枯草芽胞杆菌甘露聚糖酶发酵条件优化

旨在以枯草芽胞杆菌Bacillus subtilis J为生产菌株,发酵生产β-甘露聚糖酶,通过优化产酶条件,以达到提高β-甘露聚糖酶产量的目的。利用DNS比色法检测β-甘露聚糖酶活力,采用单因素试验,研究碳氮源种类及碳氮源浓度、温度、pH、接种量和装液量对菌株Bacillus subtilis J发酵产β-甘露聚糖酶的影响,结合响应面试验设计确定菌株Bacillus subtilis J发酵产甘露聚糖酶的最优发酵培养条件。单因素试验和响应面试验得到最优的发酵条件为魔芋粉28 g/L,胰蛋白胨21 g/L,K₂HPO₄ 6 g/L,MgSO₄·7H₂O 1 g/L,温度31℃,pH值8.5,接种量1%(体积分数),装液量50 mL/250 mL,发酵周期24 h。利用优化后的培养基生产β-甘露聚糖酶,其酶活力达到84.38 U/mL,是初始发酵培养基产酶活力的3.36倍。通过对发酵条件的优化,大幅度提高了β-甘露聚糖酶的产量,为其工业生产提供参考。     

一株产甘露聚糖酶菌株的分离鉴定及酶的纯化与性质

【目的】筛选性能良好的产碱性甘露聚糖酶的菌株,对菌株进行多项分类鉴定,分离纯化所产甘露聚糖酶并进行性质研究。【方法】利用碱性魔芋粉培养基分离纯化产甘露聚糖酶的嗜碱菌,通过形态特征观察、生理生化测定、16S rRNA序列分析等实验确定菌株的分类地位。利用硫酸铵沉淀、阴离子交换层析和分子筛层析得到电泳纯的酶,分析了酶的最适温度、最适pH、温度和pH稳定性、NaCl以及金属离子等的耐受性。【结果】从我国内蒙古碱湖样品中分离得到一株产碱性甘露聚糖酶的菌株HMTS15,经过多项分类鉴定显示其是与Bacillus agaradhaerens DSM 8721不同的新菌株。菌株HMTS15所产的甘露聚糖酶反应的最适pH为10.0,最适温度75℃。【结论】多项分类结果鉴定菌株为Bacillus agaradhaerens HMTS15。该菌株产生的碱性甘露聚糖酶与同类其他来源的酶相比具有更好的热稳定性和pH适应性,有进一步的研究价值。     

β-甘露聚糖酶产生菌的分离、鉴定及产β-甘露聚糖酶最适条件的研究

以采集的土壤样品为试验材料,经过富集培养及分离纯化,筛选出2株产β-甘露聚糖酶的菌株.采用摇瓶培养分别测定其酶活力,其中1株菌株酶活力较高,酶活力达50.36 U/ml.生理生化性质鉴定及16S rDNA序列相似性结果表明该菌为假单孢菌(Pseudomonas sp.).产酶的最适条件研究发现,1 g/100 ml玉米粉,2 g/100 ml魔芋粉,pH6.0,32℃为最优产酶条件,酶活力达185.37 U/ml,是优化前的3.68倍.该菌产酶迅速,培养12 h后已达产酶高峰.粗酶的性质研究发现,该酶是一种酸性的甘露聚糖酶,作用的最适pH为4.0,最适反应温度为55℃;该酶的稳定性较好,在pH4.0～6.0、温度为40～55℃保持较好的稳定性.     

高温蛋白酶产生菌的筛选及其产酶条件和酶学性质分析

从徂徕山温泉附近土样中分离到9株产高温蛋白酶菌株,选取一株碱性蛋白酶高产菌株L7为出发菌株,进行显微形态、16S rRNA基因序列分析,将其初步鉴定为短芽孢杆菌(Brevibacillus sp.)。研究该菌株发酵条件,确定产酶的最佳培养基组成为葡萄糖40 g/L,蛋白胨20 g/L,磷酸氢二钠1.4 g/L,氯化钙0.6 g/L,硫酸镁0.4 g/L,通过培养基优化,酶活达到103.08 U/mL。最佳培养条件为250 mL三角烧瓶中装液量50 mL、pH8.0、培养温度为55℃、培养时间为24 h。对该菌株酶学性质研究,L7菌株所产高温蛋白酶的最适温度为55℃,最适pH为10,并且具有良好的温度稳定性和pH稳定性,酶活性受PMSF强烈抑制。     

