碳和氮代谢被抑制诱导雨生红球藻细胞内虾青素的合成

为研究雨生红球藻(Haematococcus pluvialis)合成虾青素的机理,文中分析了不同诱导条件下藻细胞内氮和碳代谢的变化。结果表明:强光照(HL)、添加乙酸钠(AA)、缺氮(NF)和缺磷(PF)都直接或间接地影响了雨生红球藻细胞内1,5-二磷酸核酮糖羧化酶(Rub isco)和硝酸还原酶(NR)的活性,导致2种酶的活性大幅度下降。只有当Rub isco和NR的活性降到非常低的水平时,藻细胞才开始合成虾青素。与此相反,对照(CK)中这2种酶的活性一直较高,但细胞内没有虾青素积累。由于Rub isco和NR是雨生红球藻碳代谢和氮代谢的关键酶,因此碳和氮代谢被抑制是诱导雨生红球藻合成虾青素的原因。     

强光照对雨生红球藻合成虾青素的影响

在不同的光照强度下研究了雨生红球藻细胞内虾青素的合成与初级代谢的关系.在强光(HL)和中等强度(ML)的光照条件下,雨生红球藻细胞内1,5-二磷酸核酮糖羧化酶 (Rubisco)和硝酸还原酶(NR)的活性第1天大幅度提高,2天后又迅速下降.与此同时,硝酸盐浓度也快速降低.当虾青素在第4天(HL)和第6天(ML)开始合成时, HL中Rubisco和NR活性以及NO3-浓度分别下降了75.5%,71.5% 和96.2%,而ML中则下降了76.5%,74.7% 和94.3%.相比之下,在低光照(LL)条件下,实验结束时三个指标仅下降了25.9%,29.8% 和56.8%,细胞中没有虾青素积累.结果表明强光提高了Rubisco 和 NR活性,导致硝酸盐浓度迅速降低而最终又抑制了这两种酶的活性,造成雨生红球藻光合作用效率下降即"碳饥饿".在此状态下,为了生存,细胞内合成虾青素的相关基因被激活,藻细胞开始合成并积累虾青素.     

从雨生红球藻藻泥中选择性提取虾青素

以雨生红球藻湿藻泥为原料,研究了不同有机溶剂对胞内油脂和虾青素选择性提取分离的影响,通过酸解破壁提高虾青素和油脂的提取效率。结果表明,连续乙醇提取可对胞内色素和油脂有效分级提取,先提取出极性组分(叶绿素和极性脂),再提取中性组分(类胡萝卜素和中性脂)。中等极性溶剂或溶剂体系对类胡萝卜素的选择性和提取率较好;乙醇/乙酸乙酯混合溶剂提取类胡萝卜素的总得率(干重)达25.31 mg/g,提取率为69.35%。对雨生红球藻湿细胞进行酸解破壁处理有助于提高虾青素和油脂的提取率。在最优酸解破壁条件(盐酸浓度1 mol/L,温度60℃,时间60 min)下,含水80%的雨生红球藻藻泥的油脂总得率(干重)达418 mg/g,总脂提取率达97%。     

雨生红球藻合成虾青素过程中分泌铵离子的研究

雨生红球藻在在缺氮(NF)的条件下,随着虾青素的合成,肽链内切酶(EP)的活性上升而蛋白质含量下降,天冬酰氨酸含量在前4天增加然后又减少,铵离子浓度则持续上升。相比之下,在氮充足(NR)的培养液中,藻细胞不合成虾青素,蛋白质和天冬酰氨酸的含量以及EP的活性基本稳定,培养液中也没有检测到铵离子。上述结果表明:①降解的蛋白质为虾青素的合成提供了碳源,②EP参与了蛋白质的降解反应,③为避免铵离子的毒害作用,蛋白质降解所产生的部分氨临时贮存在天冬酰氨酸中,而其余的则分泌到细胞外。     

雨生红球藻的新繁殖方式及其藻蓝蛋白的合成

雨生红球藻(Haematococcus pluvialis)是一种能够合成强抗氧化剂-虾青素的单细胞绿藻,然而由于其生长速率缓慢,制约了虾青素产量的提高。在对雨生红球藻细胞周期的研究中,首次发现了雨生红球藻在高温和低光照条件下的一种特殊繁殖方式,该繁殖方式比已知的营养繁殖和无性繁殖速度快。繁殖过程中厚壁孢子萌发产生大量的小细胞,并且这些小细胞中含有以前在绿藻中从未发现的捕光色素蛋白—藻蓝蛋白(最大吸收波长λmax=621 nm,最大荧光发射波长λmFax=643 nm)。这一发现对于提高天然虾青素的产量和藻蓝蛋白的生产以及藻类的进化有着重要的意义。     

转光膜在雨生红球藻养殖上的应用

通过对雨生红球藻在不同光质条件下生长的比较,确定了红色光有利于藻生长,进而用2.5 L气升式光照反应器在转光膜及普通PE膜下培养藻进行对比,结果显示雨生红球藻生物量、色素、光合活性等几项生物指标在转光膜条件下明显高于普通PE膜. 在气升式反应器内培养的藻细胞,接种9 d,虾青素含量可达3.57 mg/L,叶绿素浓度达到12.42 mg/L,干重提高8.8%以上.     

