正交试验法探讨单酸降解纤维素的最佳条件

正交试验法探讨了乙酸、草酸、盐酸、硫酸等单酸降解植物纤维素的最佳条件。研究结果表明,乙酸降解纤维素时,影响因素的主次顺序为：A＞B＞C,最佳组合为A3B1C2。即乙酸浓度为30％,温度40℃,反应1．5h为最佳条件,验证性试验结果表明,单用乙醇能使纤维素降解成葡萄糖的转化率达42．2％。而草酸影响因素的主次则为A＞C＞B,最佳组合为A2C1B2。即草酸度浓度0％,70℃酸解1h为最佳条件。在此条件下,转化率可达40．8％。对于盐酸影响因素的主次为A＞B＞C,最佳组合为A3B3C1。即在20％盐酸,100℃酸解1h的条件下,转化率可达42．8％。而硫酸影响因素的主次顺序为B＞A＞C,最佳组合为A3B3C1。即在40％硫酸,100℃反应1h的最佳条件下能使转化率达40．9％。研究还发现,乙酸、草酸、盐酸、硫酸降解纤维素特性不同。乙酸、草酸同属有机酸,但因二者的酸性、挥发性、溶解性等不同,致使温度、时间两因素对纤维降解的影响相关很大。盐酸、硫酸无机强酸,都要求高温短时,但随着浓度的升高,转化度呈下降趋势,且二者的下降幅度不同,硫酸大于盐酸。     

裂解性多糖单加氧酶HcLPMO与纤维素酶协同降解纤维素

【目的】为研究HcLPMO的活性测定方法及其与纤维素酶的协同降解特性。【方法】利用大肠杆菌表达系统进行HcLPMO异源表达,研究以AmplexTM Ultra Red为荧光底物的LPMOs活性检测条件;研究HcLPMO与纤维素酶最优配比协同降解微晶纤维素及其他多种生物质底物的能力。【结果】表达条件确定最适装液量为20%,最适诱导温度为20°C。活性测定研究结果表明HcLPMO需先与铜离子结合才具有活性,电子供体抗坏血酸钠(ASC)最适浓度为10–4 mol/L,并发现AmplexTM Ultra Red浓度以及辣根过氧化物酶浓度对酶活的检测影响较小。HcLPMO与纤维素酶协同降解微晶纤维素研究确定HcLPMO与纤维素酶最优配比为2:3,葡萄糖产量相较纤维素酶单独作用提高了99.48%。此外,针对多种生物质底物,发现该酶与纤维素酶的复配体系对汽爆玉米秸秆和微晶纤维素的协同降解效果较好,相较于单独用纤维素水解酶,葡萄糖产量分别提高了63.81%和59.43%,而对碱处理玉米芯和木薯渣降解效果次之,葡萄糖产量仅分别提高35.41%和11.06%。【结论】HcLPMO与纤维素酶复配能够有效提高酶法降解纤维素效率;而底物前处理如蒸汽爆破或碱处理对于HcLPMO与纤维素酶协同降解木质纤维素影响较大。     

正交实验法对碱性磷酸酶活性测定的优化

碱性磷酸酶(ALP)是一种非特异性磷酸单酯酶,碱性条件下几乎能催化所有磷酸单酯的水解。采用正交实验法研究兔肝ALP的活性,在单因素实验的基础上,利用Minitab对碱性磷酸酶的催化条件(pH值、反应温度、酶量、底物量)进行4因素3水平的正交实验设计。正交实验结果表明,4种因素对酶活性的影响由大到小排列顺序为pH值温度底物酶,最佳组合为A3B3C1D1,即酶量为0.4 mL,底物量为0.8 mL,温度50℃,pH值为10时兔肝ALP的活性最强。     

Study on Optimal Conditions of Degradation of Wheat Straw by Cellulase and Analysis of Kinetics

以小麦秸秆为原料,通过正交实验对纤维素酶降解秸秆纤维的影响因素进行了研究.结果表明,影响小麦秸秆降解的因素依次为:酶量＞酶解时间＞料液比＞反应温度,其最适条件是:加酶量为40 u/g,酶解时间为10h,反应温度为40℃,料液比为1∶3,总糖含量达到43.24％.以米氏方程为基础,建立起最适酶解条件下总纤维素降解的动力学模型.     

一株产纤维素酶的甲醇利用细菌的鉴定及其纤维素降解条件优化

采用刚果红染色法,从废弃矿山周边土壤中筛选出一株产纤维素酶的甲醇利用细菌,命名为xt-04。形态特征、生理试验及16SrDNA序列和gyrB序列分析表明,该菌株属于Bacillusmethylotrophicus。为提高该菌所产纤维素酶的降解能力,首先通过单因子实验考察了底物CMC—Na浓度、反应温度及缓冲液pH值对纤维素酶活力的影响;然后采用响应面分析法对影响纤维素酶活力的3个单因子进行了优化。结果表明,单因素实验得出的适宜反应温度、缓冲液pH和底物浓度分别为70℃、5．0和2％（20mg／mL）;响应面法得出的最高酶活力条件：反应温度、pH和底物浓度分别为66．1℃、4．81和19．01mg／mL。在最优条件下,酶活力达到17．85U／mL,比优化前的酶活力12．84U／mL提高了39．01％。因此,鉴于这种纤维素酶能耐受较高温度和酸性条件,该菌株所产纤维素酶可能在工业中具有良好的应用前景。     

