Role of fulvic acid on lead bioaccumulation by Chlorella kesslerii

To better understand the relationship between lead speciation and bioavailability in natural freshwaters, the interaction of lead with the freshwater alga Chlorella kesslerii was studied in the presence of the Suwannee River fulvic acid (SRFA). Special attention was paid to direct interactions of the fulvic acid on the algae, as well as potential physiological (membrane permeability and algal metabolism) influences. Lead-free ion concentration measurements were carried out using a novel ion-selective electrode. Pb uptake decreased in the presence of SRFA with respect to noncomplexed Pb, but uptake fluxes, cellular Pb, Pb bound to the transport sites, and total adsorbed Pb were all higher than predicted from Pb2+ activities, in accordance with the free ion activity model (FIAM). The discrepancies between the observed values and those predicted by the FIAM in the presence and absence of synthetic ligands increased with increasing concentration of SRFA. Several hypotheses were examined to explain the observed differences. No contributions of labile and/or hydrophobic Pb-SRFA complexes were found. Furthermore, direct biological effects, including variations in membrane permeability or algal metabolism, could not account for the observations. On the other hand, changes in the algal surface charge due to SRFA adsorption seemed to account, at least partially, for the observed increase in lead uptake in the presence of SRFA as compared to that corresponding to the same Pb2+ concentration in the presence of synthetic ligands.     

响应面法优化小球藻培养基

为了提高小球藻的生物量,对BG11培养基的成分进行了响应面优化。通过单因素实验筛选出了适合小球藻生长的最佳碳源、氮源分别为葡萄糖和尿素,并发现适量添加海绿素可显著促进小球藻的生长。利用Minitab软件设计Plackett-Burman实验筛选出了影响小球藻生长的三个最重要因子;通过Box-Behnken实验及响应面分析确定了三个因子的最佳浓度:磷酸氢二钾58mg/L,硫酸镁162mg/L,海绿素198μL/L。用优化后的培养基培养小球藻,48h后的藻细胞干重达10.09g/L,比优化前提高了61.2%,油脂及蛋白质产量分别达3.62和3.81g/L。     

小球藻营养成分积累的磁处理强化

对磁场作用下小球藻Chlorellavulgaris生长和营养成分的变化进行研究,发现不同磁感应强度的处理对C.vulgaris的生长和营养成分的影响不同,弱磁感应强度处理刺激C.vulgaris的生长,0.05T以上的强磁感应强度表现出一定的的抑制作用;弱磁剂量处理下糖含量,蛋白含量有所增加,脂肪含量略有减少;强磁剂量处理下糖含量,蛋白含量变化较小,脂肪含量明显增加;磁处理改变了C.vulgaris中的氨基酸的组成,氨基酸含量都有所增加,尤其10mT处理下必需氨基酸增加非常明显;在10mT磁处理下VB1,VB2和VC含量显著增加,0.5T处理中,VB2的含量有所减少,VB1和VC增幅很大。磁处理强化培养是进一步提高小球藻营养价值的一种较有效手段。     

Fat mimetic capacity of Chlorella vulgaris biomass in oil-in-water food emulsions stabilized by pea protein

Vegetable proteins proved to be good emulsifiers for food emulsions with dietetic advantages. The use of these emulsions as carriers for healthy ingredients, such as colourings, with antioxidant and other beneficial properties, is an interesting subject.In this work, the capacity of the biomass of the microalga Chlorella vulgaris (which has been widely used as a food supplement) as a fat mimetic, and its emulsifier ability, was evaluated. Pea protein emulsions with C. vulgaris addition (both green and orange – carotenogenic) were prepared at different protein and oil contents. The rheological properties of the respective food emulsions were measured in terms of the viscoelastic properties and steady state flow behaviour and texture properties. It was observed that the two microalgal forms evidenced a fat mimetic capacity in these emulsions, the performance of the green stage of this C. vulgaris organism was significantly (p < 0.05) better than the orange stage.     

光合细菌与小球藻复合处理豆制品废水

对光合细菌与小球藻复合处理豆制品有机废水进行了研究.结果表明,第一步用光合菌处理后,CODcr、BOD5分别降至250mg/L和185mg/L,平均去除率分别达89.3%和90.9%;第二步用小球藻与光合细菌的混合液处理后,CODcr和BOD5分别降至84mg/L和51mg/L,平均去除率分别达66.4%和72.4%.两步复合处理的CODcr、BOD5的总去除率分别达到96.4%和97.5%.     

