溶氧量与谷氨酸棒杆菌代谢

正自从1957年Kinoshita等首次描述谷氨酸棒杆菌(Corynebacterium glutamicum)为谷氨酸产生菌[1]以来,其已成为用于氨基酸生产的主要菌株。目前,全世界每年利用谷氨酸棒杆菌生产约100万t L-谷氨酸用于食品调味剂和约45万t L-赖氨酸用作食品添加剂[2]。通过谷氨酸棒状杆菌发酵获得谷氨酸的发酵水平已较高,通过进一步优化工艺来提高产量具有较大困难[3]。     

基于微生物同化作用的D-丙氨酸生产工艺研究

以L-丙氨酸为唯一碳氮源,从采集的若干土壤中初筛出能够降解L-丙氨酸的菌株;再以D-丙氨酸为唯一碳氮源,复筛出降解L-丙氨酸而不降解D-丙氨酸的菌株。依据菌种对DL-丙氨酸的不对称降解活性,筛选出具有最高的L-丙氨酸降解活性的菌株,并对菌株同化L-丙氨酸的反应条件进行了研究。结果表明:编号为ALA-D82的菌株具有最高的降解L-丙氨酸的能力,经鉴定为酵母菌属。在30℃,控制pH6.0,通气比1:1(V/V)和转速900 r.min-1的条件下,L-丙氨酸降解的速度最大。在最适条件下,1500 g DL-丙氨酸分两部分添加入7 L的反应液中。反应72 h后溶液中的L-丙氨酸被完全降解,提取得到D-丙氨酸晶体,产率和光学纯度分别达到92.13%和99%。     

重组大肠杆菌转化富马酸生产L-丙氨酸

通过克隆来源于睾丸酮丛毛单胞菌的L-天冬氨酸-β-脱羧酶基因,在一株具有L-天冬氨酸酶生产能力的大肠埃希氏菌CICC 11022S中异源表达,构建转化富马酸生产L-丙氨酸的重组工程菌。结果发现:重组工程菌9 h转化富马酸产生112.7 g/L的L-丙氨酸,生产速率12.5 g/(L·h),转化率93.8%。富马酸价格较低,有效降低L-丙氨酸生产的原料成本。通过构建重组工程菌,以富马酸为底物,高效生产L-丙氨酸,结果表明该方法具有较好的工业应用潜力。     

膜法提取L-丙氨酸工艺研究

本文研究针对发酵法生产的L-丙氨酸。首先将L-丙氨酸发酵液加热预处理,用陶瓷超滤膜除去发酵液中菌体、大分子蛋白等杂质得到超滤液,然后将超滤液经纳滤膜除去色素、小分子蛋白、无机盐得纳滤液,纳滤液再经过真空浓缩、结晶、离心、烘干、包装得到L-丙氨酸成品。L-丙氨酸离心母液返回至纳滤工序套用,最终总提取平均收率大于91%,产品质量符合日本味之素企业(AJI97)和中国企业(食品级)标准。     

温度调节基因开关调控大肠杆菌发酵合成L-丙氨

【目的】L-丙氨酸的存在导致Escherichia coli的生长速率显著降低,最终会降低发酵过程中L-丙氨酸的体积合成速率。用温度调节基因开关(λpR-pL)高效、动态调控重组E. coli菌株菌体生长与L-丙氨酸合成过程,使两者相协调。【方法】以野生型E. coli B0016为出发菌株,敲除乙酸、甲酸、乙醇、琥珀酸、乳酸代谢产物合成途径以及丙氨酸消旋酶编码基因(ackA-pta、pflB、adhE、frdA、ldhA、dadX),获得菌株B0016-060B。将嗜热脂肪地芽孢杆菌(Geobacillus stearothermophilus)来源的L-丙氨酸脱氢酶基因(alaD)克隆于pL启动子下游,并在B0016-060B菌株中表达,获得菌株B0016-060B/pPL-alaD,进行摇瓶和发酵罐发酵考察菌体生长和L-丙氨酸发酵性能。【结果】竞争代谢途径的敲除显著降低了副产物合成量,仅形成极少量的乙酸、琥珀酸和乙醇。28 °C下菌株B0016-060B/pPL-alaD几乎不合成L-丙氨酸,可保证菌体快速生长;而在42 °C下可高效合成L-丙氨酸。经发酵罐发酵,可合成67.2 g/L L-丙氨酸,体积生产强度达到2.06 g/(L·h)。【结论】通过发酵培养温度的简单切换,分阶段实现了细胞的快速增量和L-丙氨酸的高强度合成。     

