一种新ω-3脂肪酸脱饱和酶的克隆表达和活性鉴定

ω-3脂肪酸脱饱和酶催化ω-6多不饱和脂肪酸(PUFAs)转化为ω-3 PUFAs,对ω-3长链多不饱和脂肪酸(LC-PUFAs)的合成至关重要。为了实现在常温下发酵生产ω-3 LC-PUFAs(主要是二十碳五烯酸,EPA),根据现有常温下偏好催化20C PUFAs的ω-3脂肪酸脱饱和酶序列,从Gen Bank数据库筛选出与之高度相似的序列并进行生物信息学分析。为了确定序列的生物活性,进一步在酿酒酵母系统中进行重组表达,通过外源添加不同碳链长度的脂肪酸底物,测定重组酿酒酵母转化子在28℃和12℃下对不同脂肪酸的转化率。结果显示,新筛选序列编码的蛋白oAiFADS17既能催化18C PUFAs,又能催化20C PUFAs,尤其偏好催化二十碳四烯酸(AA)转化为EPA。oAiFADS17蛋白在28℃下对各种底物的转化率均高于12℃下的转化率,其中对AA的转化率达到46.3%。该研究成功测定了oAiFADS17蛋白对不同脂肪酸底物的转化率,得到了一种新的常温偏好催化20C PUFAs的ω-3脂肪酸脱饱和酶,为构建高产EPA的基因工程菌株及EPA的工业化生产奠定了理论基础。     

脂肪酶在食用油脂工业上的应用

脂肪酶按其对底物的特异性不同可分为非特异性酶、１,３—定向酶和脂肪酸特异性酶,在食用油脂工业上具有较大应用价值的是１,３—定向脂肪酶。介绍了脂肪酶（主要是１,３—定向脂肪酶）在油脂水解、酯交换和生物精炼三个方面的应用原理、特点及实例,从而展示出了脂肪酶催化技术在食用油脂工业上应用的前景     

产多不饱和脂肪酸微生物的研究

概述了微生物油脂的研究发展过程，列举了多不饱和脂肪酸（PUFAs）的生理功能、产PUFAs的菌株及其脂肪酸组成的特点？同时，介绍了多不饱和脂肪酸合成途径中的关键酶——脂肪酸脱饱和酶的基因研究情况，以及利用诱变育种技术、抗性筛选法、基因工程筛选等方法选育高产菌株的发展状况。     

聚硅氧烷的成膜性及其在纤维表面的排列

研究不同官能基聚硅氧烷的成膜性及其在纤维表面的定向排列方式。结果表明：氨基硅形成均匀、光滑的疏水膜。羧基硅形成有一定亲水性的非均匀膜，而聚醚/环氧硅油则形成极性亲水膜。     

食品加工环境胁迫因素对单核细胞增生李斯特菌生物膜形成的影响研究进展

单核细胞增生李斯特菌（以下简称单增李斯特菌）生物膜的生长可导致反复的食物污染。食品加工储藏常用的冷藏、干燥、酸处理以及消毒剂处理等使微生物长期处于胁迫环境下，对生物膜的形成产生影响。本文总结了常见的食品加工胁迫因素对单增李斯特菌生物膜形成的影响，其中重点介绍消毒剂处理对单增李斯特菌生物膜形成的影响，同时从膜流动性相关的适应策略、生物膜形成相关蛋白和基因调控表达的角度阐述胁迫条件下单增李斯特菌生物膜的形成机制。胁迫环境下单增李斯特菌生物膜形成的研究有助于揭示真实环境下其生物膜的形成及变化规律；充分考虑环境因素设定清洁、消毒标准有利于降低食源性致病菌传播的潜在风险。     

