Zn2+对制麦的影响及作用机理的研究

研究了制麦过程中添Zn2+加对制麦影响及Zn2+作用机理。发现Zn2+抑制麦芽苹果酸脱氢酶(MDH)活性,在添加0.3mmol/L、1.2mmol/L、2.1mmol/L Zn2+的实验组中MDH活性均受到抑制。Zn2+通过抑制MDH活性抑制麦芽呼吸作用,减少麦芽中糖的消耗,从而降低了制麦损失;添加0.3mmol/L Zn2+没有降低呼吸损失反而有促进作用,1.2mmol/L、2.1mmol/L Zn2+都能降低制麦损失,且Zn2+浓度越高抑制作用越明显。同时研究了Zn2+对麦芽几项重要品质的影响,结果表明添加Zn2+会小幅降低麦芽的蛋白溶解度及糖化力,但麦芽的浸出率有所提高。     

鱼精蛋白对黑曲霉细胞内的琥珀酸脱氢酶和苹果酸脱氢酶的影响

鱼精蛋白是一种多聚阳离子天然肽类,它是一种碱性蛋白质。为探讨其抑菌作用,我们研究了鱼精蛋白对黑曲霉细胞内的琥珀酸脱氢酶和苹果酸脱氢酶的影响。结果表明,鱼精蛋白具有抑制琥珀酸脱氢酶和苹果酸脱氢酶的活性(p<0.01),但效果低于纳他霉素。提示鱼精蛋白用作食品防腐剂具有很大的潜力。     

猪心肌苹果酸脱氢酶的制备及应用

设计并优化了从猪心中提取高纯度苹果酸脱氢酶的技术路线,采用组织破碎、二度硫酸铵盐析、DEAE Sepharose F.F.离子交换层析、Phenyl Sepharose 6 F.F.疏水层析及Sephadex G-75 Fine凝胶过滤等方法进行分离纯化,苹果酸脱氢酶比酶活达1 212.97 U/mg,纯化倍数达122.64倍,酶活力收率为53.64%.Sephadex G-75 Fine凝胶过滤和SDS-PAGE电泳结果显示纯化的苹果酸脱氢酶相对分子质量约为 69 000 ,含有2个亚基,每个亚基的相对分子质量约为 34 000 .以制备的苹果酸脱氢酶和谷草转氨酶配成双酶反应体系,对葡萄酒中L-苹果酸的含量进行了测定;通过标准样品和葡萄酒样品精密度及回收率(93.2%～104%)实验.     

猪心苹果酸脱氢酶的分离纯化及性质

采用组织破碎,二度硫酸铵盐析,DEAE Sepharose F.F.离子交换层析及Sephadex G-75 Fine凝胶过滤等纯化方法,从猪心中提取得到了苹果酸脱氢酶.提取纯化的苹果酸脱氢酶经SDS-PAGE测定显示为单一条带,相对分子质量为34000.酶活回收率为57.99%,最适pH为8.0,最适温度为50℃.     

鸭心苹果酸脱氢酶功能基团的研究

分别用对氯汞苯甲酸、苯甲基磺酰氟、N-溴代琥珀酰亚胺、琥珀酸酐、乙酰丙酮、溴代乙酸、N-乙酰咪唑、二巯基苏糖醇、氯胺-T等化学修饰剂对鸭心苹果酸脱氢酶进行修饰。结果表明：半胱氨酸巯基、色氨酸侧链吲哚基和丝氨酸羟基是鸭心细胞质苹果酸脱氢酶和线粒体苹果酸脱氢酶发挥活性的必需基团;而甲硫氨酸的硫醚基、组氨酸的咪唑基、精氨酸胍基、二硫键、酪氨酸的酚羟基、赖氨酸的ε-氨基与鸭心苹果酸脱氢酶活性不直接相关,不是酶活性中心的必需基团。     

