辅助能量物质强化环磷酸腺苷发酵合成机制

微生物代谢过程中,环磷酸腺苷(cAMP)由ATP直接环化形成,强化ATP合成有利于产物的积累。在分批发酵24h添加3g/L-broth丙酮酸钠(辅助能量物质),cAMP浓度达到4. 13g/L,比对照批次提高了24. 4%,发酵性能得到明显改善。对关键酶活性及能量代谢水平的测定结果表明,由于丙酮酸钠的添加,丙酮酸激酶的活性显著下降,而6-磷酸葡萄糖脱氢酶、琥珀腺苷酸合成酶和腺苷酸环化酶等产物合成途径中酶的活性均明显提高;异柠檬酸脱氢酶、琥珀酸脱氢酶和呼吸链脱氢酶等酶活性,以及辅因子NADH/NAD+、ATP/AMP均明显提高。表明添加丙酮酸钠改变了糖酵解和磷酸戊糖途径间的碳流分配,使更多碳流向产物合成途径,同时提高了整体能量代谢水平,更利于ATP的生成,为产物的合成提供了物质和能量基础,进而促进了cAMP的合成与积累。     

辅助能量物质强化环磷酸腺苷发酵合成机制 *

微生物代谢过程中,环磷酸腺苷(cAMP)由ATP直接环化形成,强化ATP合成有利于产物的积累。在分批发酵24h添加3g/L-broth丙酮酸钠(辅助能量物质),cAMP浓度达到4.13g/L,比对照批次提高了24.4%,发酵性能得到明显改善。对关键酶活性及能量代谢水平的测定结果表明,由于丙酮酸钠的添加,丙酮酸激酶的活性显著下降,而6-磷酸葡萄糖脱氢酶、琥珀腺苷酸合成酶和腺苷酸环化酶等产物合成途径中酶的活性均明显提高;异柠檬酸脱氢酶、琥珀酸脱氢酶和呼吸链脱氢酶等酶活性,以及辅因子NADH/NAD ⁺、ATP/AMP均明显提高。表明添加丙酮酸钠改变了糖酵解和磷酸戊糖途径间的碳流分配,使更多碳流向产物合成途径,同时提高了整体能量代谢水平,更利于ATP的生成,为产物的合成提供了物质和能量基础,进而促进了cAMP的合成与积累。     

低聚磷酸盐促进cAMP发酵合成的全局转录组分析

目的：以节杆菌Arthrobacter sp. CCTCC 2013431为研究对象,探究低聚磷酸盐作为能量供体促进环磷酸腺苷(cyclic adenosine monophosphate, cAMP)发酵合成的作用机理。方法：在7 L发酵罐中添加低聚磷酸盐,对发酵性能、转录组学、关键酶活性以及重要代谢物水平进行分析,揭示低聚磷酸盐促进cAMP发酵合成的机理。结果：发酵24 h添加2 g/L六偏磷酸钠,cAMP产量显著提高,达到3.64 g/L,与对照组相比提高了33.82%。转录组数据分析表明,由于六偏磷酸钠的添加,227个基因表达量显著上调,265个基因表达量显著下调;磷酸戊糖途径和cAMP合成途径中多数酶编码基因的转录水平,电子传递链中复合体Ⅲ、复合体IV和F₀F₁-ATP酶以及聚磷酸盐激酶编码基因的转录水平,硫氧还蛋白、过氧化氢酶及CLP蛋白酶等编码基因的转录水平均显著提高。此外,对丙酮酸激酶、6-磷酸葡萄糖脱氢酶、腺苷琥珀酸合成酶、腺苷酸环化酶、过氧化氢酶、聚磷酸盐激酶活性以及胞内活性氧、ATP和NADPH等进行测定,进一步证明了转...     

氨茶碱与柠檬酸盐协同作用促进环磷酸腺苷发酵生产

目的:探究通过抑制磷酸二酯酶活性促进cAMP发酵合成的工艺方法.方法:在7 L发酵罐上进行添加氨茶碱的发酵实验,通过对发酵主要参数、关键酶活性、能量代谢水平等进行分析,针对性提出了氨茶碱与柠檬酸盐协同作用促进cAMP合成的发酵工艺.结果:与对照相比,添加5 mg/L氨茶碱批次的cAMP产量提高25.9％,副产物腺苷浓度...     