ω-6和ω-3多不饱和脂肪酸在仔猪前期料中应用探讨

ω-6和ω-3多不饱和脂肪酸(PUFAs)能够参与机体的抗炎性反应,减少免疫应激,因此在仔猪前期料中的应用也成为讨论热点。首先对脂肪酸的分类进行整理,通过对市场上仔猪前期料进行调研,并对其脂肪酸组成进行分析、讨论,根据已有的文献记载,阐述ω-6和ω-3 PUFAs抗炎性反应机理,并结合ω-6和ω-3 PUFAs在日粮中应用的研究进展,探讨ω-6和ω-3 PUFAs比值的应用。     

官能基聚硅氧烷的膜形态与定向排列方式

用原子力探针扫描电镜AFM等仪器对聚硅氧烷的膜形态及其排列方式作研究。结果表明：官能基聚硅氧烷在纤维表面定向排列形成的膜表面形态不同，氨基硅形成均一相疏水膜，羧基硅和聚醚／环氧硅油则形成形态学不均匀的膜。     

加工条件对亚油酸氧化形成呋喃的影响

呋喃是2B级致癌物（可能使人类致癌）,主要形成于食品热加工过程,多不饱和脂肪酸（PUFAs）氧化是形成呋喃的重要途径,然而PUFAs形成呋喃的研究尚处于起步阶段。本研究选用亚油酸为代表性脂肪酸,采用顶空进样-气相色谱-质谱联用法（HS-GC-MS）探究加工条件（温度、时间、pH值、含水量、金属离子、多酚）对亚油酸氧化形成呋喃的影响。结果表明,随着加热温度的升高和加热时间的延长,呋喃含量呈现增长趋势。随着水分添加量的增加（0～100μL）,促进效果呈先上升后降低最后趋于稳定的规律。添加Cu+、Cu2+和Fe3+等变价金属离子可显著促进亚油酸氧化形成呋喃（P <0.05）,而加入K+、Na+和Ca2+等金属离子对呋喃的形成没有显著影响。与中性条件相比,酸性条件对呋喃形成没有显著影响,而碱性条件可显著抑制呋喃的形成（P <0.05）,抑制率达56.64%。此外,添加多酚类物质,如表儿茶素没食子酸酯（ECG）、杨梅素、奎宁酸、对香豆酸、绿原酸可显著抑制呋喃的形成（P <0.05）,其中杨梅素抑制效果最好,抑制率最高可达55.54%。本研究结果可为脂质热加工过程中呋喃的调控提供...     

三相生物流化床处理中段废水时挂膜实验的研究

挂膜是生物流化床正常运行的关键。通过对生物流化床挂膜试验的研究发现 ,生物膜的形成可分为可逆附着、局部固定附着、生物膜的形成、生物膜脱落四步。活性炭吸附作用对挂膜初期COD的下降贡献很大。 2 4天后挂膜成功     

植－铝结合鞣机理的研究（Ⅵ）──模拟胶原和胶原试验

本次试验用聚己内酰胺模拟胶原的肽键作研究。结果表明，多元酚—铝与肽键基团能够发生作用（络台）。由于胶原的肽基众多，这种交联模式在植—铝结合鞣中成为重要的机理之一。除此之外，采用红外光谱法对胶原（皮粉）进行了研究。用鞣酸—铝处理胶原和变性胶原后，红外图谱分析的结果表明，鞣酸—铝与胶原的羧基、氨基和肽键区均能产生作用。正是这些结合，形成桥式交联和网状交联，才使得植—铝结合鞣革具有极高的湿热稳定性（收缩湿度高达１２０℃以上）。     

