大肠杆菌EP8—10转化苯丙酮酸生成L—苯丙氨酸的研究

E. coli EP8-10 was selected from the soil. It was able to produce the transaminase with high activity when it was cultivated on the medium containing peptone and beef extract. Optimum conditions of enzyme reaction was: phenylpyruvic acid's concentration of 0.3-0.5 mol/L, L-Asptaric acid used as amino donor, pH 8.5 37 degrees C. When phenylpyruvic acid was 0.3 mol/L, 48 g/L L-phenylalanine was produced after 6 h with 97% conversion rate.     

大肠杆菌EP8-10转化苯丙酮酸生成L 苯丙氨酸的研究

分类号Ｑ５１７文献标识码Ｂ文章编号０００１６２０９（１９９９）０３０２７２７４Ｌ苯丙氨酸（ＬＰｈｅ）是一种重要的氨基酸,用于氨基酸输液和二肽甜味剂的生产。近十年来有关ＬＰｈｅ生产的研究非常活跃,其中之一是利用转氨酶由苯丙酮酸（ＰＰＡ）生产…     

产碱菌（Alcaligenes sp.）119转化苯丙酮酸形成L—苯丙氨酸的研究

从土壤中分离到一株产碱菌１１９,能将苯丙酮酸一步转化成Ｌ－苯丙氨酸。酶反应的最适ｐＨ为８．５,该酶在ｐＨ８－９之间稳定,最适反应温度为３７－４５℃,金属离子Ｆｅ＾２＋,Ｍｎ＾２ｎ等对酶有不同程度的抑制作用。该菌株培养在由葡萄糖,蛋白胨、牛肉膏等组成的培养基中,可获得最高转化率。Ｌ－天冬氨酸为酶反应的最佳氨基供体。当苯丙酮酸浓度为０．２ｍｏｌ／Ｌ时,细胞在３７℃下反应１６小时,可产Ｌ－苯丙氨酸３０．     

利用固定化酵母细胞转化反式肉桂酸生产L—苯丙氨酸

研究了深红酵母（Ｒｈｏｄｏｔｏｒｕｌａｒｕｂｒａ）的培养基成分,培养固定化及转化条件,实验表明最佳基成分（％）葡萄糖０．５,胰蛋白胨０．５,酵母膏０．５,磷酸二氢钾０．０５,Ｌ－Ｐｈｅ０．０５,ｐＨ７．０,３０℃２０Ｌ发酵罐中培养１５～１７ｈ,最佳固定化条件为：用２．５％卡拉胶包埋１８％的湿菌体,最佳转化条件为：１．０％反式肉桂酸,４ｍｏｌ／Ｌ铵离子,ｐＨ０．５,３０℃,用卡拉胶固定化深红酵母（Ｒ     

酵母细胞生物转化反式—肉桂酸生产L—苯丙氨酸的研究

据文献调查,搜集了国内可能相关的30株酵母,进行生物转化反式-肉桂酸(t-Ca) 生产L-苯丙氨酸 (L-Phe) 的微生物筛选研究,并对部分菌株生物转化能力,即苯丙氨酸解氨酶 (PAL,EC _(4、3、1、5) 活性水平进行了初步评估。筛选结果是:22株酵母具有转化 t-Ca 生成 L-Phe 的能力,转化率在2—67％范围。选出7株酵母研究在液体培养条件下细胞生长和PAL活性的时间过程关系,PAL 活性范围在 2.3—14.4x10~(-s)u/m g细胞干重。深红酵母 (Rhodotorularubra) AS2.166作为生物转化制备实经菌株,在静止细胞和固定化细胞批式反应条件下,结果获得L-Phe分离产率分别为42.0％,28.7％。     

E.ColiA.S1.588生产L—天门冬酰胺酶发酵工艺的研究

Ｅ·ＣｏｌｉＡ·Ｓ１．５８８生产Ｌ－天门冬酰胺酶发酵工艺的研究陈丽媛,金守满,刘薇,陆春左,元福实（辽宁省微生物研究所,朝阳１２２０００）Ｌ一天门冬酰胺酶（ＥＣ３．５．１．１）即Ｌ一天门冬酰胺酰胺基水解酶,专一催化Ｌ一天门冬酰胺水解形成Ｌ一天门冬氨酸...     