雨生红球藻合成虾青素过程中分泌铵离子

The present study is focused on protein degradation during astaxanthin synthesis in Haematococcus plu- vialis under high irradiance and nitrogen deficient conditions. It was found that with the onset of astaxanthin synthesis in the cultures of high light and nitrogen-free （HF）, high light and nitrogen-repletion （HR）, and low light and nitrogen-free （LF）, （1） endopeptidase （EP） activities increased along with decrease in protein content, （2） asparagine in HF and HR rose significantly before the first 4 and 5 day, but fell after that time. While, it increased slowly and continuously in LF, （3） ammonium increased continuously in HF and HR, whereas in LF, it was detected on the sixth day, and increased slowly on the following days. By contrast, in low light and nitrogen-repletion culture, （LR）, the contents of protein and asparagine as well as EP activity were maintained relatively constant, no astaxanthin and ammonium were detected. Furthermore, when HF was sealed and bubbled with CO2-free gas （02 and N2）, astaxan- thin content increased as the protein level decreased. These results strongly suggest that （1） the degraded protein served as a substitutive carbon source, to some extent, for the biosynthesis of astaxanthin, （2） endopeptidase was involved in the degradative process, （3） for detoxification, part of the ammonium generated by protein degradation was transiently stored in asparagine, whereas the rest of it was expelled into the culture broth.     

超声辅助提取虾青素的工艺优化及动力学研究

以乙醇为溶剂,采用超声辅助方法从新鲜雨生红球藻中提取虾青素,优化工艺参数。首先采用单因素方法研究提取时间、超声功率、料液比对提取得率的影响,然后通过响应面方法优化工艺参数。结果表明提取时间28 min,超声功率87 W,料液比1∶25时,虾青素得率最高,达到(35.93±0.37)mg/g。该最佳条件下的虾青素提取符合二级动力学规律(R²=0.998 9),提取速率与浓度差的平方成正比。该方法制备的虾青素提取液对DPPH和OH的半抑制浓度分别为(16.14±1.58)μg/mL和(0.93±0.18)μg/mL。     

虾青素来自天然的超级抗氧化剂

<正>随着信息化的快速普及,人们对新事物的了解愈加即时,久而久之,人们面对大量的碎片化信息可能只会一扫而过,对其内含"究竟"却知之甚少,缺乏了对事物本身的深入了解。本篇文章就带领大家了解耳熟未必能详的虾青素。     

Concomitant NH_4~+ Secretion During Astaxanthin Synthesis in Haematococcus pluvialis Under High Irradiance and Nitrogen Defi-cient Conditions

The present study is focused on protein degradation during astaxanthin synthesis in Haematococcus plu- vialis under high irradiance and nitrogen deficient conditions. It was found that with the onset of astaxanthin syn-thesis in the cultures of high light and nitrogen-free (HF), high light and nitrogen-repletion (HR), and low light and nitrogen-free (LF), (1) endopeptidase (EP) activities increased along with decrease in protein content, (2) aspar-agine in HF and HR rose significantly before the first 4 and 5 day, but fell after that time. While, it increased slowly and continuously in LF, (3) ammonium increased continuously in HF and HR, whereas in LF, it was detected on the sixth day, and increased slowly on the following days. By contrast, in low light and nitrogen-repletion culture, (LR), the contents of protein and asparagine as well as EP activity were maintained relatively constant, no astaxanthin and ammonium were detected. Furthermore, when HF was sealed and bubbled with CO2-free gas (O2 and N2), astaxan-thin content increased as the protein level decreased. These results strongly suggest that (1) the degraded protein served as a substitutive carbon source, to some extent, for the biosynthesis of astaxanthin, (2) endopeptidase was involved in the degradative process, (3) for detoxification, part of the ammonium generated by protein degradation was transiently stored in asparagine, whereas the rest of it was expelled into the culture broth.     

3,5-双三氟甲基苯甲酸的合成研究

3,5-双三氟甲基苯甲酸[CAS:725-89-3]的合成是先通过1,3-二溴-5,5-二甲基乙内酰脲,与1,3-双三氟甲基苯生成3,5-双三氟甲基溴苯,收率98%,选择性99%.然后由3,5-双三氟甲基溴苯作原料来合成3,5-双三氟甲基苯甲酸,收率72%以上.本文讨论了不同反应摩尔比,反应温度等条件,并得到最优化条件.