Endogenous production of n-3 and n-6 fatty acids in mammalian cells

Polyunsaturated fatty acids (PUFA) are important components of mammalian diets, and the beneficial effects of n-3 PUFA on human development and cardiovascular health have been well documented. Caenorhabditis elegans is one of the few animals known to be able to produce linoleic (LA, 18:2n-6) and alpha-linolenic (ALA, 18:3n-3) essential fatty acids. These essential PUFA are generated by the action of desaturases that successively direct the conversion of monounsaturated fatty acids (MUFA) to PUFA. The cDNA coding sequences of the C. elegans Delta(12) and n-3 fatty acid desaturases were each placed under the control of separate constitutive eukaryotic promoters and simultaneously introduced into HC11 mouse mammary epithelial cells by adenoviral transduction. Phospholipids from transduced cells showed a significant decrease in the ratios of both MUFA:PUFA and n-6:n-3 fatty acids relative to control cultures. The fatty acid profile of transduced cellular phospholipids revealed significant decreases in MUFA and arachidonic acid (20:4n-6), and increases in LA, ALA, and eicosapentaenoic acid (20:5n-3). The fatty acid composition of triacylglycerols derived from transduced cells was similarly, but less dramatically, affected. These results demonstrate the functionality of C. elegans fatty acid desaturase enzymes in mammalian cells. Expression of these desaturases in livestock might act to counterbalance the saturating effect that rumen microbial biohydrogenation has on the fatty acid profile of ruminant products, and allow for the development of novel, land-based dietary sources of n-3 PUFA.     

Δ12/Δ15脂肪酸脱饱和酶在发酵食品中应用的研究进展

Δ12/Δ15脂肪酸脱饱和酶在多不饱和脂肪酸合成中起重要作用，是生物体参与脂肪酸代谢途径的关键脱饱和酶类。脂肪酸在发酵食品中益生作用分析成为功能性脂质研究领域的热点话题，调控脂肪酸合成的Δ12/Δ15脂肪酸脱饱和酶应用的研究意义重大。本文首先介绍了Δ12/Δ15脂肪酸脱饱和酶及其参与的脂肪酸代谢途径，其次从植物、动物、细菌、酵母菌、霉菌和藻类6 个方面简述Δ12/Δ15脂肪酸脱饱和酶来源，综述了Δ12/Δ15脂肪酸脱饱和酶在发酵食品应用中的研究，旨在为Δ12/Δ15脂肪酸脱饱和酶研究提供一定的理论参考，为Δ12/Δ15脂肪酸脱饱和酶在发酵食品工业的应用提供新思路。     

Identification and characterization of a novel yeast omega3-fatty acid desaturase acting on long-chain n-6 fatty acid substrates from Pichia pastoris

A cDNA sequence putatively encoding a omega(3)-fatty acid desaturase gene was isolated from methylotrophic yeast Pichia pastoris GS115. The deduced amino acid sequence of this cloned cDNA showed high identity to known fungal omega(3)-fatty acid desaturases. Functional identification of this gene heterologously in Saccharomyces cerevisiae strain INVScl indicated that the deduced amino acid sequence exhibited omega(3)-fatty acid desaturase activity. The newly identified omega(3)-fatty acid desaturase, named Pp-FAD3, is novel because it showed broad n-6 fatty acid substrate specificity by its ability to convert all the 18-carbon and 20-carbon n-6 substrates examined to the corresponding n-3 fatty acids, with an approximately equivalent high conversion rate. Pp-FAD3 is the first known yeast omega(3)-fatty acid desaturase to act on long-chain n-6 fatty acid substrates. Heterologous expression of the newly identified omega(3) desaturase in different hosts will be an alternative method to increase the flow of n-6 fatty acid intermediates into their n-3 derivatives.     

Assessment and profiling of the fatty acids in two ackee fruit (Blighia sapida Köenig) varieties during different ripening stages

