大肠杆菌—面包酵母种间耦合ATP再生系统中生物合成谷胱甘肽

利用混合悬浮培养的方法,构建了一个由重组大肠杆菌的谷胱甘肽生物合成酶系与面包酵母的糖酵解途径组成的ＡＴＰ再生系统,验证了该系统用于谷胱甘肽（ＧＳＨ）生物合成的可行性．研究了葡萄糖浓度、细胞量对耦合系统合成ＧＳＨ 能力的影响,讨论了所构建的ＡＴＰ再生系统中ＧＳＨ 合成能力较低的可能原因．     

提高耦合系统ATP再生效率促进谷胱甘肽合成的研究

利用重组Escherichia coliΔadd/ade(pBV03)和Saccharomyces cerevisiaeWSH2构建了一个生物合成谷胱甘肽(GSH)的种间耦合系统。在该耦合系统中,一方面,大肠杆菌腺苷脱氨酶和腺嘌呤脱氨酶的缺失完全切断了E.coliΔadd/ade(pBV03)中不可逆转化腺苷(Ado)生成次黄嘌呤(Hx)的途径;另一方面,利用脯氨酸限制性培养降低了酿酒酵母WSH2中ADE的活性,进一步降低了耦合系统中从Ado到Hx的不可逆转化。以上两方面大大降低了耦合系统中从Ado到Hx的不可逆转化,从而保证更多的底物Ado被S.cerevisiaeWSH2用于再生ATP,最终耦合系统中ATP再生的效率大大提高。反应6 h后,该耦合系统GSH的合成量达到13.68mmol/L,为对照的5.14倍。     

怎样选购网印彩色桌面出版系统

随着新千年的到来，在世界范围内，网印和成像工业正处于高速发展与充满挑战性的时代，国际网印及制像协会会长约翰·柯劳福德先生曾说过：“到２１世纪提供给商业印刷厂的原稿将 １００％为数字式。”正是由于计算机的应用及普及，促进了网印工业的发展。从传统工艺到ＤＴＰ（彩色桌面出版系统）的应用，再到ＣＴＰ技术，其功能越来越先进，而价格越来越低廉。虽说发展网印ＣＴＰ技术最终将取代ＤＴＰ，但在目前发展网印ＤＴＰ正是时候，因为网印ＤＴＰ系统已十分成熟，在短期内不会被淘汰，且升级方便。现就如何选购网印ＤＴＰ系统谈几点…     

酶解—膜分离耦合连续制备抗氧化性小分子透明质酸

目的：构建一种酶解—膜分离耦合的方法用来提高小分子透明质酸的生产效率。方法：利用酶生物反应罐与平板式聚醚砜超滤膜分离组件组成的连续式酶解—膜分离耦合反应体系。以膜通量、膜污染、透过液透明质酸质量浓度、产率为评价指标，系统地考察各因素对酶膜耦合体系内两种不同相对分子质量透明质酸分离效果的影响，并以产率为指标进一步通过正交试验优化酶膜耦合反应的工艺参数。结果：酶膜耦合反应体系制备小分子透明质酸的最优工艺参数为搅拌速度200 r/min、跨膜压力0.15 mPa、酶解时间4.0 h、加酶量5 g/100 g。该条件下可以快速制备并分离出两种不同相对分子质量（M_r）的小分子透明质酸，实现一步法同时制备M_r在1万～5万的低相对分子质量透明质酸（LMW-HA）和M_r＜3 000的透明质酸寡糖（O-HA），且这两种不同相对分子质量透明质酸均具有清除DPPH自由基和羟自由基的能力。结论：酶解—膜分离耦合法可以连续同步生产具有不同相对分子质量和一定抗氧化性的LMW-HA和O-HA。     

MANNICH反应改性聚合物鞣剂的表征及其应用研究

本文对经Ｍａｎｎｉｃｈ反应改性的Ｐ（ＡＡ－ＡＮ）聚合物鞣剂（ＡＳＦ）的基本性能进行了表征。通过对ＡＳＦ的ＩＲ、＾Ｈ－ＮＭＲ及＾１３Ｃ＝－ＮＭＲ谱图分析表明,在适宜条件下,Ｐ（ＡＡ－ＡＮ）的羧基α－Ｈ具有足够活性发生Ｍａｎｎｉｃｈ填上,还提高坏革的着色性能。该鞣剂的综合应用效果较好。     