纤维素酶在木质纤维素生物质转化中的应用研究

选育得到纤维素酶高产菌株里氏木霉突变菌株(Trichoderma reesei) 813A,优化了其发酵产酶条件。利用该菌株所产纤维素酶对天然木质纤维素的水解糖化过程进行研究,确定了实验条件下最优的糖化条件(温度50℃, pH 4.5,酶浓度6～8 FPU/mL,底物浓度2%)。以玉米叶和杨树叶为天然纤维素原料,水解糖化率分别达到86.2％和56.0%。通过酿酒酵母(Saccharomyces cerevisiae)将糖化液转化为酒精,产乙醇浓度达到 5%～5.8%,转化率为79.4%～92.1%。     

玉米秸秆酶水解过程中的酶复配条件优化

降低酶解成本是纤维素乙醇生产的关键。利用酶复配技术优化蒸汽爆破处理后玉米秸秆的酶水解工艺条件,以提高纤维素的转化率。通过单因素实验和正交实验,研究了纤维素酶、木聚糖酶和β-葡萄糖苷酶对酶解效率的影响规律。结果表明,汽爆玉米秸秆,纤维素含量达42.21%,半纤维素仅为3.65%。纤维素酶对酶解过程起决定性作用,添加40 FPU/g时,酶解率为75.45%;木聚糖酶可促使更多的纤维素暴露出来,添加1 500 IU/g时,酶解率最高为78.03%;β-葡萄糖苷酶有助于消除纤维二糖积累造成的反馈抑制,用量40 IU/g时,纤维二糖浓度为0.330 4 g/100 m L,酶解率达76.45%。正交实验确定最佳工艺为:纤维素酶用量30 FPU/g,木聚糖酶用量800 IU/g,β-葡萄糖苷酶用量40 IU/g;该条件下,进行底物质量浓度25%的验证实验,葡萄糖达9.3g/100 m L,若用单一天冠纤维素酶,葡萄糖仅5.9 g/100 m L,提高了57.63%。三种酶的影响顺序为:纤维素酶木聚糖酶β-葡萄糖苷酶。     

一株玉米秸秆纤维素分解菌株的分离鉴定及酶学性质

【目的】筛选分离可以分解玉米秸秆纤维素的菌株。【方法】采用平板稀释法从土样中分离纯化得到能够分解玉米秸秆纤维素的菌株,对分离得到的菌株进行生理生化及分子鉴定,同时以菌株Penicillium spp.(CICC40361)作为对照,比较菌株纤维素酶和木质素酶的活性,研究不同因素对菌株纤维素酶活力的影响,确定菌株纤维素酶动力学常数Km值。【结果】分离得到的菌株命名为PL2#,经生理生化及分子鉴定后,确定菌株PL2#为羊毛状青霉(Penicillium lanosum)。菌株PL2#的纤维素酶和木质素酶活力高于对照菌株Penicillium spp.;菌株PL2#的最优酶活测定条件为:1%CMC底物浓度,pH 4.8,50°C,酶反应时间60 min以及2 m L DNS添加量。【结论】羊毛状青霉(Penicillium lanosum)菌株PL2#比对照菌株Penicillium spp.具有更好地降解玉米秸秆纤维素的性能。     

Identification and optimal degradation conditions for cellulase-degrading enzyme of a methanol-utilizing and cellulase-producing bacterium

采用刚果红染色法,从废弃矿山周边土壤中筛选出一株产纤维素酶的甲醇利用细菌,命名为xt - 04.形态特征、生理试验及16S rDNA序列和gyrB序列分析表明,该菌株属于Bacillus methylotrophicus.为提高该菌所产纤维素酶的降解能力,首先通过单因子实验考察了底物CMC -Na浓度、反应温度及缓冲液pH值对纤维素酶活力的影响;然后采用响应面分析法对影响纤维素酶活力的3个单因子进行了优化.结果表明,单因素实验得出的适宜反应温度、缓冲液pH和底物浓度分别为70℃、5.0和2％ (20 mg/mL);响应面法得出的最高酶活力条件:反应温度、pH和底物浓度分别为66.1℃、4.81和19.01mg/mL.在最优条件下,酶活力达到17.85 U/mL,比优化前的酶活力12.84 U/mL提高了39.01％.因此,鉴于这种纤维素酶能耐受较高温度和酸性条件,该菌株所产纤维素酶可能在工业中具有良好的应用前景.     

鲜鹿茸酶降解过程的研究

研究了胰蛋白酶、Alcalase 碱性蛋白酶、木瓜蛋白酶对鲜鹿茸的降解过程,确定了优化降解工艺条件,具有一定的理论意义和实践价值。确定了Alcalase 碱性蛋白酶的降解效率最高,通过单因素实验确定了降解过程中底物浓度、酶解温度、pH值和酶解时间为影响鲜鹿茸降解率的主要因素。正交试验确定最佳的酶解条件为:底物浓度0.08 g/ml、酶解温度65 ℃、pH 9.0、酶解时间6.0 h。在此条件下,鲜鹿茸降解率高达92.6%,氨基酸产品收率达12.1%。     

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.