L-肉碱对眼点拟微绿球藻种群增长及生化组成的影响

【目的】探究L-肉碱对眼点拟微绿球藻(Nannochloropsis oculata)种群增长及生化组成的影响,为L-肉碱对眼点拟微绿球藻营养调控作用和调控机理研究提供参考。【方法】分别采用不同质量浓度(0(对照组),5,50,100 mg/L)的L-肉碱强化培养眼点拟微绿球藻6 d,每组3个重复。每天检测眼点拟微绿球的种群密度,试验结束时收集样品并检测眼点拟微绿球的生化组成。【结果】5 mg/L L-肉碱组眼点拟微绿球的种群密度显著高于其他组(P0.05)。5和50 mg/L L-肉碱组眼点拟微绿球藻总糖含量无显著差异,但均显著高于对照组(P0.05),而显著低于100 mg/L L-肉碱组(P0.05)。5 mg/L L-肉碱组眼点拟微绿球藻的总脂含量显著低于其他3组(P0.05),而其他3组间无显著差异,但以100 mg/L L-肉碱组最高。5 mg/L L-肉碱组眼点拟微绿球藻的可溶性蛋白含量最高,显著高于其他3组(P0.05)。5 mg/L L-肉碱组眼点拟微绿球藻的叶绿素a含量最高,虽与对照组无显著差异(P0.05),但均显著高于50和100 mg/L L-肉碱组(P0.05),而50 mg/L L-肉碱组显著高于100 mg/L L-肉碱组(P0.05)。5和50 mg/L L-肉碱组眼点拟微绿球藻的∑SFA含量显著低于对照组和100 mg/L L-肉碱组(P0.05)。5 mg/L L-肉碱组眼点拟微绿球藻的∑MUFA含量显著高于其他3组(P0.05),其他3组间无显著差异(P0.05)。5和50 mg/L L-肉碱组眼点拟微绿球藻的∑PUFA、∑EPA+DHA和∑n-3含量均显著高于对照组和100 mg/L L-肉碱组(P0.05)。5和100 mg/L L-肉碱组眼点拟微绿球藻的∑n-6含量显著低于对照组和50 mg/L L-肉碱组(P0.05)。【结论】在本试验条件下,添加5 mg/L L-肉碱能显著促进眼点拟微绿球藻的种群增长,提高其可溶性蛋白和总糖含量,并能显著改善其脂肪酸组成。     

Digestibility of the defatted microalgae Nannochloropsis sp. and Desmodesmus sp. when fed to Atlantic salmon,Salmo salar

The aim of the study was to investigate the apparent digestibility coefficient (ADC) of defatted biomass derived from microalgae Nannochloropsis sp. and Desmodesmus sp. when fed to Atlantic salmon postsmolts in seawater. Two experiments, one employing cold‐pelleted and the other employing extruded pellets, were carried out to determine the ADC of dry matter (DM), protein, ash and energy. The test feeds consisted of a fishmeal‐based reference feed and the algal biomass, at a ratio of 70:30, and yttrium oxide as the inert marker. The ADC of DM and protein in fish fed microalgae‐incorporated cold‐pelleted feeds were significantly higher for Nannochloropsis sp. compared with Desmodesmus sp. The Nannochloropsis sp. inclusion in extruded feeds also led to higher ADCs of DM and energy compared with Desmodesmus sp. The extrusion processing significantly increased the ADC of ash in both defatted microalgae biomass, as well as ADCs of DM in Nannochloropsis and protein in Desmodesmus sp. In conclusion, the microalga Nannochloropsis sp. was more digestible than Desmodesmus sp., and extrusion processing can be used as a means to improve digestibility of certain nutrients.     

氮源及浓度对微绿球藻营养价值的影响

以硝酸钠和脲为氮源，分别以1倍及2倍的F／2配方中的氮浓度培养微绿球藻并在培养5d后采收进行营养分析。结果表明：2倍氮浓度组的微绿球藻粗蛋白含量显著高于1倍氮浓度组，相同氮浓度下硝酸钠组比脲组的粗蛋白含量高。氮源及浓度对总脂含量的影响正好与对粗蛋白的影响相反。2倍氮浓度组的微绿球藻氨基酸含量明显高于1倍氮浓度组，相同氮浓度下氮源对氨基酸含量无明显影响。氮源及浓度对微绿球藻脂肪酸中EPA、总饱和脂肪酸、总多不饱和脂肪酸均有极显著影响，氮源相同时高氮浓度组微绿球藻的EPA、∑PUFA含量极显著高于低氮浓度组，相同氮浓度下硝酸钠组极显著高于脲组。     