绿豆中苹果酸脱氢酶的性质及生物进化的研究

首次报道了豆科植物来源的苹果酸脱氢酶——绿豆苹果酸脱氢酶的纯化及表征。前期实验结果已于2005年发表于JournalofFoodBiochemistry,本文对该绿豆中苹果酸脱氢酶的性质及生物进化等做了进一步研究。结果显示:苹果酸脱氢酶对底物草酰乙酸的米氏常数为112μmol/L。酶活性受金属离子效应物影响,其中KCl对酶有激活作用,CaCl2和MgCl2对酶活影响不大,ZnCl2、PbCl2和CuSO4表现出不同程度的抑制酶活作用。锌离子对该酶的作用属于非竞争性抑制。通过Edman降解法测定其N-氨基酸序列为N-ASEPGPERKVAVL-GAAGGIG-20,与其它植物来源的苹果酸脱氢酶的同源性分别达到75%～95%。采用CLUSTALW多序列比对软件产生的进化树结构,与绿豆亲缘关系由近至远依次是大豆、苹果树、西瓜、土豆、芥菜、苜蓿、番茄。     

制麦对大麦中β-葡聚糖酶和植酸酶活性的影响

通过三因素(浸麦温度、湿度、发芽温度)两水平析因试验，研究了制麦过程对裸麦和芒麦中的β-葡聚糖和植酸含量的影响。在高温(48℃)下浸麦时，麦芽的β-葡聚糖总量变化很小，而浸麦温度(15℃)较低时，β-葡聚糖总量显著下降。温度为38℃时，对于不可溶β-葡聚糖来讲，这一趋势就更为明显。通过麦芽中的β-葡聚糖酶活性分析发现，浸麦温度为15℃，活性显著增加，而浸麦温度为48℃时，活性增加缓慢。另外两个因素对结果影响较小，主要是因为浸麦温度是对β-葡聚糖和β-葡聚糖酶活最重要的影响因素。当在100℃提取β-葡聚糖时，提取量较大，浸麦温度对提取量的影响大于提取温度。浸麦温度为15℃时的β-葡聚糖平均分子量要低于浸麦温度为48℃时。本试验设计的的因素水平对植酸的简介和植酸酶的活性没有多大影响。结果显示，既然本试验设计的参数对植酸酶活性几乎没有影响，而对β-葡聚糖酶活影响很大，那么就有可能对酶进行有选择性的控制。     

大肠杆菌苹果酸脱氢酶基因mdh的克隆、高效表达及酶学性质

以大肠杆菌基因组DNA为模板,扩增得到苹果酸脱氢酶(mdh)编码基因mdh,构建了重组菌pET-28a-mdh/BL21并成功表达了mdh,大小约36 000。选用Ni柱亲和层析法纯化具有活性的苹果酸脱氢酶(mdh),纯化后比酶活达到112.5 U/mg,纯化倍数达2.62倍,回收率为59%。并对该酶的酶学性质进行了初步研究,其中反应最适pH值为6.0,在pH值2.0~6.0范围内稳定;反应最适温度为37℃,在42℃以下酶的稳定性较好。K+对酶有明显的激活作用,Cu2+对酶有抑制作用,Hg2+和Zn2+对酶有很强的抑制作用。醇类对酶的活力影响不大,丙三醇可显著提高酶的热稳定性。酶动力学参数以草酰乙酸为底物的Km为0.235 mmol/L,Vmax为0.47μmol/(L.min)。     

生物制麦中白地霉的筛选及其特性的研究

以甘啤3号大麦为原料,从中分离得到了2株生长能力较强的菌株,通过对该菌产生的β－葡聚糖酶、木聚糖酶、纤维素酶和糖化酶的酶活情况进行研究及生理生化鉴定得出该菌株为白地霉,分别为白地霉GQG28．1和白地霉GQG28．2。对筛选到的白地霉GQG28生长特性的初步研究表明,该菌最适生长温度为25℃,生长温度范围为5℃～37℃,其最适生长pH5．6,最低生长pH值为3．2,最高生长pH值为11．0,利用该白地霉制得麦芽综合指标为206．15,所制麦芽糖化力为308．5WK、α-氨基氮为186mg／100g、浸出物相对质量分数为87．1％。     

