdistribtion at different stages and the impact of soil topography on crust development are discussed. It is concluded that biomethods ( such as fine species distribution and biovolume) were more precise than mineralogical approaches in judging algal crust development and thus could be a better means to measure the potentiality of algal crusts in desert amelioration.

The effects of fresh and decomposed Microcystis aeruginosa on cladocerans from a subtropic Chinese Lake

We studied in the laboratory the population growth rates of four cladocerans fed both with decomposed Microcystis aeruginosa and with a mixture of fresh colonial M. aeruginosa and Scenedesmus obliquus. The neonates of Diqphanosoma brachyurum and Daphnia carinata were able to develop into adults when they were fed with <64mum decomposed M. aeruginosa, while those of Moina micrura could not use decomposed M. aeruginosa. The population growth rate of the largest species, D. carinata, was less affected by the presence of fresh colonial M. aeruginosa than the other three species. D. carinata obtained the highest growth rate at a biomass level of 10 mg L-1 fresh colonial M. aeruginosa, indicating that, to some extent, it can use colonial M. aeruginosa at a size range of 64-112mum. The population growth rate of M. micrura was negatively correlated with fresh colonial M. aeruginosa within a range of 10-100 mg L-1. The population growth rates of D. brachyurum and Ceriodaphnia cornuta were remarkably decreased by fresh colonial M. aeruginosa, although no significant difference was found within the M. aeruginosa biomass range of 10-100 mg L-1 for either cladoceran. At a biomass level of 50 mg L-1 M. aeruginosa, the population growth rates of the four cladocerans positively correlated with S. obliquus biomass within a range of 0.1-5.0 mg L-1. Our results indicate that the zooplankton community under bloom condition is shaped by the quantity of both M. aeruginosa and other edible algae.

Effect of available food and temperature on the growth and reproduction of Daphnia rosea

Population parameters of Daphnia rosea were studied at various concentrations of Chlorella sp. (0.25, 0.75 and 3.0 mg C l(-1)) at several temperatures (20, 25, 28, and 30 degrees C) in the laboratory. Although there were some differences in the degrees of the effects of the various temperature-food combinations, both food and temperature exerted influences on almost all of the main population parameters of D. rosea. At a water temperature of 28 degrees C, growth and reproduction were reduced, and at the lowest food level (0.25 mgC l(-1)), reproduction failed. D, rosea did not survive at 30 degrees C in spite of abundant food supply, indicating that 30 degrees C is a physiological limit. A positive relationship between body length and brood size was recognized at high and medium food levels. The slope of the regression was the highest at the highest food level and at the lowest temperature (20 degrees C). The low food level exerted a negative influence on the net reproductive rate by lowering the size of egg-bearing females, by decreasing the brood size of each size class, by decreasing the brood number per female, and by increasing the period of empty brood chamber. High water temperature (28 degrees C) also exerted a negative influence on the net reproductive rate in a similar way. For the better understanding of the key factors driving the midsummer dynamics of daphnids in the field, it may be of crucial importance to compare the population parameters of the field populations with experimentally derived values under controlled conditions of food concentration and temperature.

The integrative expression of GUS gene driven by FCP promoter in the seaweed Laminaria japonica (Phaeophyta)

In this study, the background activity of beta-glucuronidase (GUS) was analyzed histochemically and fluorometrically in the negative control of Laminaria japonica (Phaeophyta) thalli, showing low level of activity. GUS gene transformation without selectable gene in L. japonica was performed using four different promoters, i.e., Cauliflower mosaic virus 35S promoter (CaMV35S) from cauliflower mosaic virus, ubiquitin promoter (UBI) from maize, adenine-methyl transfer enzyme gene promoter (AMT) from virus in green alga Chlorella, and fucoxanthin chlorophyll a/c-binding protein gene promoter (FCP) from diatom Phaeodactylum tricornutum. The GUS transient activity was determined fluorometrically after bombarding sliced parthenogenetic sporophytes explants, and it was found that the activity resulting from CaMV35S and FCP promoters (in 114.3 and 80.6 pmol MU min(-1) (mg protein)(-1), respectively) was higher than for the other two promoters. The female gametophytes were bombarded and regenerated parthenogenetic sporophytes. FCP was the only promoter that resulted in detectable GUS chimeric expression activity during histochemical staining and polymerase chain reaction. Results of Southern blot showed that GUS gene was integrated with the L. japonica genome.

Production of astaxanthin from Haematococcus in open pond by two-stage growth one-step process

We have developed a two-stage growth one-step process for cultivation of Haematococcus using a self-designed system that mimics an open pond in the natural environment. The characteristics of this process are green vegetative cell growth and cysts transformation and pigment accumulation that proceed spontaneously and successively in one open photobioreactor. Four strains of Haematococcus (H. pluvialis 26; H. pluvialis 30; H. pluvialis 34; H. pluvialis WZ) were cultured in this imitation system for a duration of 12 days. The changes in cell density and medium pH were closely monitored, and the astaxanthin content and yield of the four Haematococcus strains were measured at the end of 12 days of cultivation. Two of the strains, H. pluvialis 26 and H. pluvialis WZ, were selected as strains suitable for mass culture, resulting in the astaxanthin yield of 51.06 and 40.25 mg L-1 which are equivalent to 2.79 and 2.50% of their dry biomass respectively. Based on the laboratory work, 6 batch cultures of H. pluvialis WZ were conducted successfully to produce astaxanthin in two 100 m(2) open race-way pond by two-stage growth one-step process. The astaxanthin content ranged from 1.61 to 2.48 g 100 g(-1) dry wt., with average astaxanthin content of 2.10 g 100 g(-1) dry wt. Compared with the one-stage production of astaxanthin based on continuous culture, the superiority of our process is that it can accumulate much more astaxanthin in red cysts. Compared with two-stage production of astaxanthin, the advantage of our process is that it does not need to divide the production process into two parts using two bioreactors. The presented work demonstrates the feasibility for producing astaxanthin from Haematococcus using a two-stage growth one-step process in open pond, culture systems that have been successfully used for Spirulina and Chlorella mass culture. The future of Haematococcus astaxanthin production has been also discussed. (C) 2009 Elsevier B.V. All rights reserved.

A simple and low-cost airlift photobioreactor for microalgal mass culture

A simple, low-cost, and efficient airlift photobioreactor for microalgal mass culture was designed and developed. The reactor was made of Plexiglas, and composed of three major parts: outer tube, draft tube and air duct. The fluid-dynamic characteristics of the airlift reactor were studied. The system proved to be well suited to the mass cultivation of a marine microalga, Chlorella sp. In batch culture, the biomass volumetric output rate of 0.21 g l(-1) d(-1) was obtained at the superficial gas velocity of 4 mm s(-1) in the draft tube.