Effect of oleic acid on vegetative growth of the aphid-pathogenic fungus Erynia neoaphidis

Abstract The aphid-pathogenic fungus Erynia neophidis grew on a semi-defined medium containing 16 g·1⁻¹ glucose, 3 g·1⁻¹ yeast extract and 5 g·1⁻ mycological peptone only when the medium was supplemented with low concentrations of certain fatty acids. Of these, oleic acid fulfilled the growth requirement at a concentration of 0.02% (v/v), but higher concentrations were toxic, causing complete loss of viability of cultures at a concentration of 0.2% (v/v) in liquid medium and at 4% (v/v) on solid medium. The reduced viability of the fungus in liquid culture compared to that on equivalent solid medium, and at low inoculum density compared to high inoculum density in liquid medium, is explicable in terms of this toxicity.     

海侵地区不同降雨条件下海水灌溉‘油葵G101’的研究

 在对油葵(Helianthus annuus)室内海水砂培试验研究油葵耐海水生物学特征的基础上 ,为获取半干旱海侵区海水大田灌溉的技术参数,以指导当地大田海水灌溉的实际应用,2002（干旱年）、2003年（丰水年）在山东莱州受海水入侵最严重的半干旱地区进行了不同浓度海水补充灌溉‘ 油葵G101’的田间小区试验,着重研究了当地不同雨水条件下在油葵始蕾期、始花期海水灌 溉两水的模式对夏播油葵产量结构及其主要形态指标、植株体内离子分布规律的影响。结果表明 ：1）在当地的土壤条件下,无论是干旱年份（2002年）,还是丰水年份（2003年）,在油葵生长期内（约100 d）,补充灌溉两水,40%比例的海水灌溉是夏播油葵保证一定经济产量的安全指标,在干旱年份,海水比例超过40%时,油葵籽产量即显著下降,而在丰水年份,即使用60%比例的海水灌溉,油葵籽产量与40%处理也无显著差异。综合考虑油葵经济产量、节省 淡水用量等因素,40%海水补充灌溉两水可视为该海侵地区灌溉油葵适宜的海水补充灌溉额度。2）干旱年份,20%海水灌溉处理下,初花期油葵除茎秆直径和葵盘鲜重外,其它各生理 生态指标与淡水灌溉处理无显著性差异(p=0.05)。而在丰水年份,即使用40% 的海水灌溉, ‘油葵G101’主要形态指标与淡水灌溉也无显著差异。3）0～40%比例海水灌溉处理, 夏播油葵叶片能保持相对较高的Ca2+、Mg2+含量,而根系吸收的K+向葵盘的选择性运输能力很强。Na+主要积累在根部、茎部,而叶和葵盘中含量较低。Cl－在茎中含量最高。     

Production of lipase by high cell density fed-batch culture of Candida cylindracea

Candida cylindracea NRRL Y-17506 was grown to produce extracellular lipase from oleic acid as a carbon source. Through flask cultures, it was found that the optimum initial oleic acid concentration for cell growth was 20 g l⁻¹. However, high initial concentrations of oleic acid up to 50 g l⁻¹ were not inhibitory. The highest extracellular lipase activity obtained in flask culture was 3.0 U ml⁻¹ after 48 h with 5 g l⁻¹ of initial oleic acid concentration. Fed-batch cultures (intermittent and stepwise feeding) were carried out to improve cell concentration and lipase activity. For the intermittent feeding fed-batch culture, the final cell concentration was 52 g l⁻¹ and the extracellular lipase activity was 6.3 U ml⁻¹ at 138.5 h. Stepwise feeding fed-batch cultures were carried out to simulate an exponential feeding and to investigate the effects of specific growth rate (0.02, 0.04 and 0.08 h⁻¹) on cell growth and lipase production. The highest final cell concentration obtained was 90 g l⁻¹ when the set point of specific growth rate (μ_set) was 0.02 h⁻¹. High specific growth rate (0.04 and 0.08 h⁻¹) decreased extracellular lipase production in the later part of fed-batch cultures due to build-up of the oleic acid oversupplied. The highest extracellular lipase activity was 23.7 U ml⁻¹ when μ_set was 0.02 h⁻¹, while the highest lipase productivity was 0.31 U ml⁻¹ h⁻¹ at μ_set of 0.08 h⁻¹.     

Effect of several factors on soluble lipase-mediated biodiesel preparation in the biphasic aqueous-oil systems

Biodiesel is increasingly perceived as an important component of solutions to the important current issues of fossil fuel shortages and environmental pollution. Utilization of soluble lipase offers an alternative approach to lipase-catalyzed biodiesel production using immobilized enzyme or whole-cell catalysis. Soluble lipase NS81020, produced by submerged fermentation of genetically modified Aspergillus oryzae microorganism, was first proposed here as the catalyst of biodiesel preparation with oleic acid in the biphasic aqueous-oil systems. The effect factors such as enzyme concentration, water content, temperature, molar ratio of methanol to oil, stirring rate and pH of buffer solution on the esterification rate were investigated systematically. The reaction time could be shortened with the increasing of enzyme concentration as long as the maximum enzyme absorptive capacity on the interface in the biphasic aqueous-oil systems was not achieved. The optimal water content in the biphasic aqueous-oil systems was 10 wt% by oleic acid weight. The reaction rate was enhanced with the increasing molar ratio of methanol to oil, the increasing stirring rate or the decreasing temperature. Although soluble lipase NS81020 had lower activity at pH 10.55, hydroxyl ion conduced to restrain hydrolysis of methyl ester and facilitated the reaction toward the methyl ester formation.     