香菇复配氨基酸培养基优化及其对香菇菌丝生长生理的影响

[背景]L-氨基酸能够提供香菇生长发育的部分养分需求,利用外源添加氨基酸的方式对香菇生长基质进行优化,对于香菇产业的增产提质具有积极的发展意义.[目的]利用外源添加丙氨酸(Ala)、丝氨酸(Ser)和天冬酰胺(Asn)的方式改善培养基成分,并探究复配氨基酸促进香菇生长的可能代谢途径.[方法]在三因素三水平上,通过响应面...     

3-(2-萘基)-D-丙氨酸的制备

<正> 在生物界已发现40多种D-氨基酸,其生理作用正为人们逐渐认识。例如D-A.1-a—D-A.1a二肽是各种致病菌细胞壁肽聚糖的组成部分,D-丙氨酸是由丙氨酸消旋酶对L-丙氨酸消旋而来。如果丙氨酸消旋酶的活性被仰制,断绝了D-丙氨酸的来源,细菌     

L-丙氨酸厌氧发酵关键技术及产业化

传统氨基酸制造主要是通过化学合成或好氧发酵实现。相对于化学合成,微生物发酵可以实现以可再生资源为原料直接生产氨基酸,减少了对石油基原料的依赖,解决了化学合成高污染、高能耗等问题。好氧发酵具有生长快、产量高等特点,但好氧发酵中大量碳源用于细胞生长容易造成糖酸转化率低、能耗高等问题。厌氧发酵是近年来新出现的氨基酸生产模式,具有操作简单、无需通氧、糖酸转化率高容易接近理论最大值等优势。L-丙氨酸是国际上首个实现厌氧发酵产业化生产的氨基酸。本文以L-丙氨酸为例,综述了氨基酸厌氧发酵过程中的关键问题及其在产业化实施中的应用。未来,随着厌氧发酵关键技术在更多化合物生物制造技术中的突破,这种低成本、高效、低碳环保型发酵方式将会带来更大的经济价值和社会效益。     

[α]甘油磷酸氧化酶系的組成部份

(一) 在經徹底冲洗的兔骨骼肌製劑中,[L-α]甘油磷酸和琥珀酸的氧化彼此干涉。琥珀酸對[L-α]甘油磷酸氧化的抑制作用能因加入抑制琥珀酸脫氫酶的焦磷酸而解除。 (二) 當用細胞色素c作受體時[L-α]甘油磷酸,還原輔酶I和琥珀酸三者同時氧化時總氧化速度僅相當其中氧化速度最高者即還原輔酶I單獨氧化的速度。[L-α]甘油磷酸氧化酶系也因[2,3]二氫硫基丙醇的處理而失效。 (三) 當用[2,6]二氯酚靛酚作受體時[L-α]甘油磷酸和琥珀酸同時氧化時速度完全等於二底料單獨氧化時速度的和。[L-α]甘油磷酸的氧化不受苯代氨甲酸乙酯的影響。 (四) 本文結果說明[L-α]甘油磷酸的氧化不通過細胞色素b而通過中間因子和細胞色素c連接。     

pta基因敲除对L-色氨酸发酵的影响

[目的]探究pta基因缺失对大肠杆菌发酵生产L-色氨酸的影响.[方法]运用Red重组技术敲除pta基因,构建pta缺失株E.coli TRTH△pta.利用30 L发酵罐进行分批补料发酵试验,考察重组菌E.coliTRTHApta发酵0生产L-色氨酸过程中生物量、L-色氨酸产量、有机酸含量、发酵液中NH4+浓度及变化....     

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.