产1,3-丙二醇菌株丁酸梭菌的诱变育种

甘油由丁酸梭菌转化成1,3-丙二醇的研究是厌氧条件下进行。为了获得1,3-丙二醇的高产突变株,以丁酸梭菌为出发菌株进行诱变处理。经过硫酸二乙酯（DES）化学诱变得到2株高产正突变株C.but2031和C.but2046,再经过紫外线和亚硝基胍（NTG）复合诱变得到突变株C.but3037。经过初筛、复筛和传代实验,表明其是稳定的突变株。C.but3037的1,3-丙二醇产量由出发菌株的2.2g/L提高到15.7g/L,提高了6.13倍,     

一株在有氧条件下转化丙酮醇为1,2-丙二醇的大肠杆菌菌株的研究

本实验室在前期构建了一株能高效利用甘油合成丙酮醇的大肠杆菌工程菌株,如果能在有氧条件下将丙酮醇转化为1,2-丙二醇,则可以大幅提高1,2-丙二醇的合成速率。以大肠杆菌BW25113Δglp K为出发菌株,筛选得到一株可以在有氧条件下代谢甘油的突变菌株PDO1。结果表明,该菌株可以在有氧条件下将丙酮醇转化为1,2-丙二醇,1,2-丙二醇的产量达到0.73 g/L,转化率达到0.493 g/g丙酮醇。突变株PDO1的甘油脱氢酶酶活和胞内的NADH百分比分别是对照株的75.9倍和1.64倍,由此推测,甘油脱氢酶酶活的提高以及NADH的相对提高,使得突变株可以在有氧条件下通过甘油脱氢酶途径代谢甘油,并转化丙酮醇为1,2-丙酮醇。     

原生质体紫外诱变技术选育1,3-丙二醇高产菌株

以肺炎克雷伯氏杆菌(Klebsiella pneumoniae)为研究对象,应用原生质体紫外诱变技术提高其对甘油及1,3-丙二醇的耐受性,获得1,3-丙二醇高产菌.在原生质体制备过程中,运用滤膜去除酶解后细胞悬液中的正常菌体,简化菌体酶解过程,提高再生率及形成率.经过原生质体诱变后,以耐受高浓度甘油和1,3-丙二醇及高产酸能力为筛选方向,最终筛选到了3株高产菌株(Kp-1、Kp-4和Kp-5).在补料发酵实验中,上述诱变菌产1,3-丙二醇能力分别为70.24 、65.21和75.51 g/L,比野生菌株WT(55.78 g/L)分别提高了25.92%、16.91%和35.37%.     

产1,3-丙二醇菌株的诱变和筛选

为提高克雷伯氏肺炎杆菌产1,3-丙二醇的能力,以离子束、紫外线和氯化锂为复合诱变法,建立了产酸圈和产物耐受相结合的平板筛选方法,获得可耐受高浓度1,3-丙二醇并且副产物中乙醇含量较少的优良突变菌株2株。与出发菌株相比,两株高产突变菌株Klebsiella pneumoniae LM 03和Klebsiella pneumoniae LM05的1,3-丙二醇产量分别提高了33% 和30% ,达到66.74 g/L和65.12 g/L;乙醇产量分别降低了38% 和24% ,降低为6.59 g/L和8.05 g/L。同时测定了诱变前后还原途径中甘油脱水酶（GDHt）和1,3-丙二醇氧化还原酶（PDOR）的酶活变化,研究表明诱变对GDHt有明显的促进作用,而对PDOR的影响不明显。该诱变和筛选方法目标明确、易操作、效率高,在1,3-PD工业规模的生物法生产中将具有良好的应用价值,而且对于其他具有工业应用价值的菌株筛选工作也具有一定的借鉴意义。     

原生质体诱变选育高产异抗坏血酸菌株

以灰黄青霉菌(Penicillium griseofulvum HL)为出发菌株,试验得到灰黄青霉原生质体制备的优化条件为:菌体培养48h,用0.7mol/L的NaC1溶液作为渗透压稳定剂,用0.5％的蜗牛酶+0.5％的纤维素酶,在pH为6,30℃条件下酶解3h,所得原生质体数最多,达到3.14×107/ml.原生质体再生的最佳条件为采用双层平板培养法,在用0.7mol/L的蔗糖溶液配制的改进察氏培养基上其再生率最高,达到24.93％.灰黄青霉原生质体经过紫外线诱变,DES诱变,紫外线-DES诱变复合诱变,紫外线-氯化锂复合诱变选育异抗坏血酸高产菌株,通过对再生平板上长出的诱变菌株进行初筛和摇瓶复筛,最终获得一株异抗坏血酸产量较高的菌株ZD4,其产量为5.28mg/ml,提高到出发菌株产量(1.08 mg/ml)的488.9％,且连续传代6代遗传稳定.     

