自养黄杆菌合成羟基丁酸和羟基戊酸共聚体的发酵研究

采用本实验室从土壤中分离到的一株自养黄杆菌进行了羟基丁酸和羟基戊酸共聚体〔P(HB-co-HV)〕的发酵试验。实验结果表明,该菌株是自养黄杆菌葡萄糖运输突变株,可以葡萄糖、果糖、蔗糖、麦芽糖、乙酸盐、乳酸盐和苹果酸盐作为唯一碳源,尤以葡萄糖和果糖效果最佳。硫酸铵、氯化铵和蛋白胨等不同氮源不影响其生长,却影响细胞中P(HB-co-HV)的含量和P(HB-co-HV)中HV/HB的比例。应用两阶段控制方式,经42h的补料分批发酵,细胞浓度达34.9g·L~(-1),P(HB-co-HV)浓度达25.28g·L~(-1)。细胞和P(HB-co-HV)生产速率系数分别为0.83g·L~(-1)”·h~(-1)和0.61g·L~(-1)·h~(-1)。以基质为基准的细胞得率系数(Yx/s)、产物得率系数(Yp/s)和以干细胞为基准的产物得率系数(Yp/x)分别为0.283(g/g)、0.174(g/g)和0.73(g/g)。改变培养基中碳氮源组分可将P(HB-co-HV)中HB的含量调节在24％～78％之间。     

苏云金芽孢杆菌BMB005的代谢动力学

建立了苏云金芽孢杆菌BMB005的代谢动力学模型,成功地模拟了该菌株的生长、葡萄糖、聚-β-羟丁酸(PHB)、吡啶二羧酸(DPA)和毒蛋白(ICPs)变化过程,得到了菌体最大比生长速率、菌体对葡萄糖的得率系数、PHB对葡萄糖的得率系数、DPA和晶体蛋白的最大比生成速率以及DPA和晶体蛋白对PHB的得率系数等一系列重要动力学参数,为优化苏云金芽孢杆菌BMB005的发酵过程提供了基础。     

重组巴氏毕赤酵母恒化培养动力学及代谢迁移特性研究

通过对甲醇营养型毕赤酵母基因工程菌以碳源甘油为限制性基质进行恒化培养动力学试验 ,结果认为 :(1 )细胞光密度与其干、湿重呈线性关系 ,当细胞光密度 (OD60 0 )为 1 0 0时细胞湿重 (WCW)为 1 2 8 3g L ,细胞干重 (WDW)则为 2 2 9g L ;(2 )基因工程菌P .pastoris的生长与限制性基质甘油残留浓度的关系符合Monod关系式 ,通过 1 μ对 1 S进行线性回归得 μmax=0 .366h- 1,Ks=0 .1 82 3g L ,经参数推导甘油最大菌体得率系数YG =0 .54g g ,菌体维持生长消耗底物系数m =0 .0 0 69g (g·h) ;氧最大菌体系数YX O2 =30 .96g moL ,菌体维持生长时消耗氧系数mO2 =0 .0 0 0 8mol (g·h) ,最适理论稀释速率Dm =0 .341h- 1;(3)从氨水的消耗速率和呼吸商 (RQ)的变化认为随着比生长速率 (μ)的增大 ,甘油代谢流从糖原异生和磷酸戊糖途径线性地向糖酵解和三羧酸循环途径进行代谢迁移 ,即糖酵解和三羧酸循环途径的代谢流量在线性地增大     

L－精氮氨发酵动力学特性的分析研究

在2．6L自控小罐上用突变株971．1进行了L－精氨酸分批发酵,对涉及细胞群体代谢速率和代谢效率的发酵动力学行为进行了分析研究,内容有：(1)分析了该发酵过程的动力学类型,并提出了定量分类的“生长比速率双相比较法”;(2)在实验基础上组建了L－精氨酸发酵的数学模型,(3)通过对不同溶氧系数kLa条件下的菌体生长耗底物分数αx,、产物生成耗底物分数αp的分析比较,讨论了氧的供给对底物转化成L-精氨酸效率的影响。     

不同碳源对大肠杆菌lpdA突变菌累积丙酮酸的影响

为了利用大肠杆菌构建模式"细胞工厂",必须了解在构建过程中各种因素的影响。本研究选用敲除了lpdA基因的大肠杆菌作为模型细胞,考察了该突变菌在合成培养基中利用葡萄糖、果糖、木糖和甘露糖累积丙酮酸的能力。结果显示,在初始糖浓度为10g/L的情况下,lpdA突变菌可以很好地利用葡萄糖、果糖、木糖和甘露糖转化丙酮酸,其得率分别达到了0.884g/g、0.802g/g、0.817g/g和0.808g/g,且在以葡萄糖、果糖和木糖发酵时,丙酮酸的积累过程与细胞生长偶联。甘露糖发酵的情况则不同:菌浓度很快达到平台期,随后丙酮酸积累和甘露糖消耗都表现为线性变化。当在考察了不同的接种量对lpdA突变菌发酵葡萄糖的影响时发现,大接种量能加快葡萄糖消耗速率、丙酮酸的积累速率和细胞生长速率,但丙酮酸得率却明显下降。这些结果对构建以大肠杆菌为母体的模式"细胞工厂"有参考价值。     