L—赖氨酸产生菌FH128菌株的研究：（Ⅰ）FH菌株的选育及摇瓶发酵

以赖氨酸产生菌Ａ１１１（ＨＳ＾－,ＡＥＣ＾ｒ）为出发株,经化学诱变剂ＭＮＮＧ（Ｎ－’－硝基－Ｎ－亚硝基胍）及单氟醋酸处理获得单氟生突变株Ｆ７９,摇瓶发酵产Ｌ－赖氨酸盐酸盐７．０％－７．５％,对糖转化率３８％－４０％,分别比Ａ１１１株提高红２５％及２０％。     

骨髓高增殖潜能集落形成细胞（HPP—CFC）分化产生巨核细胞的研究

本研究用正常和５－ＦＵ处理的小鼠骨髓细胞,作血浆凝块培养,对一种称作ＨＰＰ－ｍＣＦＵ－ＭＫ的ＨＰＰ－ＣＦＣ亚型细胞集落进行体外追踪。发现ＨＰＰ－ｍＣＦＵ－ＭＫ不但能形成符合ＨＰＰ－ＣＦＣ标准的巨大集落,而且能产生大量的巨核细胞。该巨大集落的生长,依赖添加再生障碍性贫血猪血清（ＡＡＳ）或合用三种以上的基因重组造血生长因子而增强,在体外不被ＴＧＦ－β１和ＰＦ４抑制。原代培养１２天所得到的ＨＰＰ－ｍＣＦ     

大肠杆菌细胞的软X射线显微成像研究

软X射线显微术是研究含水甚至活性生物样品的有力工具。相对于光学显微镜 ,它具有更高的成象分辨率 ;相对于电子显微镜 ,它的样品制备简单—无须对样品进行脱水、染色和超薄切片等。报道的是利用合肥同步辐射X射线源和接触显微成象技术 ,对自然状态下含水的完整XL1 blueMRF′细菌细胞进行显微成象研究。从获得的显微图象中可以看出一些新的现象。含有DNA、蛋白质的拟核以及中体对波长 2 .4nmX射线具有较弱的吸收能力 ;不少细菌细胞的两端对 2 .4nm波长的X射线的吸收也具有很大的差异。这些有趣现象产生的根本原因和生物学意义有待进一步研究。     

Kinetic Equations for L-Phenylalanine Production by a Hyperproducing Mutant of Escherichia Coli

Using a set of kinetic equations, which take account of the effect of both intra-and extracellular phosphate concentrations, the batch culture production of L-phenylalanine by a hyperproducing mutant of E. coli has been described. Good agreement has been found between the predicted results and experimental data for cell growth, glucose uptake, phosphate uptake and L-phenylalanine production for initial glucose concentrations of 16 and 26 g. L^-1. The kinetic model is applicable to conditions for which no substrate inhibition or product inhibition are likely to occur.     

整合子与多重耐药大肠埃希菌相关性研究

目的探讨整合子在多重耐药大肠埃希菌耐药性中的作用。方法对临床分离的93株多重耐药大肠埃希菌的I、Ⅱ型整合酶基因进行检测,并分析药敏结果。结果多重耐药临床分离株中Ⅰ型整合子阳性率为60.2%。所检出整合子共有3种长度即1000、1600和2000 bp;主要携带aadA和dfrA类基因盒;未检出Ⅱ型整合子。结论整合子形成是细菌产生多重耐药的重要原因。     

大肠杆菌周质蛋白提取工艺的研究

研究了精氨酸缓冲液在不同浓度、pH值及提取时间下的周质蛋白提取率,并以溶菌酶法、渗透压休克法作为对比。结果表明浓度0.4 mol/L,pH值8.0,提取时间为45 min时,周质目的蛋白达到0.89 mg/g湿菌,相比其他方法,周质蛋白提取率分别提高93%、187%。实验得到一种高效、方便的大肠杆菌周质蛋白提取工艺,为周质表达的重组蛋白大规模生产奠定了基础。     

