产碱性纤维素酶兼性厌氧菌株的筛选和酶学性质的初步研究

用CMC平板筛选方法,从造纸厂碱性土壤中获得产碱性纤维素酶兼性厌氧菌株LZ-5,革兰氏阴性,经鉴定为弧菌属(Vibrio sp.)中的一个种.液体摇瓶培养产生碱性纤维素酶活力高达5.8 U/mL.酶学性质初步研究显示,LZ-5产生的纤维素酶最适反应温度为40℃,最适反应pH值为9.0,在碱性条件下具有较高的酶活性和较好的稳定性.经传代培养证实该菌株遗传性能稳定.     

产碱性纤维素酶嗜碱芽孢杆菌AH-8的研究

从贵州、云南、海南、安徽、四川、辽宁等地采集碱性土样,分离筛选到1株能稳定的产生碱性纤维素酶的嗜碱性芽孢杆菌AH-8。研究表明,该菌株最适产酶温度为37℃,最适发酵时间为36 h;采用均匀设计法对其发酵培养基进行优化,优化培养基配方(%):淀粉3.0,胰蛋白胨1.5,牛肉膏1.5,葡萄糖0.3,KH2PO40.1,初始pH 10.0。在优化培养基条件下,其产酶量提高了120%。碱性纤维素酶最适反应温度为60℃;最适反应pH 10.0;0.01%Co2 对酶活力有一定激活作用。     

产低温纤维素酶放线菌的筛选、鉴定及酶学性质初步研究

从青藏高原采集的牦牛粪中,经过CMC平板分离得到一株产低温纤维素酶能力较强的放菌Tibet-YD5227-2,经16S rDNA序列比对分析将其初步鉴定为链霉菌属(Streptomyces sp.),目前尚无链霉菌产低温纤维素酶的研究报道。Tibet-YD5227-2液体摇瓶培养产生低温CMC酶活力高达145U/mL,最适产酶温度25℃,最适产酶pH值为8.0。酶学性质初步研究显示,Tibet-YD5227-2产生的CMC酶反应温度以35℃左右为适,反应的pH值以8.0左右为适,该菌株所产的纤维素酶在中碱性条件具有较强的稳定性;K+、Fe2+、Mg2+对酶反应有促进作用,Hg2+、Cu2+对酶反应有抑制作用。     

一株产纤维素酶细菌的分离鉴定及酶学特性研究

从采集的含腐烂树叶的土壤中,筛选到1株产纤维素酶能力较高的菌株JJ-3,经16S r RNA基因序列分析,鉴定该菌株为产酸克雷伯氏杆菌(Klebsiella oxytoca)。产酶条件及酶学特性研究表明:以滤纸为碳源、蛋白胨为氮源、初始p H为8.0的培养基中发酵3 d更利于纤维素酶的合成;菌株发酵液在中性和碱性条件下均有较高的滤纸酶活力,分别可达118.7 U/m L(p H7.0),167.8 U/m L(p H8.0)和120 U/m L(p H9.0);所产纤维素酶的最适酶反应p H为7.0,最适酶反应温度为40℃,对温度比较敏感,在p H7.0-8.0的范围内具有较好的稳定性,能满足中性和碱性纤维素酶的要求。     

碱性纤维素酶及其应用的研究进展

碱性纤维素酶在碱性条件下具有内切β-1,4葡萄糖苷酶活力,在加酶洗涤剂等行业具有重要的应用价值。目前已发现由芽孢杆菌和链霉菌产生的多种碱性纤维素酶,其中大部分的基因已被克隆、测序和表达,其催化反应特性、反应机理和应用也得到了较深入的研究。从碱性纤维素酶的产生菌、酶反应特性和反应机理、碱性纤维素酶的基因克隆和表达,以及碱性纤维素酶的应用等几个方面,介绍了有关碱性纤维素酶的最新研究进展。     

高碱性纤维素酶产生菌的筛选及鉴定

从化纤厂土样中分离得到菌株AC-4,碱性纤维素酶活力达0.602 IU/mL。通过分析菌株形态学特性、培养特征及16S rDNA序列,确定该菌株为短小芽孢杆菌。对该菌所产碱性纤维素酶的酶学性质进行测定,确定其最适作用pH为9.5,最适作用温度为50℃。     

芽胞杆菌C14碱性纤维素酶性质的研究

从碱性污泥中分离到一株产碱性纤维素酶活力较高的耐碱性芽胞杆菌,所产的酶为单一的羧甲基纤维素酶,其专一性底物为羧甲基纤维素钠,酶的最适反应ＰＨ为９．０,在ＰＨ７－１０．０范围内较稳定,酶作用的最适温度为５５℃,在５０℃时较稳定,在６０℃处理,１０、３０、６０和９０分钟后,残余酶活分别为９１．５％、７２．０％、３６．６％和１０．３％。Ｃｏ＾２＋,ＥＤＴＡ对酶促反应有明显的促进作用,Ｈｇ＾２＋,Ａｇ＾２     

碱性纤维素酶及其去污机理

纤维素酶的研究,已有四五十年的历史。但是,一直是以木霉（Trichodern。a）、曲霉U印eryillus）属等真菌产生的酸性纤维素酶为研究对象,以将木质纤维素转化成葡萄糖为主要研究方向进行的。近年来,碱性纤维素酶在洗涤剂工业上的成功应用,改变了传统的去污机制,建立了一套新的去污机理,被洗涤剂工业称之为一次技术大革命,使碱性纤维素酶成为世界各国普遍重视的一种极具生命力的新型酶制剂。三产碱性纤维素酶的微生物及其酶的性质碱性微生物可以分为嗜碱菌和耐碱菌。只有在pHS以上才能生长的被称之为嗜碱菌;最适pH是中性,但在碱性…     

洗涤剂用碱性纤维素酶的研究（Ⅱ）——酶的提取及性质

产碱性纤维素酶的嗜碱芽孢杆菌ＳＨＹ８－５７２５发酵液经絮凝预处理后,采用混合盐析方法沉淀酶,盐析收率可达９５％以上,所制得酶粉ＣＭＣａｓｅ可达５００ｕ／ｇ以上。酶的最适ｐＨ为８．０和１０．５,稳定ｐＨ范围为４～１２;最适温度为４５℃（ｐＨ９．０,１０ｍｉｎ）稳定温度范围为５０℃（ｐＨ９．０,３０ｍｉｎ）以下;洗衣粉中各种表面活性剂和助剂对ＣＭＣａｓｅ基本无影响,酶的底物特异性表明,该碱性纤维素酶主     

低温纤维素降解菌的筛选及其酶学性质初步研究

从青藏高原冰川雪样恢复出的4株细菌中筛选出1株降解纤维素能力比较高的菌株LHG-C-9。经16SrDNA序列分析,初步鉴定为假单胞菌属。对该菌所产纤维素酶的性质进行了初步研究,其最适作用温度为30℃;对热敏感;最适pH8．0;属碱性温酶。该低温纤维素酶在纺织、造纸、环保、医药和饲料等行业可望有广泛的应用前景。     

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.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

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.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.