微生物中苹果酸脱氢酶研究现状及展望

苹果酸脱氢酶（MDH）EC 1.1.1.37是一类广泛存在于自然界生物体内的氧化还原酶,主要参与三羧酸循环（TCA）、乙醛酸循环、苹果酸-天冬氨酸循环等代谢途径。该酶可催化草酰乙酸和苹果酸之间的可逆转化,是细胞中心代谢通路中的关键酶之一。MDH广泛应用于心肌梗塞、急性实质性肝损伤、肝癌、肺癌的早期诊断,是常用的临床诊断用酶,并在生物制药、化工检测等领域也具有广泛市场需求。该文综述了微生物中MDH的蛋白结构、催化机制以及活性调节,并对其酶学性质、医疗诊断及免疫领域的应用、工业领域的应用以及生产方面,阐述了苹果酸脱氢酶的研究进展,以期为苹果酸脱氢酶的进一步开发和利用提供参考。     

Purification and characterization of malate dehydrogenase from Corynebacterium glutamicum

The malate dehydrogenase (MDH) (EC 1.1.1.37) from Corynebacterium glutamicum (Brevibacterium flavum) ATCC14067 was purified to homogeneity. Its amino-terminal sequence (residues 1 to 8) matched the sequence (residues 2 to 9) of the MDH from C. glutamicum (GenBank accession no. CAC83073). The molecular mass of the native enzyme was 130 kDa. The protein was a homotetramer, with a 33-kDa subunit molecular mass. The enzyme was almost equally active both for NADU and NADPH as coenzyme on the bases of the k(cat) values at pH 6.5 which is the optimum pH for the both coenzymes. Plotting of the logarithms of the 1/Km, k(cat), and k(cat)/K(m) values with respect to oxalacetate against pH lead to speculation that imidazolium is possibly a functional group in the active center of the enzyme. Citrate activated the enzyme in the oxidation of malate to oxalacetate and inhibited it in the reverse reaction.     

大麦发芽过程中蛋白质组的变化研究

通过双向电泳技术监测大麦发芽过程中水溶蛋白质组的变化,明确大麦发芽过程中蛋白质组的变化规律,为麦芽制造提供一定理论依据。以澳麦\     

不同添加物对大麦发芽过程中热稳定蛋白含量的影响

为了解发芽过程中热稳定蛋白动态变化趋势,以澳麦为原料,模拟工业制麦条件,系统分析了麦芽制备过程中热稳定蛋白分布变化。通过在浸麦最后一天添加Mg2+、K+、赤霉素(GA3)调节蛋白酶酶活及分解。采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)电泳和考马斯亮蓝法(Bradford法),研究添加金属离子及赤霉素后热稳定蛋白分布及含量。结果表明,麦芽中热稳定蛋白分子质量主要分布在约40 ku和10 ku两个区域。经制麦后,40 ku分子质量蛋白质含量增加,10 ku附近蛋白质含量变化不明显。Mg2+和赤霉素添加降低了热稳定蛋白含量,K+有利于热稳定蛋白含量增加。     

掺杂Fe~(3+)和Zn~(2+)纳米二氧化钛薄膜光催化降解制革废水的试验研究

以掺杂Fe3+和Zn2+的纳米TiO2薄膜作为光催化剂,以自然光为光源,石英砂为载体。初始pH为6.7的条件下,选取热处理温度、Fe3+掺杂比、Zn2+掺杂比、H2O2投加比4个因素设计正交试验,对经絮凝沉淀预处理后的制革废水进行处理,以CODcr和色度去除率为评价指标,探讨了这些因素对CODcr和色度的去除率影响。在最佳条件下就掺杂离子对TiO2薄膜吸收光波段红移的影响和光催化处理后废水可生化性的影响,做了进一步研究。     

Effect of cold shock on the enhancement of β‐amylase activity during malting and malt processability for a red sorghum intended for brewing use