阴离子聚丙烯酰胺（APAM）提高纸张干强度的研究

研究开发出一种新型引发系统，可以较准确地聚合所希望的平均相对分子质量大小的ＡＰＡＭ。并就ＡＰＡＭ的相对分子质量、取代度、添加量、添加位置、添加浓度、稳定性、浆料初始ｐＨ值、填料用量、硫酸铝用量等诸因素对ＡＰＡＭ增加晒图原纸和绘图纸的干强度的影响进行了较系统的试验，找出了利用ＡＰＡＭ增加纸张强度的最佳条件。     

大豆多肽的生理功能及应用(二)

３４大豆多肽与运动员体能的关系３４１运动员在剧烈运动时能量的消耗机理运动员在剧烈运动初期，首先消耗体内储存的三磷酸苷（ＡＴＰ）和肌酸磷酸（ＣＰ），然后分解糖原，经苯丙酸至乳酸，在这期间还产生ＡＴＰ又可作为能源。这一过程是在体内无氧状态下进行的，...     

精炼糖厂糖浆脱色与脱钙系统的树脂耦合再生应用研究

随着离子交换树脂系统在国内精炼糖厂的推广应用,树脂再生废液的高效处理和循环利用成为制糖行业的研究焦点.本文以离子交换树脂在精炼糖厂糖浆脱色和脱钙系统中的应用经验为基础,开展了利用树脂脱色系统的再生废液对树脂脱钙系统进行树脂再生的系统研究,以实现脱色与脱钙系统的树脂耦合再生,实现对树脂脱色系统再生废液的二次利用.结果表明...     

HACCP系统及其在火腿肠加工中的应用

ＨＡＣＣＰ系统及其在火腿肠加工中的应用生庆海吕加平骆承庠（东北农业大学食品科学系，哈尔滨１５００３０）１ＨＡＣＣＰ系统的原理ＨＡＣＣＰ，即危害分析关键控制点管理模式，是一个全面先进的卫生管理系统。传统上对食品的安全性检验主要通过感官评价及抽样测试的...     

新型乳液共聚浆料TP的研制与应用

通过乳液共聚反应，研制了一种粘度稳定，成膜性、退浆性能良好的乳液共聚浆料ＴＰ，对它进行生产应用的结果表明：该浆料在细号涤棉织物的经纱上浆中，与淀粉类浆料配合使用，可以大幅度减少ＰＶＡ浆料的用量和降低用浆成本，并能获得较理想的浆纱质量和织造效果。     

A novel ATP regeneration system using polyphosphate-AMP phosphotransferase and polyphosphate kinase

Polyphosphate-AMP phosphotransferase (PAP) and polyphosphate kinase (PPK) were used for designing a novel ATP regeneration system, named the PAP-PPK ATP regeneration system. PAP is an enzyme that catalyzes the phospho-conversion of AMP to ADP, and PPK catalyzes ATP formation from ADP. Both enzymes use inorganic polyphosphate [poly(P)] as a phosphate donor. In the PAP-PPK ATP regeneration system, ATP was continuously synthesized from AMP by the coupling reaction of PAP and PPK using poly(P). Poly(P) is a cheap material compared to acetyl phosphate, phosphoenol pyruvate and creatine phosphate, which are phosphate donors used for conventional ATP regeneration systems. To achieve efficient synthesis of ATP from AMP, an excessive amount of poly(P) should be added to the reaction solution because both PAP and PPK consume poly(P) as a phosphate donor. Using this ATP generation reaction, we constructed the PAP-PPK ATP regeneration system with acetyl-CoA synthase and succeeded in synthesizing acetyl-CoA from CoA, acetate and AMP. Since too much poly(P) may chelate MG2+ and inhibit enzyme activity, the Mg2+ concentration was optimized to 24 mM in the presence of 30 mM poly(P) in the reaction. In this reaction, ATP was regenerated 39.8 times from AMP, and 99.5% of CoA was converted to acetyl-CoA. In addition, since the PAP-PPK ATP regeneration system can regenerate GTP from GMP, it could also be used as a GTP regeneration system.     

