共查询到19条相似文献,搜索用时 140 毫秒
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通过环境压力筛选获得了一株耐受30 g/L丙酸的产酸丙酸杆菌菌株(Propionibacterium acidipropionici WY320),降低了发酵过程中丙酸的反馈抑制作用,采用正交实验设计优化了发酵培养基. 结果表明,发酵培养基最适的玉米浆、酵母膏和(NH4)2SO4浓度分别为60, 10和7.5 g/L. 该条件下,摇瓶培养耐酸菌株的发酵周期为240 h,丙酸产量为49.35 g/L,较优化前提高72.98%,产率为0.21 g/(L×h); 5 L发酵罐培养的发酵周期为168 h,丙酸产量达51.96 g/L,产率为0.31 g/(L×h),较摇瓶培养提高47.62%,优于文献报道水平. 相似文献
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建立Elson-Morgan法测定胶囊剂中D-氨基葡萄糖盐酸盐的含量。方法 样品中D-氨基葡萄糖盐酸盐用水溶解,与乙酰丙酮、对二甲氨基苯甲醛试液显色之后,以试剂空白溶液为参比,以D-盐酸氨基葡萄糖为对照品,在525 nm波长处比色测定。D-氨基葡萄糖盐酸盐含量在20. 26~121. 56μg范围内,线性关系良好。加标回收率为101. 8%~103. 4%,精密度RSD为0. 10%,重复性RSD为0. 90%。本方法简便准确可靠,可用于胶囊剂中D-氨基葡萄糖盐酸盐含量的测定。 相似文献
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以甲壳素为原料,通过正交试验法研究制备D-氨基葡萄糖盐酸盐工艺的最优化反应条件。即甲壳素酸水解制备D-氨基葡萄糖盐酸盐的最优条件为:27%盐酸,甲壳素与盐酸质量比为1∶7,95℃下水解5 h,此条件下D-氨基葡萄糖盐酸盐为D-氨基葡萄糖盐酸盐,优化得到的D-氨基葡萄糖盐酸盐提取工艺稳定可行,为工业生产提供了理论基础。 相似文献
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通过对补料时间、方式和补料液浓度变化(特别是补加氮源)对D-核糖发酵过程影响,确定了D-核糖发酵的补料工艺。按此工艺条件,发酵的时间为72 h,D-核糖的产量93.83 g/L,剩余葡萄糖浓度为4 g/L,转化率为0.284 3 g/g,生产强度为1.303 g/(L.h)。与不补料相比,D-核糖产量提高了95.9%。 相似文献
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为了降低生物法制备甘露醇的成本,以假肠膜明串珠菌Leuconostoc pseudomesenteroides G123为研究对象,对培养基中的氮源、葡萄糖与果糖比例和pH调控过程进行了优化,提高了果糖转化率和甘露醇产量。5L发酵罐中结果显示:采用2g/L的酵母粉作为单一氮源,葡萄糖和果糖的比例为0.35:1,初始pH值7.5,发酵过程中保持pH值不低于4.5,甘露醇产量可达57.24g/L,甘露醇对果糖的转化率为83.2%。该过程副产D-乳酸20.32g/L,其光学纯度达99.9%,具有回收价值,甘露醇与D-乳酸对糖总转化率为89.38%,有助于降低生物法制备甘露醇的成本。 相似文献
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以(NH4)2SO4为底物氮源,采用平板变色圈法从土壤中分离筛选出一株2-酮基-D-葡萄糖酸生产菌株Serratia sp. FMME043,对其碳源、氮源、无机源和摇瓶类型等产酸条件进行优化,确定以(NH4)2SO4为氮源的摇瓶产酸最佳条件为葡萄糖180 g/L, (NH4)2SO4 2.0 g/L, KH2PO4 1 g/L,在初始pH 7.0及750 mL双刺摇瓶装液量10%、培养温度30℃、摇床转速200 r/min条件下发酵48 h,2-酮基-D-葡萄糖酸产量达169.5 g/L,得率为0.87 mol/mol,并在7 L发酵罐中进行了验证. 相似文献
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从土壤中筛选得到一株可以选择性氧化2,5-二甲基吡嗪生成5-甲基吡嗪-2-羧酸的产单加氧酶菌株ZJB-LLJ,经过生理生化鉴定及16S rDNA序列分析确定为恶臭假单胞菌。并对其转化2,5-二甲基吡嗪产5-甲基吡嗪-2-羧酸的条件进行了优化,结果表明,在500mL摇瓶中装液100mL、温度为30℃、pH值为7~8、以对二甲苯为唯一碳源、诱导培养12h后添加底物的条件下,产物积累量最大;采用分批流加的方式积累产物较快,转化528h后5-甲基吡嗪-2-羧酸浓度达20.41g·L-1,产率达到75.6%。 相似文献
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Schlegel MK Peritz AE Kittigowittana K Zhang L Meggers E 《Chembiochem : a European journal of chemical biology》2007,8(8):927-932
Glycol nucleic acid (GNA) has an acyclic backbone of propylene glycol nucleosides that are connected by phosphodiester bonds. This paper characterizes the duplex-formation properties of this simplified nucleic acid. Although single and multiple GNA nucleotides are highly destabilizing if incorporated into DNA duplexes, the two enantiomeric oligomers (S)-GNA and (R)-GNA form antiparallel homoduplexes that are thermally and thermodynamically significantly more stable than analogous duplexes of DNA and RNA. The salt-dependence and Watson-Crick-pairing