Distribution of a fish pathogen Listonella anguillarum in the Japanese flounder Paralichthys olivaceus hatchery

The present study was undertaken to investigate the distribution of Listonella anguillarum in a Japanese flounder (Paralichthys olivaceus) hatchery. A total of 2704 isolates were obtained from the developing fish, live diets and artificial feeds of Japanese flounder and their rearing water, 439 of which were identified as L. anguillarum by the combining incubation on thiosulfate-citrate-bile salt-sucrose (TCBS) agar at 35 °C overnight with polymerase chain reaction (PCR) detection for the VAH1 hemolysin gene. L. anguillarum was detected in all seven rotifer samples, with densities of 2.5 × 10³ to 4.6 × 10⁶ colony forming units (CFU) g^− 1. Both the analyzed samples of Nannochloropsis oculata contained this bacterium at densities of 1.6 × 10⁴ to 1.4 × 10⁵ CFU g^− 1. L. anguillarum was detected in only one of four samples of Artemia nauplii with a density of 4.8 × 10⁵ CFU g^− 1 (35%) and it was not detected in the two analyzed artificial feed samples. L. anguillarum was detected in 11 of 18 specimens of larval and juvenile Japanese flounder at densities of 5.0 × 10¹ to 7.4 × 10⁵ CFU g^− 1, while it was not detected in the two analyzed egg specimens of Japanese flounder. These results indicate that L. anguillarum associated with the developing Japanese flounder is likely derived from rearing water and live diets such as rotifers. Further, it is strongly suggested that L. anguillarum is a transient bacterium of the intestinal microflora for the Japanese flounder but is a permanently indigenous one for the Japanese flounder hatcheries.     

几种环境因子对微拟球藻营养物质积累的影响

为探究光强、光质、氮、磷四种环境因子对微拟球藻营养物质积累的影响,设计以下试验:光强试验设置光强梯度为20、80、140和200 μmol photons·m^-2·s^-1;光质试验依照RGB原理,调节红、蓝、绿光比例分别为100%、50%、0%;氮浓度试验设置氮浓度梯度为55.40、13.85、3.46、1.73 mg·L^-1;磷浓度试验设置磷浓度梯度为8.96、2.24、0.56、0.28 mg·L^-1,统一初始接种密度并测定25 d时脂肪酸及色素组成、蛋白及可溶性糖浓度。结果显示,蛋白和可溶性糖浓度随着光强的增大而增大;200 μmol photons·m^-2·s^-1 光强下微拟球藻生长速率最快、生物量最高,且蛋白(5.17 mg·mL^-1)和可溶性糖(2.40 mg·mL^-1) 浓度最大;20 μmol photons·m^-2·s^-1光强下叶绿素a比例最大。光质试验表明,红光对于微拟球藻可溶性糖积累和生长有一定促进作用,其余光质比例对其生长无显著影响,绿光有利于β-胡萝卜素积累,但纯绿光显著抑制蛋白合成。氮浓度为55.40 mg·L^-1时微拟球藻不饱和脂肪酸和二十碳五烯酸占比均达到最大,分别为68.23%和20.50%,且随着氮浓度降低,微拟球藻生长速率、蛋白及还原糖含量均显著降低。同样,随着磷浓度降低,微拟球藻生长速率和蛋白含量均显著下降,磷浓度为2.24 mg·L^-1时更适宜积累可溶性糖。本研究可为微拟球藻在不同环境因子下的营养优化培养提供理论支撑,具有一定的应用意义和经济价值。     

不同营养盐浓度下微绿球藻的生长及水体中氮磷的变化

在单胞藻培养池中 ,以f/ 2为基本培养配方 (其主要成分为NaNO3 74.8mg ,NaH2 PO4 4.4mg ,FeC6H5O7·5H2 O 3.9mg) ,在经消毒的天然河口水中 ,分别添加 1倍、2倍、3倍浓度f/ 2配方的营养盐培养微绿球藻。结果表明 ,添加 2倍营养盐浓度组 ,微绿球藻的生长最快 ,其相对生长常数显著大于添加 1倍营养盐浓度组。在培养过程中 ,水体中NO-3 N、NH+ 4 N、总氮及PO3 -4 P含量下降 ,而NO-2 N含量在培养过程中先降后升。在高浓度营养盐条件下 ,生产单位产量的微绿球藻需要消耗更多的氮肥。     