Physicochemical Studies of Hard-to-Cook Beans (Phaseolus vulgaris)

Model aqueous systems were used for the study of the cooking quality of beans (Phaseolus vulgaris). These systems were created using graded contents of calcium and magnesium ions, in a ratio of 4:1, to prepare aqueous media with cation content corresponding to 0–400 mg litre^-1 of calcium carbonate. The model systems were used to measure the quality of boiled beans in water of low and high divalent cation content. A boiling time of 60 min was used and the hardness of the boiling beans was measured by an Instron Universal Testing Machine. Cooking of beans in water of low divalent cation content equivalent to 0–50 mg litre^-1 CaCO₃ resulted in well-boiled beans for both types (easy-to-cook and hard-to-cook) of beans. Boiling in water of high divalent cation content led to the formation of very hard beans for both types of bean, while boiling in water of moderate divalent cation content (normal drinking water: 150–250 mg litre^-1 CaCO₃) differentiated between the two categories of beans. These results were further tested by adsorption experiments with divalent cations, on beans boiled (a) in different proportions of boiling water, and (b) in model aqueous systems. The divalent cation content of boiling water and the phytic acid content of the beans proved to be the crucial factors in the hard-to-cook phenomenon of beans. © 1997 SCI.     

Physicochemical aspects of synthetic food production]

The authors discuss the general approach to the problem of the protein architecture and the working of proteins to synthetic foods. They present the main results from relevant studies on the compatibility and interactions of proteins and polysaccharides in aqueous media and deal with possibilities of influencing the structure formation and the physical properties of gels of given composition.     

Effects of parameters affecting biomass yield and thermal behaviour of Chlorella vulgaris

Conventional fossil fuels are facing a global challenge which lead scientists to explore alternative fuel production from biological sources. The algae-based fuels are gaining rapid attention as it has potential to replace petroleum-based fuels. An indigenous high lipid producing microalgae was isolated from a freshwater pond in the KwaZulu-Natal province of South Africa. The isolate was later identified as Chlorella vulgaris, based on partial 28S large subunit ribosomal RNA gene sequence. The growth kinetics, pyrolytic characteristics and photosynthetic efficiency of Chlorella was evaluated in vitro. The optimized conditions for higher biomass yield of the selected strain were at 4% CO(2), 0.5 g l(-1) NO(3) and 0.04 g l(-1) PO(4), respectively. The pulse amplitude modulation results indicated that C. vulgaris could withstand a light intensity ranging from 150 to 350 μmol photons m(-2)s(-1). Further increase in light intensity resulted in a decline of the electron transport rate. Carbon fixation rate, lipid content and calorific value of C. vulgaris was 6.17 mg l(-1)h(-1), 21% and 17.44 kJ g(-1), respectively. The pyrolitic studies under inert atmosphere at different heating rates of 15, 30, 40 and 50°C min(-1) from ambient temperature to 800°C showed that the overall final weight loss recorded for the four different heating rates was in the range of 78.9-81%. These studies could be useful to appraise the biofuel potential of the isolated C. vulgaris strain, which can later be taken for pilot scale production.     

Release of reduced inorganic selenium species into waters by the green fresh water algae Chlorella vulgaris

The common green fresh water algae Chlorella vulgaris was exposed to starting concentrations of 10 μg/L selenium in the form of selenate, selenite, or selenocyanate (SeCN(-)) for nine days in 10% Bold's basal medium. Uptake of selenate was more pronounced than that of selenite, and there was very little uptake of selenocyanate. Upon uptake of selenate, significant quantities of selenite and selenocyanate were produced by the algae and released back into the growth medium; no selenocyanate was released after selenite uptake. Release of the reduced metabolites after selenate exposure appeared to coincide with increasing esterase activity in solution, indicating that cell death (lysis) was the primary emission pathway. This is the first observation of biotic formation of selenocyanate and its release into waters from a nonindustrial source. The potential environmental implications of this laboratory observation are discussed with respect to the fate of selenium in impacted aquatic systems, the ecotoxicology of selenium bioaccumulation, and the interpretation of environmental selenium speciation data generated, using methods incapable of positively identifying reduced inorganic selenium species, such as selenocyanate.     