1,3-丙二醇产生菌的诱变育种及培养基优化

以实验室自然筛选的克雷伯氏杆菌(Klebsiella sp.)为出发株,采用紫外诱变及亚硝基胍和超声波协同处理获得一株1,3-丙二醇高产突变株。在摇瓶发酵中,其产1,3-丙二醇产量由17.39 g/L提高到24.11 g/L,提高38.64%。变异株经10次传代培养,发酵能力稳定。对发酵培养基成分进行了优化,优化后1,3-丙二醇产量为30.05g/L,为优化前的1.25倍。     

论文中阿拉伯数字的使用克雷伯氏肺炎杆菌HR526快速合成1,3-丙二醇发酵特性研究

研究了实验室筛选的一株高产1,3-丙二醇(PDO)菌株克雷伯氏肺炎杆菌HR526(Klebsiella pneumoniae HR526),在5 L B.Braun发酵罐进行甘油补料流加发酵30 h,PDO达到91.47 g/L,胞外代谢通量分析显示,PDO在对数中期通量达到最大,而乳酸在稳定期通量达到最大.结合酶学检测分析了PDO合成关键酶PDO氧化还原酶(PDOR)、甘油脱水酶(GDHt)和甘油脱氢酶(GDH)酶活的变化,PDO氧化还原酶活性在对数中期达到最高,甘油脱水酶/甘油脱氢酶在对数期远大于稳定期、衰退期,与代谢通量变化一致甘油脱水酶/甘油脱氢酶活性比例不均衡是3-HPA对数期积累的原因,PDO合成主要集中在对数期,是生长偶联的代谢产物.     

积累PHB菌种隐藏嗜酸菌DX1-1的诱变改良

采用紫外线照射和放射性元素钴60辐射诱变方法,对分离纯化的一株可积累聚β-羟基丁酸酯(PHB)的Acidiphilium cryptumDX1-1进行了诱变改良,以获得PHB高产菌.结果显示钴60诱变最佳诱变剂量为100 Gy,紫外诱变的最佳剂量为15 W、30 cm、60 s,紫外诱变的效果比钴60诱变的效果好.诱变后筛选得到的一株菌UV60-3,PHB含量达到28.56 g/L,是原菌株的1.45倍,并且可稳定遗传.对菌株UV60-3积累PHB的碳氮比进行了探索,结果显示在碳源浓度60 g/L,氮源浓度30 g/L,C/N为3.76时PHB含量最高,PHB含量达到30.57 g/L.     

克雷伯氏肺炎杆菌HR526快速合成1,3-丙二醇发酵特性研究

研究了实验室筛选的一株高产1,3-丙二醇(PDO)菌株克雷伯氏肺炎杆菌HR526(Klebsiella pneumoniae HR526), 在5 L B. Braun发酵罐进行甘油补料流加发酵30 h, PDO达到91.47 g/L, 胞外代谢通量分析显示, PDO在对数中期通量达到最大, 而乳酸在稳定期通量达到最大。结合酶学检测分析了PDO合成关键酶PDO氧化还原酶(PDOR)、甘油脱水酶(GDHt)和甘油脱氢酶(GDH)酶活的变化, PDO氧化还原酶活性在对数中期达到最高, 甘油脱水酶/甘油脱氢酶在对数期远大于稳定期、衰退期, 与代谢通量变化一致甘油脱水酶/甘油脱氢酶活性比例不均衡是3-HPA对数期积累的原因, PDO合成主要集中在对数期, 是生长偶联的代谢产物。     

一株1,3-丙二醇生产菌的分离鉴定及其发酵特性

从活性污泥中分离筛选得到一株能代谢甘油生产1,3-丙二醇(1,3-PD)的菌株2-1,通过形态学鉴定、生理生化试验、16S rRNA序列分析对菌株分类学地位进行鉴定,用MEGA 4.1软件构建的系统发育树显示菌株2-1与Klebsiella pneumoniae(CP001891)的亲缘关系最近。16S rDNA序列同源性比较发现,菌株2-1与模式菌株同源率为95.4%,疑似为新种。对菌株2-1在5 L发酵罐中进行发酵特性研究,分批补料发酵时得到较高的1,3-PD终浓度,达到63.5 g/L,此时生产强度为2.19 g/(L.h),底物转化率0.64 mol/mol。     

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.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

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.