Thermostable ATP regeneration system using polyphosphate kinase from Thermosynechococcus elongatus BP-1 for D-amino acid dipeptide synthesis

D-alanine-D-alanine ligase from Thermotoga maritima ATCC 43589 (TmDdl) was a useful biocatalyst for synthesizing D-amino acid dipeptides. TmDdl showed a broad substrate specificity at a high temperature; however, ATP was required for its reaction. One of the methods for an effective ATP supply was the coupling reaction with an ATP regeneration system. However, ATP regeneration systems consisted of enzymes from mesophiles and were difficult to operate at high temperatures. Therefore, an ATP regeneration system that could be used at high temperatures was desired to utilize TmDdl for the effective production of D-amino acid dipeptides. To establish a thermostable ATP regeneration system, polyphosphate kinase from a thermophile, Thermosynechococcus elongatus BP-1 (TePpk), was characterized. TePpk showed thermostability up to 70 degrees C; therefore, it was considered that a thermostable ATP regeneration system could be established using TePpk. In the coupling reaction with purified TmDdl and TePpk at 60 degrees C, the amount of ATP required for D-alanyl-D-alanine synthesis could be reduced to 1% of the theoretical amount required when there was no ATP regeneration. When the coupling reaction was applied to a resting cell reaction, ATP was regenerated from an adenosine scaffold in the cell, and D-alanyl-D-alanine was successfully synthesized in the maximum yield of 80% (mol/mol) without the addition of ATP. Thus, an effective synthesis of D-amino acid dipepitides was achieved using the thermostable ATP regeneration system.     

Theoretical investigation of fructose 1,6-diphosphate production and simultaneous ATP regeneration by conjugated enzymes in an ultrafiltration hollow-fiber reactor

The performance of an ultrafiltration hollow-fiber reactor, in which enzymatic synthesis of fructose 1,6-diphosphate (FDP) from glucose and enzymatic ATP regeneration are performed simultaneously, was analyzed theoretically. The reaction system consists of three-step synthetic reactions catalyzed by glucokinase (GK), phosphoglucose isomerase and phosphofructokinase, and the ATP regeneration reaction catalyzed by acetate kinase. Based on a simple analytical model developed previously in which the liquid flowing in a tube was assumed to be plug flow and the radial concentration gradients in the tubes and shell side space were both neglected, a computer program was developed to calculate the concentration profiles of all the components along the flow direction in the tubes and shell side space of the reactor. From the FDP concentrations at the reactor outlet calculated under various operational conditions, reactor performances such as the FDP yield and the ATP recycle number were determined. The calculation showed the interesting phenomenon that under some conditions the FDP yield was higher when GK concentration was lower.     

Experimental investigation of fructose 1,6-diphosphate production and simultaneous ATP regeneration by conjugated enzymes in an ultrafiltration hollow-fiber reactor

The enzymatic synthesis of fructose 1,6-diphosphate (FDP) from glucose and the enzymatic ATP regeneration were performed simultaneously in an ultrafiltration hollow-fiber reactor using both the purified enzymes and the crude cell extract of Bacillus stearothermophilus. The process consisted of the three-step synthetic reactions catalyzed by glucokinase, phosphoglucose isomerase and phosphofructokinase, and the ATP regeneration reaction catalyzed by acetate kinase. The experimental results of the yield and the recycle number agreed well with the theoretical predictions calculated using a computer program developed in our preceding study. This proved the validity of this computer program for predicting or analyzing the reactor performance.     

Catharanthine oxidation in flavin mononucleotide-mediated catharanthine-vindoline coupling reaction for synthesis of dimeric indole alkaloids under near-ultraviolet light

A reaction model for the flavin mononucleotide-mediated coupling of catharanthine (C) and vindoline (V) under near-ultraviolet light was established based on the results of experiments on the effects of various physical and chemical factors on the disappearance of C and V, and the synthesis of the product, a dihydropyridinium intermediate (IM). The following events were deduced to occur. (i) C is oxidized in the presence of FMN and oxygen under near-ultraviolet light (C(OX1)). (ii) C(OX1) then couples with V to form IM. Degradation of C occurs simultaneously with its specific oxidation, as a result of which a part of the C is converted into the product (C*) which is incapable of coupling with V. When a reaction in which C(OX1) is further oxidized to another form (C(OX2)) is added and the counterpart for the coupling with V is changed to C(OX2) from C(OX1), the reaction model more appropriately describes the exponential increase in the product, IM, that occurs in the early stage of the coupling reaction. (iii) The degradation rate of IM is much greater after C has been consumed than before its disappearance. Using this reaction model, the coupling reactions under basal and optimized conditions were simulated and the results showed a good fit with the experimental values under both conditions. The kinetic study suggests that manganese ion (Mn2+) stimulates the binding of C(OX2) with V in addition to suppressing the degradation of C, resulting in an increased yield of IM. Mn2+ thus appears to be an important factor in the coupling reaction, in which it plays two different roles.     