Investigation of nutraceutical potential of the microalgae Chlorella vulgaris and Arthrospira platensis

The microalgae Chlorella vulgaris and Arthrospira platensis were evaluated as nutraceuticals. It was observed that Arthrospira platensis is richer in saturated fatty acids (FA) and Chlorella vulgaris richer in monounsaturated FA. Within polyunsaturated FA (PUFA), n3 PUFA content was below 1% in Arthrospira sp and over 10% in Chlorella vulgaris. This microalga had the lowest polyphenolic content. The highest value was found in the aqueous extract of Arthrospira platensis, 334 ± 32 mg GAE per 100 g dw. Regarding DPPH, only aqueous extracts of Chlorella vulgaris yielded antioxidant activity with an inhibitory activity of 80 ± 1%. ABTS results showed stronger inhibition through the aqueous extracts than through the ethanolic extracts, 89%–93% vs. 24%–32%. Concerning cytotoxicity, ethanolic extracts of Chlorella vulgaris induced a cell viability decrease of approximately 80%. The biochemical characterisation and bioactivity assessment of Chlorella vulgaris and Arthrospira platensis showed that these microalgae have potential for nutraceutical applications.     

异养小球藻发酵液上清液回用的试验研究

采用发酵液上清液进行小球藻培养试验研究。以小球藻的生物量为指标,通过上清液回用比例试验、单因素试验和L_9(3~4)正交试验进行配方优化,考察利用上清液培养小球藻的可行性。结果表明:上清液回用比例为30%(占配料用水量)处理效果最佳,在此基础上的配方优化结果为酵母粉2 g/L、K_2HPO_40.3 g/L、Mg SO_40.2 g/L、微量元素母液0.5 m L;在此工艺条件下,上清液首次回用小球藻在发酵末期的生物量比未添加上清液对照组高71%左右,二次、三次回用依次降低,但仍高于对照组,进一步验证了小球藻在优化配方下能够有效利用小球藻发酵液上清液促进自身生长,并且通过发酵液上清液的循环使用,可以节省30%的用水量、40%的营养物质(不含糖)用量并且可以减少环境污染。     

Supplementation of Spirulina platensis and Chlorella vulgaris Algae into Probiotic Fermented Milks

Viability of probiotic bacteria during the production and storage of fermented milks is the most important topic of discussion in the dairy industry. Addition of microalgae into milk for the production of fermented milk in order to enhance the viability of probiotics has been the subject of recent research. Spirulina and Chlorella are the most widely noted microalgae for fermented milks. They affect not only the viability of probiotics in final product but also the sensory attributes of them. Incorporation of microalgae into probiotic fermented milks along with enhancing the viability of probiotics would increase their functional characteristic. This is because they contain a wide range of nutrients and nutraceuticals and are considered as “functional food.” This article reviews the effects of supplementation of Spirulina platensis and Chlorella vulgaris into probiotic fermented milks on their different quality characteristics.     

Chlorella vulgaris biomass used as colouring source in traditional butter cookies

A study was undertaken to determine the effects of Chlorella vulgaris biomass as a colouring ingredient in traditional butter cookies. The cookies were manufactured at a pilot scale and stored for 3 months at room temperature, protected from light and air. The effects of C. vulgaris incorporation on the biscuits' colour were tested weekly during the first month, and monthly afterwards, for a total period of 3 months. C. vulgaris cookies presented an accentuated green tonality, which increased with the quantity of added biomass. The colour parameters of the cookies remained very stable along the storage period. The texture of the cookies was also evaluated, and a significant increase of their firmness was evidenced with an increase of added microalgal biomass.Industrial relevanceThis work is set out as an example of the possibility of imparting a green colour relatively non-perishable food product, using a naturally occurring product. Green colouring is relatively difficult to impart, especially when using only natural products. Chlorella sp. has been and is used as a food supplement, and the authors found that the stable non-perishable tonalities obtained were agreeable to the consumer. It is therefore concluded that a possibility of developing similar products exists.     