The low β‐amylase activity of sorghum malt is a major concern when malts are intended for use in brewing. Several studies have shown that the germination temperature plays an important role in β‐amylase synthesis. In this study, the cold shock treatment was envisioned as a means of improving β‐amylase synthesis during red sorghum malting. The results show that, when a high‐frequency decrease in the germination temperature is used, the obtained malt exhibits a significantly increased β‐amylase activity. This study shows that this increase is not sufficient to consider cold shock as a means of improving β‐amylase activity for red sorghum brewing use, as the processabilty of the malts is unsatisfactory. Copyright © 2015 The Institute of Brewing & Distilling     

Effects of malting on β‐glucanase and phytase activity in barley grain

The effects of malting on β‐glucan and phytate were investigated in one naked and one covered barley by a full factorial experiment with three factors (steeping temperature, moisture content and germination temperature) each with two levels. Analysis of total content of β‐glucan in the malted samples showed small changes after steeping at the high temperature (48 °C), while steeping at the lower temperature (15 °C) gave a significantly lower content. This trend was even stronger for β‐glucan unextractable at 38 °C. Analysis of the activity of β‐glucanase for the samples steeped at 15 °C showed a strong increase over the time of germination, while those steeped at 48 °C had a much slower development. The other two factors influenced the outcome to a small extent, mainly because the steeping temperature was the most important factor overall where any changes in β‐glucan and β‐glucanase were observed. When β‐glucan was extracted at 100 °C, a larger yield was obtained, and this was influenced by the steeping temperature in a much stronger way than for β‐glucan extracted at 38 °C. Determination of average molecular weight for β‐glucan extracted at 100 °C gave a lower value for samples steeped at 15 than at 48 °C. The design did not have any large effects on phytate degradation and phytase activity. However, it indicated that selective control of the enzymes might be possible, since phytase activity was barely affected by the parameters studied, while β‐glucanase was heavily affected. © 2002 Society of Chemical Industry     

Effect of malting on antioxidant capacity and vitamin E content in different barley genotypes

Unprocessed barley is known to contain relatively high levels of antioxidants, which play a critical role in human health and the preservation of food and drink products. However, there are limited data on how the antioxidant levels in barley are affected by malting, and whether the level of antioxidants in the processed malt differs between barley varieties. This study aimed to determine the levels of individual vitamin E isomers, total vitamin E content and total antioxidant capacity before, during and after malting in 12 covered and two hulless barley genotypes. Vitamin E content and antioxidant capacity were determined by high‐performance liquid chromatography (HPLC) and ability to scavenge DPPH radicals, respectively. The vitamin E content of most genotypes was reduced after steeping, germination and kilning compared with the unprocessed samples. However, the antioxidant capacity in the malt was higher than in the unprocessed samples for the majority of the genotypes. While there was variation in the percentage change in antioxidant capacity between varieties, the antioxidant capacity of samples after malting was directly correlated with their antioxidant capacity before processing (r = 0.9, n = 14, p < 0.05). These results indicate that barley varieties that have higher antioxidant capacity at harvest retain their antioxidants after malting. Thus, these varieties are likely to be the most suitable for producing malts with the added health benefits and anti‐spoiling properties associated with greater antioxidant content. Copyright © 2015 The Institute of Brewing & Distilling     

2-Acetylindan-1,3-dione and its Cu(2+) and Zn(2+) complexes as promising sunscreen agents

In continuation of a previous spectroscopic and quantum chemical study on 2-acetylindan-1,3-dione (2AID), the spectral properties and photostability of 2AID and its Cu(2+) and Zn(2+) complexes in different solvents are reported. Comparison is made with the photostability of two commercially available sunscreens: benzophenone-3 and octylmethoxycinnamate. 2AID exhibits a higher photostability, high molar absorption coefficient (42 000 m(-1) cm(-1)) at lambda(max) and broad-spectrum UV-protection properties. The hypothesis that the strong intramolecular H-bonding is responsible for the higher photostability was confirmed by studying the photodegradation upon irradiation with UV light of 2AID in hydrogen bond-breaking solvent, DMSO. The data obtained show that 2AID undergoes rapid degradation in this solvent. It is found that Cu(2+) and Zn(2+)-2AID complexes show higher photostability in DMSO than 2AID itself.