烟草DNA的提取与SRAP反应体系的建立

以10个烟草栽培品种为试验材料,研究了烟草DNA的提取方法以及对建立烟草SRAP-PCR反应体系的影响因子设置梯度实验,筛选和建立可扩增多态性高、重复性好、带型清晰的最佳SRAP-PCR反应条件:在25μL的反应体系中,MgCl22.0mmol、dNTP200μmol,上下引物各30ng、DNA模板40ng、DNA聚合酶1.5U,扩增程序为:在94℃预变性5min,反应前5个循环在94℃1min,33℃1min,72℃1min条件下运行;随后的30个循环复性温度提高到53℃,最后72℃延伸5min。本文还讨论了不同分子标记在烟草中应用的优缺点以及SRAP分子标记在烟草上的应用前景,提出了应用SRAP分子标记构建烟草遗传图谱的可行性。      

蒽酮比色法快速测定大麦叶片中可溶性糖含量的优化

以大麦嫩苗鲜叶为试验材料,对经典蒽酮比色法反应体系中蒽酮及硫酸的用量、反应温度、反应时间、样品提取时间以及叶片取样部位等条件进行优化研究。结果表明,对蒽酮硫酸反应体系进行优化后的条件为:最佳蒽酮用量为100μL、浓硫酸为1 000μL;显色反应温度为100℃,最佳反应时间7 min;样品提取时间以沸水浴10 min为宜;大麦叶片取样部位以倒二叶顶部较为合适。该方法操作简单、快速、实用性强,可为植物样品可溶性糖指标快速筛选提供有效的参考价值。     

Characterization of the Maillard reaction in bread crisps

Maillard reaction (MR) is one of the main chemical event occurring during baking. To study the reaction in bakery products, a dry model system is more useful than an aqueous one. In this work, the effects of formulation and processing conditions in a crisp bread system were investigated to test the effects of different additives on both the overall reaction and the formation of MR products such as 5-hydroxymethyl-2-furaldehyde (HMF) and acrylamide. Cylindrical dough made up of flour, water and yeast was baked at 180 °C for 35 min and the slices were toasted at different times/temperatures combinations. Browning and water content were monitored along with the kinetic of formation of chemical indicators such as HMF and acrylamide also calculating rate constants and activation energy. These parameters were also monitored in systems added with glycine and asparaginase. During toasting water content follows an exponential trend, being the rate of water loss faster in the initial stage of toasting and at higher temperature. Browning was more intense when toasting at higher temperature and a linear correlations between browning (ΔL*, ΔE*), HMF and acrylamide concentration were observed when toasting at 180 °C. HMF and acrylamide content increased with the toasting time and temperature. Their concentrations were strongly dependent on the water content of the final product, and both the addition of glycine and asparaginase are effective in reducing acrylamide content. The addition of glycine enhanced the browning of toasted bread, and slightly increased HMF content at any toasting temperature. The system characterized in this work represents a suitable tool to study the development of the MR in dry systems.     

微波加热缬氨酸和葡萄糖的棕化反应

研究了微波加热下pH值、反应时间、溶剂配比对缬氨酸与葡萄糖的棕化产物反应深度的影响,以及微波加热和普通加热的棕化产物的差异,并进行了棕化产物的卷烟加香试验及其醚溶性成分的分析。结果表明:①微波能加速棕化反应进程,在相同反应时间内微波反应产物的一些主要成分含量要大于普通加热产物;②温度对棕化反应影响大于加热方式;③相同体系,普通加热和微波加热棕化产物成分基本相同,只是在含量上有差别;④体系的pH值对微波棕化反应进程及反应产物都有较大影响,酸性和碱性环境都能加速反应进程;⑤微波加热的缬氨酸与葡萄糖产物中共鉴定出5种重要的吡嗪类化合物和1种呋喃类化合物,没有鉴定出醛类、吡咯类等常见的普通棕化反应产物;⑥在微波加热,pH6·35,反应时间30min,溶剂为丙二醇-水(1∶1体积比)条件下,缬氨酸与葡萄糖的棕化反应产物加香效果较好。