序列相似性网络聚类与蛋白质家族划分

图聚类法是利用蛋白质序列信息推断其家族分类的有力手段。对于蛋白质数据集中家族内外存在着如同许多超家族一样的复杂关系,图聚类法达到较好表现必须两因素,1)输入的相似性图需要包含有足够的用于分类的信息;2)需要稳健的算法以识别被隐藏在相似性图中的模糊集团。作者测试模块度最优算法Contraction-Dilation(CD)算法,采用来自于Pfam中的具有高度序列差异的烯醇酶宗族作为测试数据集。结果表明使用CD算法在相关参数与相似性图比较恰当的情况下,得到聚类结果与Pfam中高度一致。该算法能在一般情况下,使用最佳参数附近较宽范围仍能表现出较好性能。     

紫外辐射对小球藻光合性能及油脂积累的影响

在紫外辐射剂量0～80 mJ/cm~2的条件下,探究紫外辐射对小球藻生长、光合性能和油脂积累的影响,利用荧光定量PCR测定藻细胞内与油脂合成相关基因的表达情况,同时采用气相色谱质谱联用测定小球藻油的脂肪酸组成及含量。结果表明:在最佳辐射剂量40 mJ/cm~2条件下,小球藻的生物量达到515 mg/L,光合性能维持在较高水平,Fv/Fm、Y(Ⅱ)、油脂含量、油脂产量分别达到0.588、0.594、46%、237 mg/L。相对于对照组,40 mJ/cm~2剂量的小球藻的油脂含量、油脂产量分别提高了39.40%和39.22%,accD和gapA的相对表达量分别提高了约2.5倍和5倍,Me、Pk相对表达量基本不变。40 mJ/cm~2剂量的小球藻油中单不饱和脂肪酸含量较高,达到40.17%,比对照组提高了16.5%,有利于生物柴油的生产,实际应用价值较高。     

不同培养模式对微藻Chlorella vugaris代谢与蛋白质组分的影响

研究不同培养模式对小球藻蛋白合成的影响。分别采用自养、异养和混养模式培养小球藻生产蛋白质。结果为混养时藻细胞更易积累生物量,其比生长速率和产率高达0.526 d-1和0.318mg/(L·d),且其蛋白质质量分数和产率分别为35.6%和0.097 g/(L·d),自养时蛋白质质量分数却最高为52.1%;3种方式培养小球藻均含18种氨基酸,且必须氨基酸比例均超过总的40.0%;异养和混养方式下各氨基酸组成比例基本相似,而与自养时相比,Cys-s、Tyr和Met比例差异显著,Cys-s比例分别高了约78.57%,而Tyr及Met分别低27.59%和33.33%左右。营养方式显著影响小球藻蛋白质合成及氨基酸组成比例。     

稀土元素La和Ce对小球藻生长的影响

本文以普通小球藻(Chlorella vulgaris)作为受试藻种,研究了硝酸镧和硝酸铈对其生长的影响,旨在探讨稀土化合物用于小球藻培养的方法和效果。具体实验包括：在藻类培养基中添加不同浓度的稀土硝酸盐,定时取样测定培养物光密度,绘制生长曲线并计算比生长速率(μ),测定细胞密度最大时的干物质含量、叶绿素含量、类胡萝卜素含量以及可溶性糖含量。通过实验得出：10-3~10-6 mM的稀土元素在培养早期能够促进小球藻的细胞增殖,但随着培养时间延长促进作用减弱,比生长速率与对照组的差异逐渐缩小;10-3 mM La可将叶绿素a和b的含量分别提高24.46%和28.51%,10-4mM的Ce可将其分别提高50.76%和38.92%;此外,10-3mM La或Ce可分别将胞内可溶性糖含量提高13.83%和34.88%。上述研究表明：在藻类培养基中添加一定浓度的La或Ce,可以加快小球藻细 胞的早期增殖速度,缩短获得最大生物量的培养时间,同时还可提高叶绿素、类胡萝卜素以及可溶性糖的含量,但是两种稀土元素的效应浓度范围略有差异。     

响应面优化提取小球藻油脂及其脂肪酸成分分析

以中性脂为指标对小球藻油脂的提取试剂进行筛选,并运用响应面分析法优化其提取工艺。在单因素实验基础上选取实验因素与水平,根据中心组合实验设计原理,确定小球藻油脂的最佳提取工艺。同时采用气相色谱-质谱联用法对油脂的脂肪酸成分进行定性和定量分析。结果表明小球藻油脂的最佳提取工艺为:提取试剂乙醇正己烷(1∶2),料液比1∶40,超声温度60℃,超声时间52 min,在此条件下提取率达到7.54%。小球藻中饱和脂肪酸、单不饱和脂肪酸和多不饱和脂肪酸的含量分别为51.93%、1.6%和46.47%。并且不饱和脂肪酸主要是中长链脂肪酸(C16-C20),符合生物柴油的理想分子结构。采用响应面法确定的提取条件合理,可用于小球藻油脂的提取。