浅谈食用酒精生产工艺中挥发性杂质的控制方法

勾兑白酒的质量与食用酒精的质量息息相关,简述了食用酒精质量对勾兑白酒口感的重要性,食用酒精对提高勾兑白酒质量的作用,以及生产工艺中挥发性杂质的组成及来源,阐述了如何在生产工艺环节中控制挥发性杂质含量的技术手段。     

Red Algal Bromophenols as Glucose 6-Phosphate Dehydrogenase Inhibitors

Five bromophenols isolated from three Rhodomelaceae algae (Laurencia nipponica, Polysiphonia morrowii, Odonthalia corymbifera) showed inhibitory effects against glucose 6-phosphate dehydrogenase (G6PD). Among them, the symmetric bromophenol dimer (5) showed the highest inhibitory activity against G6PD.     

黑穗醋栗果实生长发育过程中抗坏血酸含量 及相关酶活性的变化

【目的】 研究不同品种不同生长时期黑穗醋栗果实内抗坏血酸（AsA）含量及其合成代谢过程中相关酶活性的变化,以明确果实生长发育过程中AsA含量与代谢合成相关酶之间的关系,为全面揭示黑穗醋栗果实AsA积累规律提供理论依据。【方法】 以3个不同黑穗醋栗品种（‘亚德’‘布劳德’和‘黑丰’）为试材,测定果实在幼果期、膨大期、半转色期、转色期和成熟期时还原型抗坏血酸（AsA）、氧化型抗坏血酸（DHA）、还原型谷胱甘肽（GSH）和氧化型谷胱甘肽（GSSG）含量以及AsA合成与代谢相关酶活性。【结果】 不同品种黑穗醋栗果实大小、AsA含量以及AsA相关代谢物水平存在明显的多样性。其中‘亚德’单果重最大,为1.97 g。果实生长发育过程中,总抗坏血酸（T-AsA）和AsA含量在3个品种中变化趋势一致,均在幼果期含量最高,其中‘亚德’幼果期果实中AsA含量最高,为83.17 μmol·g ^-1 FW,随着果实的生长迅速下降,在成熟期降至21.28 μmol·g ^-1 FW;3个品种果实中GSH和T-GSH含量随着果实发育呈升高趋势,但不同品种升高时期或增加幅度不同;GSSG含量在不同品种间存在较大差异,成熟果中‘黑丰’含量最低,为0.008 μmol·g ^-1 FW,仅为‘亚德’的10.2%。AsA-GSH循环再生代谢中,脱氢抗坏血酸还原酶（DHAR）和单脱氢抗坏血酸还原酶（MDHAR）活性在果实膨大期达到最高,成熟期降至最低,其中‘布劳德’果实中DHAR和MDHAR活性略高于‘亚德’和‘黑丰’;谷胱甘肽还原酶（GR）活性在幼果期最高,‘亚德’幼果期果实中GR活性最高（0.06 μmol·min ^-1·g ^-1 FW）,之后随着果实的生长发育不断下降,抗坏血酸过氧化物酶（APX）活性变化与之相似;L-半乳糖途径的关键酶L-半乳糖-1,4-内酯脱氢酶（GalLDH）活性随着果实生长发育的变化趋势与AsA含量变化相一致,且‘亚德’果实中GalLDH活性在幼果期和成熟期均高于其他两个品种。通过相关性分析发现,GalLDH与T-AsA、AsA、DHA、DHAR和MDHAR呈现极显著正相关关系,相关系数可达0.91以上,即果实中GalLDH活性越高,果实中AsA含量也越高;DHAR和MDHAR与T-AsA、AsA间也存在极显著正相关关系,而APX与T-GSH、GSH间相关性较强。【结论】 黑穗醋栗幼果期果实中AsA含量最高,且品种间差异显著;GalLDH、MDHAR和DHAR可能是黑穗醋栗果实中AsA合成代谢的关键酶,黑穗醋栗果实中AsA含量积累主要取决于GalLDH活性,说明合成途径起着更关键的作用,而AsA-GSH循环再生途径相关酶对AsA合成也有一定的贡献,黑穗醋栗高AsA含量的积累是由合成途径与循环途径共同作用的结果。     

玉米大斑病菌甘油醛-3-磷酸脱氢酶基因克隆和表达分析

利用RT-PCR技术克隆玉米大斑病菌(Setosphaeria turcica)的GAPDH基因StGAPDH。该基因c DNA全长1 014 bp,编码337个氨基酸;蛋白质分子量36 505.44,理论pI值6.72,属弱酸、亲水、稳定蛋白,无跨膜结构域和信号肽。亚细胞定位于细胞质、线粒体和细胞核的概率分别为43.5%、30.4%和21.7%;氨基酸序列高度保守,在亲缘关系上与玉米小斑病菌(Bipolaris maydis)和水稻胡麻斑病菌(Bipolaris oryzae)最近。荧光定量PCR分析表明,在病菌接种抗病玉米自交系3 d时,StGAPDH基因表达量显著高于接种5～10 d(P<0.05);接种感病玉米自交系时,接种10 d的StGAPDH基因表达量显著高于接种3～7 d(P<0.05)。     

Molecular cloning,characterization and nutritional regulation of key enzymes required for the effective utilization of marine wax esters by Atlantic salmon (Salmo salar L.)