Uropathogenic Escherichia coli (UPEC) strains may carry virulence properties of diarrhoeagenic E. coli

To analyze whether Escherichia coli strains that cause urinary tract infections (UPEC) share virulence characteristics with the diarrheagenic E. coli (DEC) pathotypes and to recognize their genetic diversity, 225 UPEC strains were examined for the presence of various properties of DEC and UPEC (type of interaction with HeLa cells, serogroups and presence of 30 virulence genes). No correlation between adherence patterns and serogroups was observed. Forty-five serogroups were found, but 64% of the strains belonged to one of the 12 serogroups (O1, O2, O4, O6, O7, O14, O15, O18, O21, O25, O75, and O175) and carried UPEC virulence genes (pap, hly, aer, sfa, cnf). The DEC genes found were: aap, aatA, aggC, agg3C, aggR, astA, eae, ehly, iha, irp2, lpfA(O113), pet, pic, pilS, and shf. Sixteen strains presented aggregative adherence and/or the aatA sequence, which are characteristics of enteroaggregative E. coli (EAEC), one of the DEC pathotypes. In summary, certain UPEC strains may carry DEC virulence properties, mostly associated to the EAEC pathotype. This finding raises the possibility that at least some faecal EAEC strains might represent potential uropathogens. Alternatively, certain UPEC strains may have acquired EAEC properties, becoming a potential cause of diarrhoea.     

RAPID detection and quantification of E. coli O157/O26/O111 in minced beef by real-time PCR

AIM: To develop a real-time PCR detection procedure for Escherichia coli O111, O26 and O157 from minced meat. METHODS AND RESULTS: Strains (n = 8) of each of E. coli O26, E. coli O111 and E. coli O157 were inoculated at ca 10-20 CFU g(-1) into minced retail meat and enriched for 6 h at 41.5 degrees C as follows: E. coli O26 in tryptone soya broth (TSB) supplemented with cefixime (50 microg l(-1)), vancomycin (40 mg l(-1)) and potassium tellurite (2.5 mg l(-1)); E. coli O111 in TSB supplemented with cefixime (50 microg l(-1)) and vancomycin (40 mg l(-1)); E. coli O157 in E. coli broth supplemented with novobiocin (20 mg l(-1)). DNA was extracted from the enriched cultures, and detected and quantified by real-time PCR using verotoxin (vt1 and vt2) and serogroup (O157 per gene; O26 fliC-fliA genes and O111 wzy gene) specific primers. CONCLUSIONS: The methods outlined were found to be sensitive and specific for the routine detection of E. coli O111, O26 and O157 in minced beef. SIGNIFICANCE AND IMPACT OF THE STUDY: The enrichment, isolation and detection procedures used in this study provide a rapid routine-based molecular method for the detection and differentiation of E. coli O26, O111 and O157 from minced meat.     

Characterization of adhesion zones in E. coli cells

After plasmolysis of Escherichia coli cells, the adhesion zones were characterized using the cytochemical PTA and SP procedures which stain peptidoglycan and lipopolysaccharides (LPS) respectively. A PTA-stained layer was detected at the adhesion sites. This layer was visualized irrespective of the electron microscopy procedure used. Also, using SP staining an outer membrane in which LPS molecules were asymmetrically distributed, was observed.     

大肠杆菌腺苷脱氨酶基因的克隆表达

将大肠杆菌K12菌株来源的腺苷脱氨酶基因(add)克隆到载体pET-28a中,并转化至大肠杆菌BL21(DE3)中进行表达。通过IPTG诱导,SDS-PAGE检测和酶活性的测定发现,重组菌表达产生大量腺苷脱氨酶,活性达到51.07U/mg蛋白。通过酶性质的研究,腺苷脱氨酶对腺苷最适pH和温度分别为7.5和40℃,且在40℃下维持稳定。