fidelity of GNA duplexes are similar to those of DNA duplexes, but, apparently, the 2'-deoxyribonucleotide and the propylene glycol backbones are not compatible with each other. This conclusion is further supported by cross-pairing experiments. Accordingly, both (S)- and (R)-GNA strands do not generally pair with DNA. However, (S)-GNA, but not (R)-GNA, forms stable heteroduplexes with RNA in sequences that are low in G:C content. Altogether, the high stability and fidelity of GNA duplex formation in combination with the economical accessibility of propylene glycol building blocks for oligonucleotide synthesis render GNA an attractive candidate for the design of self-assembling materials. They further suggest that GNA could be considered as a potential candidate for a predecessor of RNA during the evolution of life on Earth. 相似文献
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D. Seinsche K. Taraz H. Budzikiewicz D. Gondol 《Advanced Synthesis \u0026amp; Catalysis》1993,335(2):157-168
New Pyoverdin Siderophores from Pseudomonas putida C Four new pyoverdins (C 2A, C 2B, C 3A, C 3B) were isolated from cultures of Pseudomonas putida C. Their structures were elucidated by chemical and spectroscopic methods. The compounds consist of a chromophore – (1S)-5-amino-2,3-dihydro-8,9-dihydroxy-1H-pyrimido [1,2-a]quinoline-1-carboxylic acid – substituted at the amino group with a dicarboxylic acid or its amide. The carboxyl group of the chromophore is amidically bound to the N-terminus of L-Asp-D-[N5-hydroxy-N5-(D-β-hydroxybutyryl)] Orn-D-Dab-L-Thr-Gly-D-Ser-L-Ser-L-threo-β-hydroxy-Asp-L-Thr. The four pyoverdins differ only in the nature of the dicarboxylic acid (amide), viz. L-malamoyl- (C 2A), succinamoyl- (C 2B), L-3-carboxy-2-hydroxypropanoyl- (C 3A) or 3-carboxypropanoyl (C 3B) residue. The hydroxamate function consists of N5-hydroxy-Orn and β-hydroxybutyric acid, a structural unit which has been encountered for the first time in a pyoverdin. 相似文献
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以D-氨基葡萄糖盐酸盐与对甲氧基苯甲醛、对甲基苯甲醛反应合成了两种新的D-氨基葡萄糖席夫碱(对甲氧基苯甲醛缩D-氨基葡萄糖席夫碱、对甲基苯甲醛缩D-氨基葡萄糖席夫碱),收率分别为67.9%、74.6%。使用UV1、HNMR和IR对产物进行了结构表征。测试了两种席夫碱甲醇饱和溶液对香蕉炭疽病菌、芒果炭疽病菌、芒果蒂腐病菌、芒果焦腐病菌、番木瓜炭疽病菌等植物病原真菌的抑菌性能。结果表明,对甲氧基苯甲醛缩D-氨基葡萄糖席夫碱对香蕉炭疽病菌、芒果蒂腐病菌、芒果焦腐病菌具有很强的抑菌活性,对甲基苯甲醛缩D-氨基葡萄糖席夫碱对香蕉炭疽病菌、芒果炭疽病菌具有很强的抑菌活性。 相似文献
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1,2,4-丁三醇(1,2,4-butanetriol, BT)是一种重要的有机合成中间体。通过克隆表达恶臭假单胞菌(Pseudomonas putida ATCC12633)2-酮酸脱羧酶(mdlC)和新月柄杆菌(Caulobacter crescentus CB15)D-木糖脱氢酶(xdh),敲除木糖利用和D-1,2,4-丁三醇合成中间代谢物分解途径中关键基因木糖异构酶(xylA)和2-酮酸醛缩酶(yjhH和yagE),重构大肠杆菌代谢网络,得到了能够将D-木糖转化为D-1,2,4-丁三醇的重组菌株。考察了温度、装液量、pH控制等条件对重组菌株合成D-1,2,4-丁三醇的影响,在适宜条件下发酵36 h后D-1,2,4-丁三醇产量达到3.96 g·L-1。探讨了葡萄糖利用与丁三醇合成的关系,通过敲除编码酶IICBGlc的ptsG基因改造重组菌株的磷酸烯醇式丙酮酸葡萄糖转移酶(phosphoenolpyruvate: sugar phosphotransferase system, PTS)系统,菌株可以在利用葡萄糖生长的同时进行木糖的转化,具有更高的合成能力。 相似文献