微绿球藻 (Nannochloropsis oculata培养基的优化

【目的】微绿球藻 (Nannochloropsis oculata) 是一种优良的单细胞饵料微藻,广泛应用于水产养殖。 优化微绿球藻培养基,以期提高其生长速率,降低生产成本。【方法】以宁波大学 3# 配方为基础微藻培养液, 以乙酸钠为碳源,硝酸钾、尿素和氯化铵为氮源,磷酸二氢钾和磷酸二氢钠为磷源,硫酸亚铁和柠檬酸铁为铁源, 通过单因子和正交试验,研究了碳、氮、磷、铁、维生素 B1 （VB1）和 B12（VB12）等主要营养元素对微绿球藻生长、 繁殖的影响。【结果】获得了以天然海水为基础的微绿球藻优化培养基：3 g/L CHCOONa、20 mg/L NH4CL-N、 2 mg/L KH2PO4-P、3 mg/L FeSO4-Fe、0.05 mg/L VB1 和 0.005mg/L VB12;采用优化培养基与宁波大学 3# 培养基对 比培养微绿球藻,结果表明 , 培养 2 ～ 6 d,优化培养基收获微绿球藻的生物量 ( 细胞密度 ) 比宁波大学 3# 培养 基的分别提高了 2.21、2.55、2.30、1.97、1.7 倍;培养 6 d,优化培养基中微绿球藻收获的生物量 ( 细胞密度 ) 达 到 1.74×107 个 /mL, 是宁波大学 3# 培养基的 1.7 倍。【结论】优化培养基极显著地提高了微绿球藻的生物量, 是微绿球藻的良好培养基。     

Detritus accumulation and decomposition in a coastal lake (Acquatina–southern Italy)

• 1. Knowledge about processes and dynamics underlying organic matter accumulation in transitional waters is crucial for the protection of these ecologically important coastal habitats. This study investigated the relationship between large particle accumulation and decomposition in a coastal lake included in a Site of Community Interest (SCI) using sediment trap and litterbag techniques.
• 2. Two sets of sediment traps were deployed at five sites along the longitudinal axis of the lake. One set was emptied once a month for 12 months, and the other twice a year. The contents of the monthly and the 6‐monthly traps and the superficial sediments were then compared to estimate the organic matter accumulation and loss. To determine the mass loss rate of the three major allochthonous sources of detritus (the reed Phragmites australis, the cordgrass Spartina juncea, and the seagrass Posidonia oceanica), litterbags were placed near the sediment traps at three out of the five sites at the beginning of each 6‐month period and retrieved monthly.
• 3. The amount of annual particulate organic matter (POM) deposition in the traps was 1320.2±58.5 g m^?2 y^?1 and consisted of 25% large particles (CPOM). Allochthonous litter comprised an important fraction of CPOM, and its breakdown rate changed with the plant species, site and season. Loss rate of CPOM accumulated at the lake bottom was significantly related with the mass loss rate of reed and cordgrass litter, but not with that of seagrass.
• 4. Due to slow litter breakdown and tidal landward advection, the lake acted as a sediment trap for allochthonous matter, especially from Posidonia. The important role of marine‐derived litter in organic matter sedimentation suggests addressing conservation strategies of the lake functioning towards the selective control of allochthonous CPOM inputs, in particular at the mouth where the incoming tide brings suspended material and salinity decelerates matter flow to the sea and decomposition. This study supports the hypothesis that sedimentation and decomposition dynamics are important factors for coastal lake evolution, and shows litterbag and sediment trap techniques as simple useful investigation tools in management strategies aiming at conserving transitional waters.

Copyright © 2008 John Wiley & Sons, Ltd.     

Overall development of a bioprocess for the outdoor production of Nannochloropsis gaditana for aquaculture

In this paper, a systematic methodology is shown for the scaling‐up of Nannochloropsis gaditana production for aquaculture uses. First, an adequate culture medium was developed, prepared using fertilizers instead of pure chemicals. Subsequently, the performance of N. gaditana was modelled as a function of average irradiance; this model being validated in continuous culture experiments. The model was used to determine the optimal dilution rate as well as the expected biomass concentration and productivity at optimal conditions. Finally, outdoor experiments were performed to confirm the model's validity and to determine optimal conditions at real production step. Biomass productivity values of up to 0.08 g L^?1 day^?1 were obtained at an optimal dilution rate of 0.25 per day in 0.2 m wide flat‐panel reactors using culture medium containing 0.4 g/L NO^?₃ and 0.034 g/L·PO₄^?3. Fish trials with Atlantic Salmon demonstrated that the inclusion of produced biomass into fed increase the final weight up to 5%, thus confirming the adequacy of the biomass produced for aquaculture uses. The growth model and the scaling‐up strategy proposed here are necessary to develop real industrial‐scale processes capable of supplying microalgal biomass to the aquaculture markets, which in turn require a guaranteed supply and quality of the raw materials provided.