金龟子绿僵菌IMI330189液体发酵动力学研究

研究了金龟子绿僵菌IMI330189的液体发酵动力学。利用Sigmoid函数构建了该菌株液体发酵过程中的菌体生长和底物消耗的动力学模型,并运用Origin7.5软件拟合求解出各模型参数。结果表明,模型能够较好地拟合绿僵菌IMI330189液体发酵过程,其比生长速率在发酵第22.8h达到最大值,为0.084h-1;总糖比消耗速率在第9.6h达到最大值,为0.246h-1;总氮比消耗速率在第10.3h达到最大值,为0.007h-1;菌体对总糖的得率系数在39.8h达到最高,为0.861g/g。模型拟合和实验数据具有良好的适应性,基本反映了绿僵菌IMI330189液体发酵过程的动力学特征,为其液体发酵工艺的优化和发展奠定了基础。     

灵芝胞外多糖分批发酵动力学模型

利用分批发酵研究了灵芝(Ganoderma lucidum)胞外多糖的合成特性,结果表明Ganodermalucidum多糖合成和菌体生长呈部分生长关联型。菌体干重、胞外多糖分别达到15.56g·L-1、3.02g·L-1,胞外多糖对细胞干重得率系数(Yp/x)为0.19。根据分批发酵试验结果采用Logistic方程、Luedeking-Piret方程和类似Luedeking-Piret方程,得到了描述灵芝生长、胞外多糖以及葡萄糖底物消耗分批发酵动力学模型。同时在初始葡萄糖变化较大范围内,试验数据与模型预测值进行了比较拟合,平均相对误差小于5%,表现出很好的适用性。表明该动力学模型对指导灵芝胞外多糖的发酵生产具有实际意义。     

法夫酵母分批发酵虾青素动力学研究

通过三联30L全自动发酵罐对虾青素产生菌法夫酵母的分批发酵动力学进行了研究,结果表明,法夫酵母的生长与限制性基质葡萄糖浓度之间符合Logistic方程,建立了细胞生长、产物合成和基质消耗随时间变化的数学模型。应用MATLAB软件对发酵动力学模型进行最优参数估计和非线性拟和,获得最大比生长速率（umax）和产物得率（Yp/x）分别为0.1829/h、0.1524g/g,虾青素分批发酵中细胞生长与产物合成属于偶联型,模型模拟计算结果和实验值能较好地吻合,动力学研究结果表明该模型能较好地反映细胞的生长、底物消耗和产物合成过程机制。     

通气量对灵芝菌丝体液态深层发酵合成灵芝三萜的影响

采用5 L搅拌式发酵罐研究灵芝菌丝体液态深层发酵合成灵芝三萜的扩大培养条件,考察了不同条件下的通气量对灵芝菌丝体生长、比生长速率、灵芝三萜合成、比合成速率、还原糖消耗、还原糖比消耗速率、铵根离子消耗以及铵根离子比消耗速率的影响。研究结果表明,通气量能够显著影响菌丝体的生长以及灵芝三萜的合成,当通气量为8 L/min时,菌丝体合成灵芝三萜得率和生产强度最高,分别为0.204 g/L和0.00131 g/(L·h),最大菌丝体得率达到8.77 g/L。发酵过程中菌丝体最大比生长速率为0.0704 1/h,灵芝三萜最大比合成速率为0.0256 1/h,还原糖和铵根离子最大比消耗速率分别为0.562 1/h和0.0171 1/h。     

蛹虫草液体培养条件的优化及生长动力学考察

为了优化蛹虫草菌的液体培养条件 ,对液体培养菌丝的生长情况进行了研究。采用摇瓶培养的方法 ,以发酵得率为指标确定培养条件。结果表明 :优化培养基成分确定为蛋白胨 1.5 % ,葡萄糖 2 % ,KH2 PO4 0 .15 % ,Mg SO40 .0 5 %、VB1 5 m g/ L .2 ,4 - D 2 mg/ L .该培养基下发酵得率达 1.4～ 2 .2 g/ 10 0 m L ;考察了蛹虫草菌液体培养的外部条件 ,确定为 :装料系数为 30 % ,培养基 p H为 5 .5 ,接种量为 0 .0 3g,摇床振荡频率为 12 0 r· m in- 1 ;利用优化培养基得到了生长代谢曲线。在相同条件下 ,优化培养基比原来培养基的发酵得率提高了 4 .5 % ,研究初步得到蛹虫草菌液体培养条件和生长动力学 ,为工业化生产提供了一定的依据     

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.