硫胺素对Arthrobacter sp.A302环磷酸腺苷发酵的影响

研究在培养基中加入硫胺素（V B1）对cAMP发酵的影响。结果表明：V B1的最适添加量为0.5 g/L,与对照组相比,环磷酸腺苷（cAMP）产量和细胞干质量分别提高了36.4%和41.8%,达到7.5和7.8 g/L。琥珀酸和α-酮戊二酸的含量有明显的提高,平均提高了43.59%和40.77%;同时,主要副产物乙酸的含量没有明显变化。在发酵过程中,V B1的加入对ATP的含量及与cAMP合成密切相关的几种酶的活性也有显著的影响。     

氧载体对小白链霉菌发酵生产ε-聚赖氨酸的影响

为了有效改善发酵体系中的溶氧水平,提高小白链霉菌Streptomyces albulus PD-1发酵生产ε-聚赖氨酸的能力,文中通过对氧载体的种类、最佳添加浓度以及添加时间进行筛选,最终确定在0 h添加0.5%(V/V)的正十二烷促进ε-聚赖氨酸生产效果最佳。在5 L发酵罐0 h添加0.5%的正十二烷进行批次补料发酵,ε-聚赖氨酸的产量和菌体干重分别可以达到(30.8±0.46)g/L和(33.8±0.29)g/L,较之对照组分别提高了31.6%和20.7%。ε-聚赖氨酸的产量和菌体干重的提高归因于0.5%正十二烷的添加促进发酵液中溶氧水平从23.8%提高到32%,同时发酵液中的一种主要副产物(聚二氨基丙酸)的含量下降31%。实验结果表明,正十二烷的添加可以提高S.albulus PD-1发酵液中的溶氧水平,抑制副产物的生成,促进ε-聚赖氨酸的合成。     

丙酮酸钠对E．coli CCTCCM208088发酵生产聚唾液酸的影响

研究了丙酮酸钠对E．coliCCTCCM208088发酵生产聚唾液酸的影响。首先在摇瓶水平上优化了丙酮酸钠的添加策略：发酵初始培养基中添加6g／L丙酮酸钠,聚唾液酸的产量达到最高水平3．47g／L,相比空白相比提高了73％,聚唾液酸产率（YP／（x．s））提高了125％。在30L发酵罐中,添加丙酮酸钠使聚唾液酸产量达到了6．6g／L,相对照提高了53．5％。通过有机酸分析,添加丙酮酸钠增强了菌体内三羧酸循环．可能导致胞内能荷水平的提高．从而促进了聚唾液酸的合成。     

化学改性甘蔗渣对固定化细胞发酵产丁醇的影响

旨在研究化学改性的甘蔗渣作为固定化载体对丙酮丁醇梭菌Clostridium acetobutylicum XY16发酵制备生物丁醇的影响。首先利用不同浓度的聚乙烯亚胺(PEI)和1 g/L戊二醛(GA)对甘蔗渣表面进行化学改性,增强甘蔗渣对Clostridium acetobutylicum XY16的附载能力。经4 g/L聚乙烯亚胺和1 g/L戊二醛改性的甘蔗渣(添加量10 g/L)应用到固定化批次发酵中,发酵36 h后丁醇和总溶剂浓度最高,分别达到了12.24 g/L和21.67 g/L,同时溶剂的生产速率达到0.60 g/(L·h),生产速率比游离细胞和未改性甘蔗渣固定化细胞分批发酵分别提高了130.8%和66.7%。在此基础上对改性甘蔗渣固定化的细胞进行6次重复批次发酵,丁醇和总溶剂的产量稳定,溶剂生产速率逐渐提高至0.83 g/(L·h),同时转化率也提高至0.42 g/g。     

代谢途径酶活促进剂对番茄红素发酵的影响

考察了几种代谢途径中关键酶活促进剂对番茄红素发酵的影响。通过添加代谢途径中HMg-CoA还原酶与MVA激酶酶活促进剂,提高类胡萝卜素前体物质的生物合成,从而促进三孢布拉霉菌合成番茄红素的能力。实验结果表明,发酵24 h分别加入质量分数0.05%的某醇及其代谢产物A、1 mg/L的青霉素和质量分数0.1%β-紫罗酮,番茄红素的产量分别提高了31%,32%及35%,最大产量达到1.54 g/L。     

两阶段搅拌转速控制策略发酵生产聚唾液酸

目的:优化聚唾液酸发酵过程的搅拌转速.方法:比较不同搅拌转速对大肠杆菌Escherichia coli K235分批发酵生产聚唾液酸过程的影响.结果:根据发酵前、后期菌体细胞比生长速率和聚唾液酸比合成速率达到最大值所需搅拌转速的不同,提出了两阶段搅拌转速控制策略:发酵前期(0～15h)控制搅拌转速500r/min,发酵中后期控制搅拌转速700r/min.结论:两阶段搅拌转速控制策略使聚唾液酸产量达到3 966mg/L,比恒定搅拌转速500r/min和700r/min分别提高了31.8%和49.3%.将两阶段搅拌转速控制策略与分批补料发酵技术结合,聚唾液酸产量提高到5 108mg/L,山梨醇的转化率达到0.12g/g.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.