Oleic acid delays and modulates the transition from respiratory to fermentative metabolism in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> after exposure to glucose excess

This work aimed to study the transition from respiratory to fermentative metabolism in Saccharomyces cerevisiae CEN.PK 113-7D and more specifically to evaluate the implication of the acetyl-coenzymeA-derived carbon transport from cytosol to mitochondria in the onset of the metabolic shift. The strategy consisted in introducing, during aerobic glucose-limited chemostat (D = 0.16 h¹), a local perturbation around the step to be studied by the addition of cosubstrate and in analyzing the consequences of such a perturbation on the metabolic transition. Oleic acid and l-carnitine were among the tested cosubstrates because they were known to stimulate enzymes implicated in the acetyl-coenzymeA transport between the different cell compartments, such as the carnitine acetyl transferases. The metabolic transition was then comparatively quantified in sole glucose and in glucose/oleic acid chemostats in presence/absence of l-carnitine after a pulse of glucose. Feeding the culture with oleic acid (D _ole = 0.0041 and 0.0073 h¹) led to a delay in the onset of the metabolic shift (up to 15 min), a 33% decrease in the ethanol production and a redirection of the carbon flux toward biomass production. The data clearly showed a modulation of the carbon distribution among respiration and fermentation, in favor of a decrease in the “short-term” Crabtree effect by the oleic acid. David Feria-Gervasio and Jean-Roch Mouret worked equally on this project and should be considered both as first authors. An erratum to this article can be found at     

Anti-plasticization of cassava starch by complexing fatty acids

The effect of adding 1–8% amylose complexing fatty acids (CFA), such as linoleic and oleic acids, on the glass transition temperature (T_g) of cassava starch (CS) with moisture content varying from 5 to 35% (dry basis) was studied. The main relaxation temperature (T_α), associated with the glass transition temperature of the samples (T_g), was determined by dynamic-mechanical-thermal analysis. The plasticizing behavior of water in the blends was evidenced by a decrease of T_α values with moisture content. The effect of CFA on CS was found to be a function of moisture content. At low moisture (<11%) it caused an anti-plasticization effect, while at higher moisture contents it produced plasticization. The anti-plasticizing effect of CFA on CS was attributed to amylose–lipid complex formation.     

不同类型高脂状态对肝细胞内SIRT1表达的调节

目的:肥胖是2型糖尿病的高危因素,但脂代谢异常引起胰岛素抵抗的分子机制仍需探讨.去乙酰化酶SIRT1在细胞内的糖脂代谢过程中起着重要的作用,本文应用体内外模型探讨不同类型高脂状态下肝细胞内SIRT1蛋白表达的改变,进而揭示肥胖引起2型糖尿病发病的可能分子途径.方法:分别采用含有不同浓度棕榈酸或油酸的培养液培养HepG2肝细胞1天,检测细胞内SIRT1的蛋白水平;同时采用高脂饲料造小鼠肥胖模型,检测肝脏组织内SIRT1的表达改变.结果:三种不同浓度的棕榈酸均未引起HepG2肝细胞内SIRT1表达的改变,与棕榈酸有所不同,两种浓度的油酸均引起细胞内SIRT1表达的显著降低,分别是对照组的65％和58％.在高脂动物模型中同样未发现肝组织内SIRT1蛋白表达的改变.结论:SIRT1作为细胞内糖脂代谢通路的交叉点,其表达的改变有利于揭示脂代谢异常是如何引起糖代谢紊乱的.油酸的大量摄入可以导致甘油三酯在肝脏中的蓄积和影响肝细胞的胰岛素敏感性,而本文提示油酸诱导的细胞代谢改变很可能通过下调SIRT1来实现,其表达的改变为探讨肥胖引起2型糖尿病的分子机制提供线索.     

油酸诱导小型猪肺水肿模型的建立

目的制备油酸诱导小型猪肺水肿的动物模型,便于进行肺水肿的发病机制和相关治疗的研究。方法家养小型猪20只麻醉后随机分A、B两组,A组（n=10）为对照组,B组（n=10）为油酸组（油酸0.15 mL/kg经动物耳缘静脉缓慢注射）,观察两组动物肺组织病理改变、计算肺含水量及肺湿干重比。结果B组动物注射油酸后肺部出现明显的肺水肿病理改变,肺湿/干重比及肺含水量的值明显高于A组（P〈0.05）。结论本实验成功复制油酸诱导小型猪肺水肿动物模型,其病理组织切片符合肺水肿的典型病变。