Enhancement of butanol production and reducing power using a two-stage controlled-pH strategy in batch culture of Clostridium acetobutylicum XY16

The effects of pH control on the process of acetone/butanol/ethanol (ABE) production in batch cultures of Clostridium acetobutylicum XY16 have been investigated. Based on the specific acid- and solvent-forming rates in batch fermentation at different pH values (from 4.3 to 6.0), a two-stage controlled-pH strategy was developed in which the pH was shifted from 5.5 to 4.9 after a dry cell weight of 0.5 g L(-1) was achieved. By applying this strategy, the maximum ABE concentration and productivity reached 20.3 g L(-1) and 0.63 g L(-1) h (-1), and were significantly improved by 12.2 and 40.1 %, respectively, compared with the process with no pH control. In addition, reducing power capability was significantly enhanced by this strategy. The two-stage controlled-pH strategy was a convenient and rapid method for high intensity ABE production.     

逆境相关植物锌指蛋白的研究进展

锌是植物必需的营养元素,锌指蛋白因其具有指状结构特征且能结合Zn2 而得名,植物锌指蛋白包含特有的QALGGH保守结构,可能涉及调控植物特有的生物学功能。人们已经从拟南芥(Arabidopsis thaliana)、矮牵牛(Petunia hybrida Vilm)、水稻(Oryza sativa)、大豆(Glycine max)、棉花(Gossypium hirsutum)等植物中克隆了许多编码锌指蛋白的基因,并对其结构及功能进行了研究。利用转基因技术,将一些与逆境胁迫相关的锌指蛋白基因在目标植物中过量表达后,能对植物起到增强抗逆性的作用,说明锌指蛋白在增强植物逆境抗性方面有着广阔的应用前景。     

用SARS冠状病毒全基因组芯片杂交方法分析SARS-CoV

为从临床样品中检测和分析SARSCoV病毒打基础,并为分析SARSCoV病毒的复制和转录等机理提供一种有效方法。以SARS冠状病毒TOR2株序列作为标准设计和制备一种覆盖SARS冠状病毒全基因组的寡聚核苷酸芯片,探针长度为70nt,每相邻的探针序列重复25nt,共660条。用该芯片分析了细胞培养的SARSCoV病毒总RNA、7个SARSCoV病毒的基因克隆片段。对RNA样品用随机引物进行反转录PCR获得cDNA。对DNA用随机引物扩增和dUTPcy3标记。结果用这种芯片杂交检测SARSCoV病毒RNA可见阳性信号呈全基因组分布,并且有多处连续的阳性信号点;用正常人的白细胞RNA为对照,杂交未出现明显阳性信号。检测7个SARSCoV病毒基因克隆片段,在该片段相应的探针区段出现连续阳性信号点。这种方法可有效地检测和分析样品中SARS冠状病毒全基因组的信息。     

连作杨树人工林细根寿命的代际差异及其影响因素

细根寿命是调控森林生产力形成的关键。通过在连作Ⅰ、Ⅱ代杨树人工林固定样地内埋设微根管,对杨树不同根序细根年度生长动态开展连续观测并进行生存分析。结果表明,杨树不同根序细根累积生存率存在显著差异,高级根(3—5级)寿命较长,其累积生存率显著高于1级和2级细根。杨树细根寿命存在显著的代际差异,连作Ⅱ代人工林活根量、死根量和细根总量均高于Ⅰ代林。连作Ⅱ代人工林细根中位值寿命为(90±16)d,显著低于Ⅰ代人工林((102±22)d)。连作Ⅱ代林各根序细根数量、分布比例均高于Ⅰ代林,低级细根累积生存率低于Ⅰ代林而高级细根累积生存率显著高于Ⅰ代林。连作杨树人工林细根寿命显著受制于土壤环境,1级细根寿命与土壤速效氮相关性极显著(r=-0.861),2级细根寿命与土壤物理性状相关性较强且与土壤酚酸含量呈现极显著相关(r=0.870),高级根序细根寿命与土壤物理性质和养分状况等也具有一定相关性。连作杨树人工林土壤酚酸累积和养分有效性下降影响了细根寿命和周转,并进而造成净初级生产力损耗,相关结论为连作杨树人工林生产力衰退机理模型的建立提供了科学依据。     

Engineering of Plasmin-Resistant Forms of Streptokinase and Their Production in Bacillus subtilis: Streptokinase with Longer Functional Half-Life

The short in vivo half-life of streptokinase limits its efficacy as an efficient blood clot-dissolving agent. During the clot-dissolving process, streptokinase is processed to smaller intermediates by plasmin. Two of the major processing sites are Lys59 and Lys386. We engineered two versions of streptokinase with either one of the lysine residues changed to glutamine and a third version with both mutations. These mutant streptokinase proteins (muteins) were produced by secretion with the protease-deficient Bacillus subtilis WB600 as the host. The purified muteins retained comparable kinetics parameters in plasminogen activation and showed different degrees of resistance to plasmin depending on the nature of the mutation. Muteins with double mutations had half-lives that were extended 21-fold when assayed in a 1:1 molar ratio with plasminogen in vitro and showed better plasminogen activation activity with time in the radial caseinolysis assay. This study indicates that plasmin-mediated processing leads to the inactivation of streptokinase and is not required to convert streptokinase to its active form. Plasmin-resistant forms of streptokinase can be engineered without affecting their activity, and blockage of the N-terminal cleavage site is essential to generate engineered streptokinase with a longer in vitro functional half-life.     

Biochemical and immunological studies of nucleocapsid proteins of severe acute respiratory syndrome and 229E human coronaviruses

Severe acute respiratory syndrome (SARS) is a serious health threat and its early diagnosis is important for infection control and potential treatment of the disease. Diagnostic tools require rapid and accurate methods, of which a capture ELISA method may be useful. Toward this goal, we have prepared and characterized soluble full-length nucleocapsid proteins (N protein) from SARS and 229E human coronaviruses. N proteins form oligomers, mostly as dimers at low concentration. These two N proteins degrade rapidly upon storage and the major degraded N protein is the C-terminal fragment of amino acid (aa) 169-422. Taken together with other data, we suggest that N protein is a two-domain protein, with the N-terminal aa 50-150 as the RNA-binding domain and the C-terminal aa 169-422 as the dimerization domain. Polyclonal antibodies against the SARS N protein have been produced and the strong binding sites of the anti-nucleocapsid protein (NP) antibodies produced were mapped to aa 1-20, aa 150-170 and aa 390-410. These sites are generally consistent with those mapped by sera obtained from SARS patients. The SARS anti-NP antibody was able to clearly detect SARS virus grown in Vero E6 cells and did not cross-react with the NP from the human coronavirus 229E. We have predicted several antigenic sites (15-20 amino acids) of S, M and N proteins and produced antibodies against those peptides, some of which could be recognized by sera obtained from SARS patients. Antibodies against the NP peptides could detect the cognate N protein clearly. Further refinement of these antibodies, particularly large-scale production of monoclonal antibodies, could lead to the development of useful diagnostic kits for diseases associated with SARS and other human coronaviruses.     

常用食品防腐剂抗菌作用的研究

采用杯碟法和琼脂平板点种法分别测定２０种常用食品防腐剂对３０株菌的抑菌圈直径和最低抑菌浓度,借此判断药剂抗菌力的大小。实验结果表明,在所测２０种防腐剂中,对细菌抑制力最强者是乙酸,对霉菌和酵母菌抑制力最强者是富马酸二甲酯。     

葡激酶的研究进展

本文综述了葡激酶的生化特性、溶栓特性、免疫原性和临床应用方面的研究进展。