β-甘露聚糖酶产生菌R10的产酶特性研究

分离出一株能利用魔芋飞粉和魔芋精粉生产β-甘露聚糖酶的解淀粉芽孢杆菌(Bacillus amyloliquefaciens)R10。其摇瓶最适发酵条件为：魔芋飞粉1％(m／m),魔芋精粉2％(m／m),160r/min,37℃培养10h。实验结果表明β-甘露聚糖酶的最适作用温度为60℃,最适作用pH为6．0。魔芋葡甘露聚糖经酶降解后为一系列低聚糖。     

枯草芽孢杆菌产β-甘露聚糖酶固体发酵条件的优化*

芽孢杆菌是产甘露聚糖酶的优良菌株,首次研究芽孢杆菌固体发酵条件的优化。以天然麸皮作为基本原料,研究利用枯草芽孢杆菌WY34固体发酵生产β-甘露聚糖酶的发酵条件。最佳固体发酵培养条件为:麸皮5 g,初始水分含量71%,初始pH 7.0,接种量为2 mL,1%Tween-80,0.4 g魔芋粉,培养温度50℃。在最适条件下培养5 d,甘露聚糖酶酶活高达7,650 U/g干基,是未优化前酶活的2.78倍。     

枯草芽孢杆菌中性β-甘露聚糖酶的产生及性质

由土壤中分离出一株产中性β甘露聚糖酶的枯草芽孢杆菌(Bacillus subtilis),编号BM9602。该菌在液体培养条件下,产生中性β甘露聚糖酶。多糖能作为碳源,而单糖不能作为碳源;有机氮源优于无机氮源。产酶最适培养基组成：魔芋粉4%,牛肉蛋白胨和酵母膏各1%。产酶最适培养条件：培养基起始pH85,35℃,振荡培养36〖KG*3]h。以槐豆胶为底物,培养滤液中性β甘露聚糖酶活力为96IU/mL。酶在pH50～100和50℃下稳定;作用最适条件为pH60和50℃;水解魔芋粉和槐豆胶均产生寡聚糖。     

酸性β-甘露聚糖酶的固体发酵和一般特性

研究了培养基组分和培养条件对黑曲霉WM20-11菌株合成β-甘露聚糖酶的影响。最适培养基和发酵条件为：水12mL,麸皮8g,豆饼粉2g,魔芋粉0.4g,玉米浆0.5mL,(NH4)2SO4 1.0%,CaCl2 0.1%、MgSO4 0.1%,KH2PO4 0.2%(相对于固体料的百分数）,自然pH:31-32℃固体静置培养84h,WM20-11产β-甘露聚糖酶活力达1295U/g干曲。该酶最适作用温度和pH分别为70℃和3.5;在pH2.5-7.0之间稳定,保温30min的半失活温度t1/2为58℃;Ca^2 对酶有激活作用,而Pb^2 、Co^2 、Fe^3 对酶有抑制作用。     

枯草芽孢杆菌产β-甘露聚糖酶固体发酵条件的优化

芽孢杆菌是产甘露聚糖酶的优良菌株,首次研究芽孢杆菌固体发酵条件的优化。以天然麸皮作为基本原料,研究利用枯草芽孢杆菌WY34固体发酵生产β-片露聚糖酶的发酵条件。最佳固体发酵培养条件为：麸皮5g,初始水分含量71％,初始pH7．0,接种量为2mL,1％Tween-80,0.4g魔芋粉,培养温度50℃。在最适条件下培养5d,甘露聚糖酶酶活高达7,650U／g干基,是未优化前酶活的2．78倍。     

芽孢杆菌β-甘露聚糖酶基因的克隆及表达

从新疆极端干燥环境土壤样品中筛选到具有高β-甘露聚糖酶活性的芽孢杆菌(Bacillus sp.MX).运用PCR技术从该菌基因组中克隆得到β-甘露聚糖酶基因,连接到表达载体pET-28a上.在大肠杆菌BL21中高效表达的基因产物经亲和层析纯化,SDS-PAGE凝胶电泳分析显示该蛋白的相对分子质量为41 kD.酶学性质分析表明该酶在25～95℃,pH3.0～9.6范围内均具有酶活.最适作用温度55℃和pH值5.0,酶比活力为4 572 U/mg.在最适pH 5.0,高温85℃和95℃分别处理10min后,该酶相对酶活力仍保持51%和34%,显示β-甘露聚糖酶具有较好的耐酸性和热稳定性.     

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.