BACKGROUND: The ripening of fruits is characterized by physical, chemical and biochemical compositional changes such as color, sugars and phenolic compounds. Ackee fruit is famous in Jamaica and the Caribbean. This study aimed to assess the variation of fatty acids in two varieties (cheese and butter) ackee (Blighia sapida) fruits during five different ripening stages. RESULTS: The total fatty acid content of ackee fruit was much higher in arils and ranged from 283.4 to 465.1 g kg^?1 dry weight (DW), while in husk they ranged from 235.2 to 465.1 g kg^?1 DW in both varieties. Total fatty acid content declined in the arils and the husks as the fruit ripened. Five major fatty acids were found: palmitic acid (C16:0) and stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). In the arils, oleic acid was found at the highest concentration, followed by palmitic, stearic, linoleic and last linolenic acid. The unsaturated:saturated ratio of fatty acids varied from 1.23 to 3.26 in the arils of both varieties, and from 1.03 to 5.05 in the husk. Monounsaturated:polyunsaturated fatty acids ranged from 8.56 to 25.19 in the arils and from 0.62 to 2.33 in the husk. CONCLUSION: The results show that ackee arils contain much higher levels of fats than the husk and the major fatty acid in the arils was oleic acid (Δ9‐cis‐oleic acid, an omega n‐9), while in the husk unsaturated fatty acids were higher than the saturated ones. Oleic acid was the major fatty acid in both varieties, and aril fatty acid content was 10–20 times higher than in the husk. In both varieties, unsaturated fatty acids were relatively higher than saturated ones; however, total fatty acids showed a decline with ripening for arils and husk tissues. © 2012 Society of Chemical Industry     

乳甘油三酯的组成结构及其消化吸收和代谢特性

甘油三酯(triacylglycerols,TAGs)是膳食中最重要的脂质成分,不仅为人体提供能量同时也是多种必需脂肪酸的重要来源。甘油三酯的消化、吸收和代谢受到多种因素的影响。大量研究结果证实除脂肪酸的组成以外,甘油三酯的组成和结构对脂肪酸的吸收和代谢也有显著的影响。乳甘油三酯与其他膳食脂肪相比具有特殊的组成和结构,这些特异性使得乳甘油三酯具有许多特殊的生理和营养学功能。本文详细阐述了人乳、牛乳和山羊乳甘油三酯的结构特征,甘油三酯消化、吸收和脂肪酸代谢过程,以及甘油三酯分子内结构对其代谢的作用的影响,以期为甘油三酯代谢、营养及功能特性研究提供参考。     

红烧肉制作过程中脂肪氧化和脂肪酸组成的变化

脂肪氧化和脂肪酸组成变化对肉制品的营养和风味产生重要影响。研究红烧肉烹制全过程中原料、水焯后、炖煮1h、炖煮2h 4个关键工艺点中猪肉的基本物理化学指标、脂肪氧化和脂肪酸组成变化情况。结果表明：成品红烧肉水分含量和粗脂肪含量分别比原料肉下降18.17%和43.46%,烹饪损失率为25.04%;过氧化值(POV)在炖煮1h后达到峰值,随后又下降;硫代巴比妥酸值(TBA)在烹制过程中逐渐上升(P＜0.05);烹制过程使饱和脂肪酸(SFA)比例显著下降(P＜0.05),单不饱和脂肪酸(MUFA)比例显著上升(P＜0.05),不饱和脂肪酸与饱和脂肪酸比值(UFA/SFA)从1.38上升到2.34,提高了猪肉中油脂的营养价值。     

Generation of glycerophospholipid molecular species in the yeast Saccharomyces cerevisiae. Fatty acid pattern of phospholipid classes and selective acyl turnover at sn-1 and sn-2 positions

Acyl chains linked to phospholipids of the yeast, Saccharomyces cerevisiae, are mainly C16:1 and C18:1 accompanied by minor amounts of C14:0, C16:0 and C18:0. In view of this rather simple fatty acid composition, the question arose whether in yeast, as in higher eukaryotes, fatty acyl groups were characteristically distributed among the sn-1 and sn-2 positions of distinct phospholipid classes. Analysis of fatty acids linked to the sn-1 and sn-2 positions of the major phospholipids showed that indeed saturated fatty acyl groups predominated in the sn-1 positions. While the percentage of saturated fatty acids was low (10%) in phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) from cells grown on rich medium, it was higher in phosphatidylserine (PtdSer) (25%) and highest in phosphatidylinositol (PtdIns) (41%). Oleate was mainly linked to position sn-2, while palmitoleate predominated in position sn-1. Striking differences in the fatty acid distribution of phospholipids that are metabolically closely related (e.g. PtdSer and PtdEtn, PtdEtn and PtdCho, and PtdIns and PtdSer) suggest that pathways must exist for the generation of distinct phospholipid molecular species within the different phospholipid classes. The highly selective incorporation of exogenous [¹⁴C]palmitic acid (90%) and [³H]oleic acid (99%) into the sn-2 position of PtdCho, and the preferential incorporation of these fatty acids into the sn-2 position of PtdEtn (70 and 90%, respectively, for palmitic and oleic acid) are compatible with the postulate that phospholipase A₂-mediated deacylation followed by reacylation of the lysophospholipids is involved in the generation of phospholipid species in yeast.     