Previous studies had shown that wax ester‐rich lipid extracted from calanoid copepods could be a useful alternative to fish oil as a provider of long‐chain n‐3 polyunsaturated fatty acids in diets for use in salmon aquaculture. Effective utilization of wax ester requires digestion and metabolism in the intestine with the fatty alcohol component being oxidized to fatty acid in intestinal cells through the combined activities of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). We studied wax ester utilization in Atlantic salmon using a candidate gene approach, focusing on ADH and ALDH as sequence information was available for these genes, including fish sequences, facilitating isolation of the cDNAs. Here, we report on the isolation and cloning of full‐length cDNAs for ADH3 and ALDH3a2 genes from salmon intestinal tissue. Functional characterization by heterologous expression in the yeast, Saccharomyces cerevisiae, showed the products of these cDNAs had long‐chain ADH and ALDH enzyme activities. Thus, ADH3 was capable of oxidizing long‐chain fatty alcohol, and ALDH3a2 was capable of oxidizing long‐chain fatty aldehyde to the corresponding fatty acid. The genes were highly expressed in intestinal tissue, particularly pyloric caeca, but their expression was not increased in salmon fed dietary copepod oil in comparison to fish fed fish oil.     

纤维素酶催化水解和氧化机制的研究进展

人类对纤维素的开发与利用还非常有限,未能完全搞清天然纤维素的生物降解机制是其一个重要原因.自从C1-Cx假说提出以来,又有较多的降解理论出现对其改进,纤维素酶水解机制不能完全解释天然纤维素的降解,大量文献证实天然纤维素降解存在氧化机制.本文主要介绍水解与氧化机制中具代表性酶协同降解模型、纤维二糖水解酶(CBH)协同作用假说、羟基自由基的氧化机制和纤维二糖脱氢酶途径等不同降解理论,将水解和氧化两种机制结合起来给出其降解途径,也许能够较为容易理解纤维素的降解具体过程.     

Enzyme activity levels associated with the production of glycerol as an antifreeze in liver of rainbow smelt (Osmerus mordax)

Rainbow smelt (Osmerus mordax) tolerate temperatures close to the freezing point of sea water, in part, through the use of glycerol as an antifreeze. Potential mechanisms for glycerol production by liver were assessed by comparing activities of key enzym es of carbohydrate and amino acid metabolism in rainbow smelt to those in Atlantic tomcod (Microgadus tomcod) and smooth flounder (Liopsetta putmani). The latter two species inhabit the same environment but do not maintain high levels of blood glycerol. The enzyme profile of liver from rainbow smelt is substantially different from those of the other species and is poised for glycerol production. With respect to carbohydrate metabolism, glycerol-3-phosphate dehydrogenase activity in rainbow smelt liver was 156 µmoles min^-1 g^-1, a level which was 28 and 12-fold higher than activities in tomcod and flounder liver, respectively. Glycerol-3-phosphatase activity in smelt liver was 1.95 µmol min^-1 g^-1. This activity was 2.7 and 5.4-fold higher than those in tomcod and flounder liver, respectively. As such, the production of glycerol appears to be dependent upon the concerted action of glycerol-3-phosphate dehydrogenase and glycerol-3-phosphatase. The enzyme profile also suggests that amino acids are a potential source of carbon for glycerol. Aspartate aminotransferase activity in rainbow smelt was 7 to 14-fold higher in comparison to tomcod and flounder liver, respectively. Activities of alanine aminotransferase and glutamate dehydrogenase in liver were between 2 and 3-fold higher in rainbow smelt than in the other two species. Finally, it is shown that in vitro preparations of smelt liver sections produce glycerol at 0°C lending support to the concept that liver is a site of glycerol synthesis in vivo.     

紫果西番莲果实发育过程中挥发性香气物质及相关酶活性的变化

以西番莲香气物质较丰富的紫果‘台农1号’为试材,选取未成熟（T₁）、近成熟（T₂）和完全成熟（T₃）3个时期果实,采用顶空–固相微萃取–气质联用（HS-SPME-GC-MS）技术测定3个果实发育过程的挥发性香气物质组成及含量变化情况,同时检测对应果实中酯类香气物质合成相关的脂氧合酶（LOX）和醇酰基转移酶（AAT）活性,以期了解不同发育时期果实主要致香物质变化情况及物质与相关酶活性之间的相关性。结果表明：随着西番莲果实成熟度的增加,挥发性香气物质的种类和含量均有很大的提高,3个时期检测的香气物质总数分别为72种、95种和136种,总峰面积呈倍数增加;未成熟（T₁）和近成熟（T₂）2个时期萜烯类和酯类物质为主要的挥发性香气物质,在完全成熟（T₃）时期主要的挥发性香气为酯类,其峰面积占总峰面积达80.31%;随着果实成熟度的增加,酯类香气的种类和含量不断的提升,其中己酸乙酯,1-甲基己酯-己酸、丁酸乙酯、辛酸乙酯、1-甲基辛酯-丁酸、己酸己酯、1-甲基己酯-丁酸、丁酸己酯、(Z)-3-己烯基酯-己酸、乙酸己酯、2-甲基-辛酯-丙酸、辛酸己酯、3-羟基乙酯-己酸、(Z)-2-丁酸-乙酯等含量提升或占比较大,这些脂肪酸代谢途径产生的酯类在西番莲果实成熟过程中可能发挥了致香作用。LOX是酯类合成第一步的限速酶,AAT为酯类合成最后的关键酶。对不同发育期果实酯类合成相关酶活性测定结果表明,随着果实成熟度的增加,LOX、AAT酶活性呈上升趋势,尤其是T₃时期AAT酶活性显著的提升。由此推断,紫果西番莲果实发育过程中LOX和AAT酶的活性与酯类香气成分形成直接相关,酶活性的提升促进酯类香气的合成。