Seasonal variation in the fatty acid composition of milk available at retail in the United Kingdom and implications for dietary intake

Milk and dairy products are major sources of fat in the human diet, but there are few detailed reports on the fatty acid composition of retail milk, trans fatty acids in particular, and how these change throughout the year. Semi-skimmed milk was collected monthly for one year from five supermarkets and analysed for fatty acid composition. Relative to winter, milk sold in the summer contained lower total saturated fatty acid (SFA; 67 vs 72 g/100 g fatty acids) and higher cis-monounsaturated fatty acid (MUFA; 23 vs 21 g/100 g fatty acids) and total trans fatty acid (6.5 vs 4.5 g/100 g fatty acids) concentrations. Concentrations of most trans-18:1 and -18:2 isomers also exhibited seasonal variation. Results were applied to national dietary intakes, and indicated that monthly variation in the fatty acid composition of milk available at retail has limited influence on total dietary fatty acid consumption by UK adults.     

Trans Fatty Acid Content of Selected Foods in an African-American Community

ABSTRACT:  Trans fatty acid content was examined in several grocery foods and fast foods in an African-American community. Food samples were selected based on the frequency of use among this population group in the local community. Samples were collected 3 times with an interval of 1 wk. Total fat content was analyzed by Soxhlet method. Fatty acids profile, including trans fatty acids, was analyzed by GC–MS. In grocery foods, no trans fatty acids were detected in fish sticks, salad dressing, mayonnaise, muffin, and potato chips. Margarine contained the highest trans fatty acid at a level of 19.13%. The trans fatty acid level in crackers, cookies, butter, chicken patties, and biscuits mix ranged from 0.51% to 1.77%. In fast foods, no trans fat was detected in dressing. All the fried food and bakery food sampled in this study contain trans fat. The level varied from 2.07% to 10.30%. The principal trans fatty acid was trans 18:1. Other trans fatty acids found were trans 18:2, trans 19:1, and trans 16:1. In a total of 23 food samples, 16 of them were found to contain trans fatty acid. The results demonstrated that trans fat is commonly found in foods of the African-American community. The trans fatty acids content in tested samples varied from 0% to 19.13%.     

气相色谱法测定常见植物油中脂肪酸

随着营养学研究发展,人们对脂肪酸认识不断增加。中国营养学会也推荐膳食中必需脂肪酸摄入理想比值,市场上也出现大量调和油,为了评估食用植物油营养价值,该研究分析常用食用植物油中脂肪酸组成和各种油营养特色。方法:用氢氧化钾-甲醇溶液将植物油皂化后,在三氟化硼作为催化剂作用下,用甲醇将样品甲酯化,正己烷提取甲酯化产物。以毛细管柱DB-23作为分离柱,用气相色谱法测定植物油脂肪酸组成。结果:大豆油,葵花籽油,玉米油中含有50％-60％亚油酸和20％-30％油酸,营养均衡合理;花生油,芝麻油中油酸、亚油酸含量约35％-45％,易于人体吸收;菜籽油中含有45％油酸和15％芥酸,芥酸对人体健康有不利作用;橄榄油,茶籽油中含有75％-80％油酸,红花籽油中含有约80％亚油酸,有降低胆固醇功效。